JP3509514B2 - Method of manufacturing gallium nitride based compound semiconductor - Google Patents

Method of manufacturing gallium nitride based compound semiconductor

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Publication number
JP3509514B2
JP3509514B2 JP33094497A JP33094497A JP3509514B2 JP 3509514 B2 JP3509514 B2 JP 3509514B2 JP 33094497 A JP33094497 A JP 33094497A JP 33094497 A JP33094497 A JP 33094497A JP 3509514 B2 JP3509514 B2 JP 3509514B2
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JP
Japan
Prior art keywords
layer
heat treatment
compound semiconductor
gallium nitride
metal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
JP33094497A
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Japanese (ja)
Other versions
JPH11145518A (en
Inventor
潤 伊藤
直樹 柴田
俊也 上村
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Toyoda Gosei Co Ltd
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Toyoda Gosei Co Ltd
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0062—Processes for devices with an active region comprising only III-V compounds
    • H01L33/0066—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound
    • H01L33/007—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound comprising nitride compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
    • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen
    • H01L33/325—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen characterised by the doping materials

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  • Electrodes Of Semiconductors (AREA)
  • Semiconductor Lasers (AREA)
  • Led Devices (AREA)

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【発明の属する技術分野】本発明は、窒化ガリウム(Ga
N) 系化合物半導体の製造方法において、特に、低抵抗
なｐ型層を形成する方法に関する。TECHNICAL FIELD The present invention relates to gallium nitride (Ga
In particular, the present invention relates to a method for forming a low-resistance p-type layer in a method for producing an N) -based compound semiconductor.

【０００２】[0002]

【従来の技術】従来、短波長発光デバイス材料として用
いられるGaN をｐ型化する方法としては、例えばマグネ
シウム(Mg)などのｐ型不純物をドーピングしたGaN に対
して、電子線照射処理又は窒素雰囲気で熱処理する方法
が知られている。2. Description of the Related Art Conventionally, as a method for converting p-type GaN used as a short-wavelength light emitting device material, for example, GaN doped with p-type impurities such as magnesium (Mg) is subjected to electron beam irradiation treatment or a nitrogen atmosphere. A method of heat treatment is known.

【０００３】[0003]

【発明が解決しようとする課題】通常、アクセプタ不純
物をドーピングしただけのGaN では、ｐ型不純物原子と
水素原子とが結合しているために、ｐ型不純物原子がア
クセプタとして機能せず、このｐ型不純物原子をアクセ
プタとして機能させるためには、熱処理温度を700 ℃以
上の高温にしてｐ型不純物原子と水素原子とを解離させ
る必要がある。半導体に対する高温の熱処理は半導体層
内部への熱的ダメージを与えると同時に表面モフォロジ
ーの悪化を招くため、熱処理温度の低温化が求められて
いる。Normally, in GaN simply doped with an acceptor impurity, the p-type impurity atom does not function as an acceptor because the p-type impurity atom and the hydrogen atom are bonded to each other. In order for the type impurity atoms to function as acceptors, it is necessary to raise the heat treatment temperature to 700 ° C. or higher to dissociate the p type impurity atoms and hydrogen atoms. A high temperature heat treatment for a semiconductor causes thermal damage to the inside of the semiconductor layer, and at the same time causes deterioration of the surface morphology. Therefore, a lower heat treatment temperature is required.

【０００４】従って、本発明の目的は、熱処理の低温化
を実現することである。Therefore, an object of the present invention is to realize a low temperature heat treatment.

【０００５】[0005]

【課題を解決するための手段】上記の課題を解決するた
めに、請求項１に記載の手段によれば、ｐ型のGaN 系化
合物半導体を製造する方法において、アクセプタ不純物
の添加されたGaN 系化合物半導体の表面に金属から成る
薄膜を形成した後、熱処理を行う。これにより、薄膜を
構成する金属原子が、熱処理時にアクセプタ不純物の添
加されたGaN 系化合物半導体中の水素を引き抜いて還元
反応を起こすため、不純物がアクセプタとして機能し、
GaN 系化合物半導体中のｐ型化が促進され、内部までｐ
型化でき、低抵抗なｐ型半導体を得ることができる。
又、熱処理の低温化が可能となり、高温域での表面モフ
ォロジーの劣化を防止できる。更に、熱処理の後に、金
属薄膜を除去し、 GaN 系化合物半導体上に電極が形成さ
れることにより、アロイ温度を最適化できるので駆動電
圧を低下することができる。 In order to solve the above-mentioned problems, according to the means of claim 1, in a method for producing a p-type GaN compound semiconductor, a GaN compound having an acceptor impurity added thereto is added. After forming a thin film made of metal on the surface of the compound semiconductor, heat treatment is performed. As a result, the metal atoms forming the thin film extract hydrogen from the GaN-based compound semiconductor to which the acceptor impurity was added during the heat treatment to cause a reduction reaction, and the impurity functions as an acceptor.
Promoting p-type conversion in GaN-based compound semiconductors
It is possible to obtain a p-type semiconductor that can be formed into a mold and has low resistance.
Further, the heat treatment can be performed at a low temperature, and the deterioration of the surface morphology in the high temperature region can be prevented. Furthermore, after heat treatment, gold
The metal thin film is removed, and an electrode is formed on the GaN compound semiconductor.
The alloy temperature can be optimized by
The pressure can be reduced.

