CN201038188Y

CN201038188Y - High light extraction efficiency semi-sphere GaN based large power LED chip

Info

Publication number: CN201038188Y
Application number: CNU2007200689912U
Authority: CN
Inventors: 吴中林; 徐华斌; 陈林
Original assignee: Shanghai Polytechnic University
Current assignee: Shanghai Polytechnic University
Priority date: 2007-04-16
Filing date: 2007-04-16
Publication date: 2008-03-19
Anticipated expiration: 2017-04-16

Abstract

A half-ball GaN high-power LED chip with high light extraction efficiency is provided and comprises a sapphire or GaN underlay, a GaN membrane growing on the underlay and a lightening layer with light source in the GaN membrane. The utility model is characterized in that the underlay is a half-ball shape; both the GaN membrane growing in the underlay and the lightening layer with light source in the GaN membrane are also half-ball shapes. When the semi-diameter of the ball is small enough, light from the lightening layer with light source shoots out across the half-ball GaN surface with an angle which is always smaller than the critical angle of total reflection. Total reflection will not happen on the half ball surface so most light will shoot out through the ball surface, which improves external quantum efficiency of the chip, reduces temperature rise inside the chip and improve the performance of the chip.

Description

A kind of hemisphere GaN based high-power led chip of high light-emitting efficiency

Technical field

The utility model relates to the external quantum efficiency problem of great power LED, is specifically related to a kind of hemisphere GaN based high-power led chip with high index of refraction.

Background technology

Along with the continuous progress of semiconductor fabrication and the exploitation and the application of new material, GaN base blue LED technology is tending towards ripe, the performance that makes the employing blue-light LED chip add the white light LEDs solid light source of yellow fluorescent powder is constantly improved and is entered the practical stage, at present the luminous efficiency of commercially available watt of class large power white light LEDs rises to 751m/W at the beginning of 2007 from 301m/W in 2005, luminous efficiency is significantly improved, but with (" white light LEDs present situation and the problem " delivered referring to people such as Liu Hangren of light extraction efficiency 2001m/W in theory, " light source and illumination ", in September, 2003, the 3rd phase) compare bigger gap in addition, this mainly is the not high reason of blue-light LED chip light extraction efficiency.The luminous efficiency of great power LED comprises internal quantum efficiency and external quantum efficiency, and internal quantum efficiency is the luminous efficiency when electronics and hole-recombination in the active layer, and external quantum efficiency is light that luminescent layer the sent efficient from the chip surface outgoing.The internal quantum efficiency of great power LED is very high at present, reach more than 90%, but since this material of GaN itself refractive index ratio higher, LED light output surface for planar sheet, the critical angle of the full emission of the light that active layer sent during from the plane surface outgoing of chip is smaller, therefore total reflection takes place on the surface of chip in a big chunk of the light that active layer sent, simultaneously these light that total reflections take place constantly pass through active layer in the inside of chip and are absorbed and produce heat, have influenced the luminous efficiency of chip and the raising of overall performance like this.Formerly in the technology, in order to improve the external quantum efficiency of great power LED, employing on GaN surface by laser surface alligatoring and laser lift-off substrate (" the foundation stone one gallium nitrate based white light emitting diode of solid-state illumination light source " delivered referring to people such as Zhang Guoyi, " physics and new and high technology ", the 33rd volume, o. 11th, 2004.11) method, but these methods that improve the great power LED external quantum efficiencys all fail to solve effectively the total reflection problem on chip high-index material GaN surface.

Summary of the invention

The utility model proposes a kind of hemisphere GaN based high-power led chip of high light-emitting efficiency, its purpose is to overcome existing planar sheet high-power LED chip, owing to the not high problem of the too small external quantum efficiency that causes of the surperficial cirtical angle of total reflection.