【０００６】請求項２に記載の手段によれば、少なくと
も酸素(O) を含む雰囲気中で熱処理が行われることによ
り、GaN 中から引き抜かれたH と酸化された金属とが反
応しH2O のような形でH を気相中へ逃がすことによって
金属原子が還元されるが、この金属原子が雰囲気中の酸
素により再び酸化されて水素引き抜き反応を生じさせる
ことが可能になるので、低抵抗化がより促進される。結
果的に、熱処理をより低温で行うことことができる。
尚、ここでいう酸素を含む雰囲気とは、例えばO2、O3、
CO、CO2 、NO、N2O 、NO2 、又は、H2O の少なくとも１
種又はこれらの混合ガス、又は、O2、O3、CO、CO2 、N
O、N2O 、NO2 、又は、H2O の少なくとも１種と不活性
ガスとの混合ガス、又は、O2、O3、CO、CO2 、NO、N2O
、NO2 、又は、H2O の混合ガスと不活性ガスとの混合
ガス等を用いることをいう。According to the second aspect, the heat treatment is performed in the atmosphere containing at least oxygen (O), whereby H extracted from GaN reacts with the oxidized metal to generate H 2 O. By releasing H 2 into the gas phase in a form such as, the metal atom is reduced, but this metal atom can be oxidized again by the oxygen in the atmosphere to cause the hydrogen abstraction reaction, so the resistance is low. Is promoted further. As a result, the heat treatment can be performed at a lower temperature.
The oxygen-containing atmosphere here means, for example, O 2 , O 3 ,
At least one of CO, CO 2 , NO, N 2 O, NO 2 or H 2 O
Seed or mixed gas of these, or O 2 , O 3 , CO, CO 2 , N
Mixed gas of at least one of O, N 2 O, NO 2 or H 2 O and an inert gas, or O 2 , O 3 , CO, CO 2 , NO, N 2 O
, NO 2 , or a mixed gas of H 2 O and an inert gas is used.

【０００７】請求項３に記載の手段によれば、薄膜を構
成する金属は、コバルト(Co)、ニッケル(Ni)、アルミニ
ウム(Al)、銅(Cu)、パラジウム(Pd)、マンガン(Mn)、バ
ナジウム(V) 及び金(Au)のうち少なくとも１種より成る
ことにより、請求項２に記載の手段を具体的に実現でき
る。According to the means of claim 3, the metal constituting the thin film is cobalt (Co), nickel (Ni), aluminum (Al), copper (Cu), palladium (Pd), manganese (Mn). The means according to claim 2 can be concretely realized by comprising at least one of :, vanadium (V) and gold (Au).

【０００８】請求項４に記載の手段によれば、薄膜が5
〜3000Åの膜厚に形成されることにより、GaN 系化合物
半導体を効果的に低抵抗化できる。According to the means of claim 4, the thin film is 5
By forming a film thickness of ~ 3000Å, it is possible to effectively reduce the resistance of the GaN compound semiconductor.

【０００９】[0009]

【００１０】[0010]

【発明の実施の形態】以下、本発明を具体的な実施例に
基づいて説明する。図１は、サファイア基板１上に形成
されたGaN 系化合物半導体発光素子１０の断面構成を示
した模式図である。サファイア基板１の上には AlNから
成る膜厚約25nmのバッファ層２が設けられ、その上にSi
ドープの膜厚約４μｍのｎ型GaN 層３が形成されてい
る。このｎ型GaN 層３の上に膜厚約35ÅのGaN から成る
バリア層４１と膜厚約35ÅのGa0.8In0.2N から成る井戸
層４２とが交互に積層された多重量子井戸構造（ＭＱ
Ｗ）の発光層４が形成されている。バリア層４１は６
層、井戸層４２は５層である。発光層４の上には膜厚約
250nm のｐ型GaN 層５が形成されている。ｐ型GaN 層５
の上には金属蒸着による膜厚約15ÅのCoから成る第１金
属層６１と、膜厚約60ÅのAuから成る第２金属層６２と
が順次積層され、この第１金属層６１と第２金属層６２
とで透光性のｐ電極６が構成されている。このｐ電極６
上の所定領域に、CoもしくはNiとAu、Al、又はそれらの
合金から成る膜厚約1.5 μｍの電極パッド７が形成され
ている。又、ｎ型GaN 層３上には、膜厚約 200Åのバナ
ジウム(V) と膜厚約 1.8μｍのアルミニウム(Al)又はAl
合金で構成されたｎ電極８が形成されている。BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on specific embodiments. FIG. 1 is a schematic view showing a cross-sectional structure of a GaN-based compound semiconductor light emitting device 10 formed on a sapphire substrate 1. A buffer layer 2 made of AlN and having a thickness of about 25 nm is provided on the sapphire substrate 1, and Si is formed on the buffer layer 2.
An n-type GaN layer 3 having a film thickness of about 4 μm is formed. A multi-quantum well structure (MQ, in which a barrier layer 41 made of GaN having a film thickness of about 35Å and a well layer 42 made of Ga 0.8 In 0.2 N having a film thickness of about 35Å are alternately laminated on the n-type GaN layer 3
The light emitting layer 4 of W) is formed. 6 barrier layers 41
The number of layers and well layers 42 is five. About the film thickness on the light emitting layer 4
A 250 nm p-type GaN layer 5 is formed. p-type GaN layer 5
A first metal layer 61 made of Co having a film thickness of about 15 Å and a second metal layer 62 made of Au having a film thickness of about 60 Å are sequentially laminated on the first metal layer 61 and the second metal layer 61. Metal layer 62
And form a translucent p-electrode 6. This p electrode 6
An electrode pad 7 made of Co or Ni and Au, Al, or an alloy thereof and having a film thickness of about 1.5 μm is formed in the predetermined region above. Also, on the n-type GaN layer 3, vanadium (V) with a film thickness of about 200Å and aluminum (Al) or Al with a film thickness of about 1.8 μm are used.
An n electrode 8 made of an alloy is formed.

【００１１】次に、この発光素子１０の製造方法につい
て説明する。上記発光素子１０は、有機金属気相成長法
（以下「MOVPE 」と略す）による気相成長により製造さ
れた。用いられたガスは、アンモニア(NH3) 、キャリア
ガス(H2,N2) 、トリメチルガリウム(Ga(CH3)3)（以下
「TMG 」と記す）、トリメチルアルミニウム(Al(CH3)3)
（以下「TMA 」と記す）、トリメチルインジウム(In(CH
3)3)（以下「TMI 」と記す）、シラン(SiH4)とシクロペ
ンタジエニルマグネシウム(Mg(C5H5)2) （以下「CP2Mg
」と記す）である。Next, a method of manufacturing the light emitting device 10 will be described. The light emitting device 10 was manufactured by vapor phase epitaxy by a metal organic vapor phase epitaxy method (hereinafter abbreviated as “MOVPE”). The gas used was ammonia (NH 3 ), carrier gas (H 2 , N 2 ), trimethylgallium (Ga (CH 3 ) 3 ) (hereinafter referred to as “TMG”), trimethylaluminum (Al (CH 3 ) 3 )
(Hereinafter referred to as "TMA"), trimethylindium (In (CH
3) 3) (hereinafter referred to as "TMI"), silane (SiH 4) and cyclopentadienyl magnesium (Mg (C 5 H 5) 2) ( hereinafter "CP 2 Mg
]).

【００１２】まず、有機洗浄及び熱処理により洗浄した
ａ面を主面とした単結晶のサファイア基板１をMOVPE 装
置の反応室に載置されたサセプタに装着する。次に、常
圧でH2を流速 2liter/分で約30分間反応室に流しながら
温度1100℃でサファイア基板１をベーキングした。次
に、温度を400 ℃まで低下させて、H2を20liter/分、NH
3 を10liter/分、TMA を1.8 ×10-5モル／分で供給して
AlN のバッファ層２を約25nmの膜厚に形成した。First, the single crystal sapphire substrate 1 whose main surface is the a-plane cleaned by organic cleaning and heat treatment is mounted on a susceptor placed in a reaction chamber of a MOVPE apparatus. Next, the sapphire substrate 1 was baked at a temperature of 1100 ° C. while flowing H 2 into the reaction chamber at a flow rate of 2 liter / min for about 30 minutes under normal pressure. Then the temperature is lowered to 400 ° C and H 2 is added to 20 liter / min NH
3 at 10 liter / min and TMA at 1.8 × 10 -5 mol / min
The AlN buffer layer 2 was formed to a film thickness of about 25 nm.