The principle of the technology of the present invention solution is: prepare and adopt hemispheric sapphire or GaN substrate, the hemisphere GaN film of on substrate, growing, and the active illuminating layer in the middle of the GaN film, because substrate is hemispheric, so can adopt the MOCVD technology growth to go out hemispheric GaN and hemispheric active illuminating layer thereof thereon, when enough hour of the radius of ball, when the light that sends from active layer incides spherical GaN surface, because the spherical shape of exit facet, the incidence angle of the overwhelming majority of the light that active layer sent on the sphere exit facet is always less than the critical angle of total reflection, can total reflection not take place and penetrate away from this surface, thereby the external quantum efficiency that makes chip obtains to improve, simultaneously because most light that active layer sent can be from the surface taking-up of chip, reduced the degree that temperature that the chip internal active layer causes the absorption of light raises, from and can improve the performance of chip.

Concrete technical scheme of the present utility model is as follows:

A kind of hemisphere GaN based high-power led chip of high light-emitting efficiency, it comprises: sapphire or GaN substrate, Grown GaN film and the active illuminating layer in the middle of the GaN film on substrate, it is characterized in that: sapphire or GaN substrate are hemisphere, and Grown GaN film and the active illuminating layer in the middle of the GaN film are hemisphere on substrate.

Advantage of the present utility model and good effect are: because substrate is hemispheric, so can adopt the MOCVD technology growth to go out hemispheric GaN film and hemispheric active illuminating layer thereof thereon, when enough hour of the radius of ball, the light that sends from active layer when the outgoing of hemisphere GaN surface, its incidence angle is always less than the critical angle of total reflection, on this hemisphere face total reflection can not take place, overwhelming majority light can be gone out in transmission, thereby the external quantum efficiency that makes chip obtains to improve, simultaneously because most light that active layer sent can be from the surface taking-up of chip, reduced the chip internal active layer absorption of light caused the degree that chip temperature raises, from and can improve the performance of chip.

Description of drawings

Fig. 1 is the hemisphere GaN based high-power led chip structural representation of a kind of high light-emitting efficiency of the utility model.1. Sapphire Substrate, 2.GaN film, 3. active illuminating layer, the 4. light that sends of active illuminating layer, 5. outgoing beam.

Embodiment

A kind of hemisphere GaN based high-power led chip of high light-emitting efficiency, as shown in Figure 2, it comprises: sapphire or GaN substrate 1, Grown GaN film 2 and the active illuminating layer 3 in the middle of the GaN film on substrate, it is characterized in that: sapphire or GaN substrate are hemisphere, and Grown GaN film and the active illuminating layer in the middle of the GaN film are hemisphere on substrate.

Present embodiment is to be of a size of at one that the preparation radius is the hemispheric substrate 1 of 1mm on the hemispheric sapphire that 20mm * 20mm, thickness are 3mm, on this substrate, adopt the hemisphere GaN film 2 of method growth LED of MOCVD and active illuminating layer 3 wherein then, and prepare electrode, behind the direct current that is connected with constant current, the light 4 that active illuminating layer 3 is sent is on inciding the hemisphere face surface time, the incidence angle of outgoing beam 5 is less than the critical angle of total reflection, can total reflection not take place and penetrates away from this cross section.

The utility model adopts the GaN based LED chip of great power of growth hemisphere exiting surface on hemisphere sapphire or GaN substrate, allow the critical angle of the incidence angle of light on spherical exiting surface that active illuminating layer sent less than total reflection, overcome technology planar sheet high-power LED chip formerly, the phenomenon that external quantum efficiency is lower, greatly improved the external quantum efficiency of high-power GaN base LED, i.e. light extraction efficiency.

Claims

1. the hemisphere GaN based high-power led chip of a high light-emitting efficiency, it comprises: sapphire or GaN substrate (1), Grown GaN film (2) and the active illuminating layer (3) in the middle of the GaN film on substrate, it is characterized in that: sapphire or GaN substrate (1) are hemisphere, and Grown GaN film (2) and the active illuminating layer (3) in the middle of the GaN film are hemisphere on substrate.