【００１３】次に、サファイア基板１の温度を1150℃に
保持し、N2又はH2を10liter/分、NH3 を10liter/分、TM
G を1.12×10-4モル／分、TMA を0.47×10-4モル／分、
H2ガスにより0.86ppm に希釈されたシランを 5×10-9モ
ル／分で供給して、膜厚約４μｍ、電子濃度 1×1018/c
m3、シリコン濃度 2×1018/cm3のｎ型GaN 層３を形成し
た。上記のｎ型GaN 層３を形成した後、続いて、N2又は
H2を20liter/分、NH3 を10liter/分、TMG を2.0 ×10-4
モル／分で供給して、膜厚約35ÅのGaN から成るバリア
層４１を形成した。次に、N2又はH2、NH3 の供給量を一
定として、TMG を7.2 ×10-5モル／分、TMI を0.19×10
-4モル／分で供給して、膜厚約35ÅのGa0.8In0.2N から
成る井戸層４２を形成した。さらに、バリア層４１と井
戸層４２を同一条件で５周期形成し、その上にGaN から
成るバリア層４１を形成した。このようにして５周期の
ＭＱＷ構造の発光層４を形成した。Next, the temperature of the sapphire substrate 1 is kept at 1150 ° C., N 2 or H 2 is 10 liter / min, NH 3 is 10 liter / min, and TM
G is 1.12 × 10 -4 mol / min, TMA is 0.47 × 10 -4 mol / min,
Silane diluted to 0.86 ppm with H 2 gas was supplied at 5 × 10 -9 mol / min to obtain a film thickness of about 4 μm and electron concentration of 1 × 10 18 / c.
m 3, to form an n-type GaN layer 3 of silicon concentration 2 × 10 18 / cm 3. After forming the above n-type GaN layer 3, N 2 or
20 liters / min for H 2 , 10 liters / min for NH 3 , 2.0 × 10 -4 for TMG
The barrier layer 41 made of GaN and having a film thickness of about 35 Å was formed by supplying at a rate of mol / min. Next, with the feed rates of N 2 or H 2 and NH 3 being constant, TMG was 7.2 × 10 -5 mol / min and TMI was 0.19 × 10 5.
It was supplied at -4 mol / min to form a well layer 42 of Ga 0.8 In 0.2 N with a film thickness of about 35 Å. Further, the barrier layer 41 and the well layer 42 were formed under the same condition for 5 periods, and the barrier layer 41 made of GaN was formed thereon. In this way, the light emitting layer 4 having the MQW structure of 5 cycles was formed.

【００１４】次に、サファイア基板１の温度を1100℃に
保持し、N2又はH2を20liter/分、NH3 を10liter/分、TM
G を1.12×10-4モル／分、CP2Mg を 2×10-5モル／分で
供給して、膜厚約250nm 、濃度 5×1019/cm3のMgをドー
プしたｐ型GaN 層５を形成した。そのｐ型GaN 層５上に
Coを厚さ100 Å（真空度10-3Paオーダーで蒸着）に形成
し、その後O2ガスを供給し、圧力10Pa、約650 ℃で６分
程度加熱した。次にCoを硝酸系エッチング液で除去し
た。次に、ｐ型GaN 層５上にエッチングマスクを形成
し、所定領域のマスクを除去して、マスクで覆われてい
ない部分のｐ型GaN 層５、発光層４及びｎ型GaN 層３の
一部を塩素を含むガスによる反応性イオンエッチングに
よりエッチングして、ｎ型GaN 層３の表面を露出させ
た。次に、以下の手順で、ｎ型GaN 層３に対するｎ電極
８とｐ型GaN 層５に対する透光性のｐ電極６とを形成し
た。Next, the temperature of the sapphire substrate 1 is maintained at 1100 ° C., N 2 or H 2 is 20 liter / min, NH 3 is 10 liter / min, and TM
A p-type GaN layer doped with Mg at a thickness of about 250 nm and a concentration of 5 × 10 19 / cm 3 by supplying G at 1.12 × 10 -4 mol / min and CP 2 Mg at 2 × 10 -5 mol / min. 5 was formed. On the p-type GaN layer 5
Co was formed to a thickness of 100 Å (vapor deposition at a vacuum degree of 10 -3 Pa order), and then O 2 gas was supplied, and heated at a pressure of 10 Pa at about 650 ° C for about 6 minutes. Next, Co was removed with a nitric acid-based etching solution. Next, an etching mask is formed on the p-type GaN layer 5, the mask in a predetermined region is removed, and one of the p-type GaN layer 5, the light-emitting layer 4, and the n-type GaN layer 3 which is not covered with the mask is removed. The portion was etched by reactive ion etching using a gas containing chlorine to expose the surface of the n-type GaN layer 3. Next, the n electrode 8 for the n-type GaN layer 3 and the translucent p-electrode 6 for the p-type GaN layer 5 were formed by the following procedure.

【００１５】(1) フォトレジストを塗布し、フォトリソ
グラフィによりｎ型GaN 層３の露出面上の所定領域に窓
を形成して、10-3Paオーダ以下の高真空に排気した後、
膜厚約 200Åのバナジウム(V) と膜厚約 1.8μｍのAlを
蒸着した。次に、フォトレジストを除去する。これによ
りｎ型GaN 層３の露出面上にｎ電極８が形成される。 (2) 次に、表面上にフォトレジストを一様に塗布して、
フォトリソグラフィにより、ｐ型GaN 層５の上のフォト
レジストを除去して、窓部を形成する。 (3) 蒸着装置にて、フォトレジスト及び露出させたｐ型
GaN 層５上に、10-3Paオーダ以下の高真空に排気した
後、膜厚約15ÅのCoを成膜させて、第１金属層６１を形
成する。 (4) 続いて、第１金属層６１の上に膜厚約60ÅのAuを成
膜させて、第２金属層６２を形成する。(1) A photoresist is applied, a window is formed in a predetermined region on the exposed surface of the n-type GaN layer 3 by photolithography, and after evacuation to a high vacuum of the order of 10 -3 Pa or less,
Vanadium (V) with a film thickness of about 200Å and Al with a film thickness of about 1.8 μm were deposited. Next, the photoresist is removed. As a result, the n-electrode 8 is formed on the exposed surface of the n-type GaN layer 3. (2) Next, apply photoresist uniformly on the surface,
The photoresist on the p-type GaN layer 5 is removed by photolithography to form a window. (3) Photo-resist and exposed p-type in vapor deposition equipment
After evacuating to a high vacuum of the order of 10 −3 Pa or less on the GaN layer 5, Co having a film thickness of about 15 Å is formed to form the first metal layer 61. (4) Subsequently, Au having a film thickness of about 60 Å is formed on the first metal layer 61 to form the second metal layer 62.

【００１６】(5) 次に、試料を蒸着装置から取り出し、
リフトオフ法によりフォトレジスト上に堆積したCo、Au
を除去する。 (6) 次に、透光性のｐ電極６上の一部にボンディング用
の電極パッド７を形成するために、フォトレジストを一
様に塗布して、その電極パッド７の形成部分のフォトレ
ジストに窓を開ける。次に、CoもしくはNiとAu、Al、又
は、それらの合金を膜厚1.5 μｍ程度に、蒸着により成
膜させ、(5) の工程と同様に、リフトオフ法により、フ
ォトレジスト上に堆積したCoもしくはNiとAu、Al、又は
それらの合金から成る膜を除去して、電極パッド７を形
成する。 (7) その後、試料雰囲気を真空ポンプで排気し、O2ガス
を供給して圧力 3Paとし、その状態で雰囲気温度を約 5
50℃にして、3 分程度、加熱し、ｐ型GaN 層５と第１金
属層６１と第２金属層６２との合金化処理、ｎ電極８と
ｎ型GaN 層３との合金化処理を行った。(5) Next, the sample is taken out from the vapor deposition device,
Co and Au deposited on photoresist by lift-off method
To remove. (6) Next, in order to form an electrode pad 7 for bonding on a part of the translucent p-electrode 6, a photoresist is uniformly applied, and the photoresist of the part where the electrode pad 7 is formed is formed. Open the window. Next, Co or Ni and Au, Al, or an alloy thereof is deposited to a film thickness of about 1.5 μm by vapor deposition, and Co is deposited on the photoresist by the lift-off method as in the step (5). Alternatively, the electrode pad 7 is formed by removing the film made of Ni and Au, Al, or an alloy thereof. (7) After that, the sample atmosphere was evacuated by a vacuum pump, O 2 gas was supplied to make the pressure 3 Pa, and the atmospheric temperature was kept at about 5 Pa.
After heating to 50 ° C. for about 3 minutes, alloying treatment of the p-type GaN layer 5, first metal layer 61 and second metal layer 62, and n-electrode 8 and n-type GaN layer 3 are performed. went.

【００１７】上記方法により得られた発光素子１０は、
従来に比較して低温（約650 ℃）でｐ型GaN 層５の低抵
抗化ができ、電極との合金化処理を最適温度の約550 ℃
で行うことにより、従来に比較して駆動電圧を低減する
ことが可能となった。The light emitting device 10 obtained by the above method is
The p-type GaN layer 5 can be made lower in resistance at a lower temperature (about 650 ° C) than before, and the alloying process with the electrode is optimal at about 550 ° C.
By doing so, it becomes possible to reduce the drive voltage as compared with the conventional case.

【００１８】図２は、キャリア濃度及び導電率を測定す
るために用いたサンプル２０である。サファイア基板１
上には、図１の構成と同じ組成から成るバッファ層２、
ｐ型GaN 層５が形成されている。層５にCo金属を100 Å
の厚さに形成し、各温度にて６分間熱処理を行った後、
王水で処理して金属層を除去し、四隅に膜厚約3000Åの
ニッケル(Ni)９を蒸着して、測定を行った。又、比較対
象のために金属層を設けずに同様に処理した場合につい
ても測定した。FIG. 2 is a sample 20 used to measure carrier concentration and conductivity. Sapphire substrate 1
Above it is a buffer layer 2 of the same composition as in FIG.
A p-type GaN layer 5 is formed. Co metal 100 Å for layer 5
Thickness and after heat treatment for 6 minutes at each temperature,
The treatment was carried out with aqua regia to remove the metal layer, and nickel (Ni) 9 having a film thickness of about 3000 Å was vapor-deposited on the four corners for measurement. Also, the measurement was performed for the case where the same treatment was performed without providing a metal layer for comparison.

【００１９】図３は、図２のサンプル２０を用いて、熱
処理温度とキャリア濃度との関係を示した特性図であ
る。この図では、○印及び●印が熱処理時に金属層を設
けた場合の結果を示し、□印及び■印が熱処理時に金属
層を設けない場合を示している。これにより、金属層を
設けて熱処理することによって、キャリア濃度が高ま
り、ｐ型化が促進されることがわかる。これは、金属層
が、熱処理時にｐ型GaN 層５から水素を引き抜いて還元
反応を生じるためにｐ型GaN 層５の低抵抗化が促進され
るためである。又、金属層を設けた結果のうち○印が、
O2雰囲気中で熱処理を行った結果を示し、●印がN2雰囲
気中で熱処理を行った結果を示すが、O2雰囲気中で熱処
理を行う方が、N2雰囲気中で行うよりキャリア濃度が高
い、即ちｐ型化が促進されていることがわかる。O2雰囲
気中で約550 ℃の熱処理により約1 ×1017/cm3のキャリ
ア濃度が得られ、約500 ℃の熱処理では約1 ×1014/cm3
のキャリア濃度が得られる。これは、O2雰囲気中で熱処
理することにより、前述の酸化還元反応によりｐ型GaN
層５から水素を引き抜いて連続した酸化還元反応によっ
て、ｐ型GaN 層５の低抵抗化が促進されるからである。
よって、O2雰囲気を用いることにより、約650 ℃の熱処
理で1 ×1018/cm3と最も高いキャリア濃度を得ることが
可能である。一方、その他の場合は更なる高温条件が必
要とされ、キャリア濃度は、金属層形成後にO2雰囲気で
熱処理した場合のキャリア濃度まで到達しなかった。FIG. 3 is a characteristic diagram showing the relationship between the heat treatment temperature and the carrier concentration using the sample 20 of FIG. In this figure, the circles and circles show the results when the metal layer was provided during the heat treatment, and the squares and the squares show the case where the metal layer was not provided during the heat treatment. From this, it is understood that the carrier concentration is increased and the p-type conductivity is promoted by providing the metal layer and performing the heat treatment. This is because the metal layer draws hydrogen from the p-type GaN layer 5 during the heat treatment to cause a reduction reaction, which promotes the reduction of the resistance of the p-type GaN layer 5. Also, among the results of providing the metal layer, the circles are
The results of heat treatment performed in O 2 atmosphere are shown, and the ● marks show the results of heat treatment performed in N 2 atmosphere. However, heat treatment performed in O 2 atmosphere has a higher carrier concentration than that performed in N 2 atmosphere. Is high, that is, p-type conversion is promoted. A carrier concentration of about 1 × 10 17 / cm 3 was obtained by heat treatment at about 550 ° C in an O 2 atmosphere, and about 1 × 10 14 / cm 3 at a heat treatment of about 500 ° C.
Carrier concentration can be obtained. This is because p-type GaN is produced by the above-mentioned redox reaction by heat treatment in an O 2 atmosphere.
This is because the reduction of resistance of the p-type GaN layer 5 is promoted by the continuous redox reaction by drawing out hydrogen from the layer 5.
Therefore, by using an O 2 atmosphere, it is possible to obtain the highest carrier concentration of 1 × 10 18 / cm 3 by heat treatment at about 650 ° C. On the other hand, in other cases, further high temperature conditions were required, and the carrier concentration did not reach the carrier concentration when the heat treatment was performed in the O 2 atmosphere after forming the metal layer.

【００２０】図４は、図２のサンプル２０を用いて、熱
処理温度と導電率との関係を示した特性図である。図中
の○印、●印及び■印は、図３と同じ条件で得られた結
果を示している。図３と同様な図４に示す特性が得られ
た。即ち、金属層が、熱処理時にｐ型GaN 層５から水素
を引き抜いて還元反応を生じるためにｐ型GaN 層５の低
抵抗化が促進されるので、金属層を設けない場合より、
金属層を設けた場合の方が高い導電率が得られる。又、
O2雰囲気中で熱処理することにより、還元された金属が
熱処理時に再び酸化されてｐ型GaN 層５から水素を引き
抜いて還元反応を生じるために、ｐ型GaN 層５の低抵抗
化が促進されるので、N2雰囲気中で熱処理を行う場合よ
りさらに高い導電率が得られる。図４より、約 1×10-2
/ Ωcm以上の高い導電率を得るには、O2雰囲気を用いれ
ば約550 ℃で熱処理すればよく、約650 ℃で熱処理すれ
ば最も高い導電率に達する。以上のことから、約600 ℃
以上の温度、望ましくは650 ℃で熱処理することで低抵
抗ｐ型半導体が得られることがわかる。FIG. 4 is a characteristic diagram showing the relationship between the heat treatment temperature and the conductivity using the sample 20 of FIG. In the figure, ○, ● and ■ indicate the results obtained under the same conditions as in FIG. The characteristics shown in FIG. 4 similar to FIG. 3 were obtained. That is, since the metal layer draws hydrogen from the p-type GaN layer 5 during the heat treatment to cause a reduction reaction, lowering the resistance of the p-type GaN layer 5 is promoted.
Higher conductivity is obtained when the metal layer is provided. or,
By performing the heat treatment in the O 2 atmosphere, the reduced metal is oxidized again during the heat treatment and hydrogen is extracted from the p-type GaN layer 5 to cause a reduction reaction, so that the resistance reduction of the p-type GaN layer 5 is promoted. Therefore, higher conductivity can be obtained as compared with the case of performing heat treatment in N 2 atmosphere. From Figure 4, about 1 × 10 -2
In order to obtain a high conductivity of / Ωcm or more, heat treatment at about 550 ° C may be used in an O 2 atmosphere, and heat treatment at about 650 ° C may reach the highest conductivity. From the above, about 600 ℃
It can be seen that a low resistance p-type semiconductor can be obtained by heat treatment at the above temperature, preferably 650 ° C.

【００２１】上記図３及び図４は、金属層をCoで構成し
たときの特性を示したものであるが、他のCo，Au，Ni，
Cu，Pd，Mn等の単層構造又はこれらの積層構造を用いた
場合も同様であった。これは、ｐ型GaN 層５上に前述の
各種の金属層を設けて熱処理することで、ｐ型GaN 層５
中の水素が金属層に吸着されるので、低抵抗化が促進さ
れるためである。さらに、O2雰囲気中で熱処理すること
で、金属層が酸化され、その酸化された金属層がさらに
水素を吸着してGaN 層５の低抵抗化を促進するので、金
属層に酸化性金属を用いれば効果的である。3 and 4 show the characteristics when the metal layer is composed of Co, other Co, Au, Ni,
The same was true when a single layer structure of Cu, Pd, Mn or the like or a laminated structure of these was used. This is performed by providing the above-mentioned various metal layers on the p-type GaN layer 5 and heat-treating them.
This is because the hydrogen inside is adsorbed by the metal layer, which promotes the reduction of resistance. Furthermore, the heat treatment in an O 2 atmosphere oxidizes the metal layer, and the oxidized metal layer further adsorbs hydrogen and promotes the reduction in resistance of the GaN layer 5. It is effective when used.

【００２２】上記実施例では、ｐ電極６の形成後の熱処
理において、10PaのO2ガス雰囲気を用いたが、O2ガスの
圧力はこれ以上であっても十分な効果を発揮する。又、
ｐ電極６の形成後の熱処理において、N2ガスに対して１
％のO2ガスを含ませ、そのO2ガスの分圧を１００Paとし
た雰囲気中での熱処理を行ったが同様な効果が得られ
た。このように、純粋な酸素ガスの他、O2にN2,He,Ne,A
r,Krのうちの１種以上を加えたガスが利用可能であり、
圧力及びO2の分圧は、上述した圧力範囲で全て利用可能
である。In the above embodiment, an O 2 gas atmosphere of 10 Pa was used in the heat treatment after the formation of the p-electrode 6, but a sufficient effect is exhibited even if the O 2 gas pressure is higher than this. or,
In the heat treatment after the formation of the p-electrode 6, 1 against N 2 gas
% O 2 gas was added and the heat treatment was performed in an atmosphere in which the partial pressure of the O 2 gas was 100 Pa, but the same effect was obtained. Thus, other pure oxygen gas, N 2 in O 2, He, Ne, A
Gases containing one or more of r and Kr are available,
The pressure and the partial pressure of O 2 are all available in the pressure range mentioned above.

【００２３】又、GaN 層５を低抵抗化するための金属層
の厚さは、5 〜3000Åであることが望ましい。金属層の
厚さが５Åより薄いと水素の引き抜き効果が弱くなり、
300Åより厚いとｐ層、金属層界面にO2が供給されにく
くなるからである。又、上記実施例では、発光素子１０
の発光層４はＭＱＷ構造としたが、ＳＱＷやGa0.08In
0.92N 等から成る単層、その他、任意の混晶比の４元、
３元系のAlGaInN としても良い。又、ｐ型不純物として
Mgを用いたがベリリウム(Be)、亜鉛(Zn)等の２族元素を
用いることができる。本発明は従来の透光性の金属電極
を用いる場合はもちろん、フリップチップタイプのよう
に厚い電極を用いる場合にも適用できる。又、本発明は
ＬＥＤやＬＤの発光素子に利用可能であると共に受光素
子にも利用することができる。本実施例では、ｐ型GaN
層５を低抵抗化した後、金属層９を除去したが、この金
属層９を除去することなく、例えば、金属層９と同一金
属やオーミック性が得られる異種金属等を積層して透明
電極を構成しても良い。また、金属層９を除去すること
なく、オーミック性が得られる同種又は異種の金属から
成るフリップチップタイプの厚い金属電極を形成しても
良い。The thickness of the metal layer for reducing the resistance of the GaN layer 5 is preferably 5 to 3000Å. If the thickness of the metal layer is less than 5Å, the hydrogen extraction effect becomes weaker,
This is because if it is thicker than 300Å, it becomes difficult to supply O 2 to the interface between the p layer and the metal layer. In the above embodiment, the light emitting element 10
The light emitting layer 4 of has an MQW structure, but SQW and Ga 0.08 In
Single layer consisting of 0.92 N, etc., other quaternary with arbitrary mixed crystal ratio,
It may be ternary AlGaInN. Also, as p-type impurities
Although Mg is used, a Group 2 element such as beryllium (Be) or zinc (Zn) can be used. The present invention can be applied not only to the case of using a conventional translucent metal electrode but also to the case of using a thick electrode such as a flip chip type. Further, the present invention can be used not only for light emitting elements such as LEDs and LDs but also for light receiving elements. In this example, p-type GaN
After the resistance of the layer 5 was reduced, the metal layer 9 was removed. However, without removing the metal layer 9, for example, the same metal as the metal layer 9 or a dissimilar metal capable of obtaining ohmic properties is laminated to form a transparent electrode. May be configured. Further, it is possible to form a flip chip type thick metal electrode made of the same kind or different kinds of metals that can obtain ohmic properties without removing the metal layer 9.

【図面の簡単な説明】[Brief description of drawings]

【図１】本発明の具体的な実施例に係わるGaN 系化合物
半導体素子の構造を示した模式的断面図。FIG. 1 is a schematic cross-sectional view showing the structure of a GaN-based compound semiconductor device according to a specific example of the present invention.

【図２】本発明の具体的な実施例に係わるGaN 系化合物
半導体素子の特性を測定するために用いられたサンプル
の構成を示した模式的斜視図。FIG. 2 is a schematic perspective view showing the structure of a sample used for measuring the characteristics of a GaN-based compound semiconductor device according to a specific example of the invention.

【図３】キャリア濃度と熱処理温度との関係を示した特
性図。FIG. 3 is a characteristic diagram showing the relationship between carrier concentration and heat treatment temperature.

【図４】導電率と熱処理温度との関係を示した特性図。FIG. 4 is a characteristic diagram showing the relationship between conductivity and heat treatment temperature.

【符号の説明】[Explanation of symbols]

１ サファイア基板 ２ バッファ層 ３ ｎ型GaN 層 ４ 発光層 ５ ｐ型GaN 層 ６ ｐ電極 ７ 電極パッド ８ ｎ電極 ９ 金属層 １０ 発光素子 ４１ バリア層 ４２ 井戸層 ６１ 第１金属層 ６２ 第２金属層 1 sapphire substrate 2 buffer layers 3 n-type GaN layer 4 Light emitting layer 5 p-type GaN layer 6 p electrode 7 electrode pad 8 n electrode 9 metal layers 10 Light emitting element 41 Barrier layer 42 well formation 61 first metal layer 62 second metal layer

───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平９−64337（ＪＰ，Ａ) 特開 平９−129919（ＪＰ，Ａ) 特開 平８−51235（ＪＰ，Ａ) 特開 平９−191129（ＪＰ，Ａ) 特開 平６−188455（ＪＰ，Ａ) 特開 平10−135515（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) H01L 33/00 H01L 29/43 H01S 5/00 - 5/50 H01L 21/205 ─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-9-64337 (JP, A) JP-A-9-129919 (JP, A) JP-A-8-51235 (JP, A) JP-A-9- 191129 (JP, A) JP-A-6-188455 (JP, A) JP-A-10-135515 (JP, A) (58) Fields investigated (Int.Cl. 7 , DB name) H01L 33/00 H01L 29 / 43 H01S 5/00-5/50 H01L 21/205

Claims (4)

(57)【特許請求の範囲】(57) [Claims] 【請求項１】 ｐ型の窒化ガリウム系化合物半導体を製
造する方法において、 アクセプタ不純物の添加された窒化ガリウム系化合物半
導体の表面に金属から成る薄膜を形成した後、熱処理を
することで低抵抗ｐ型半導体を得て、 前記熱処理の後に、前記薄膜を除去した後に電極を形成
すること を特徴とする窒化ガリウム系化合物半導体の製
造方法。1. A method for producing a p-type gallium nitride compound semiconductor, which comprises forming a metal thin film on the surface of a gallium nitride compound semiconductor to which an acceptor impurity has been added, and then subjecting it to heat treatment to obtain a low resistance p Type semiconductor is obtained , and after the heat treatment, electrodes are formed after removing the thin film
A method for producing a gallium nitride-based compound semiconductor, comprising: 【請求項２】 前記熱処理は、少なくとも酸素(O) を含
む雰囲気中で行われることを特徴とする請求項１に記載
の窒化ガリウム系化合物半導体の製造方法。2. The method for producing a gallium nitride-based compound semiconductor according to claim 1, wherein the heat treatment is performed in an atmosphere containing at least oxygen (O). 【請求項３】 前記金属は、コバルト(Co)、ニッケル(N
i)、アルミニウム(Al)、銅(Cu)、パラジウム(Pd)、マン
ガン(Mn)、バナジウム(V) 及び金(Au)のうち少なくとも
１種より成ることを特徴とする請求項１又は２に記載の
窒化ガリウム系化合物半導体の製造方法。3. The metal is cobalt (Co), nickel (N)
i), aluminum (Al), copper (Cu), palladium (Pd), manganese (Mn), vanadium (V) and gold (Au), and at least one of them is characterized by the above-mentioned. A method for producing the gallium nitride-based compound semiconductor described. 【請求項４】 前記薄膜は、5 〜3000Åの膜厚に形成さ
れたことを特徴とする請求項１乃至３のいずれか１項に
記載の窒化ガリウム系化合物半導体の製造方法。4. The method of manufacturing a gallium nitride-based compound semiconductor according to claim 1, wherein the thin film is formed to have a film thickness of 5 to 3000 Å.
JP33094497A 1997-11-13 1997-11-13 Method of manufacturing gallium nitride based compound semiconductor Expired - Fee Related JP3509514B2 (en)

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