CN201749864U

CN201749864U - GaN base light emitting diode (LED) with higher electrostatic breakdown voltage

Info

Publication number: CN201749864U
Application number: CN2010201672380U
Authority: CN
Inventors: 吴德华; 朱学亮; 曲爽; 李树强; 徐现刚
Original assignee: Shandong Huaguang Optoelectronics Co Ltd
Current assignee: Shandong Huaguang Optoelectronics Co Ltd
Priority date: 2010-04-23
Filing date: 2010-04-23
Publication date: 2011-02-16
Anticipated expiration: 2020-04-23

Abstract

The utility model provides a GaN base light emitting diode (LED) with higher electrostatic breakdown voltage, which structurally and sequentially comprises a SiC or Si underlay, an AlN buffering layer, an N type GaN layer, an MQW layer and a P type GaN layer from bottom to top, wherein an AlGaN insertion layer with the thickness between 20nm and 100nm is arranged in the N type GaN layer. The utility model directly inserts an AlGaN on the SiC and Si underlay during the N type GaN layer growth through changing the underlay materials and the LED growth structure, the breakdown voltage of an LED chip can be fundamentally enhanced, because the NGaN layer per se is very thick, only TMA1 needs to be introduced during the AlGaN layer insertion, the growth can be easily realized, the reverse antistatic capability is improved from 500V to 1000V of an ordinary structure to 2000V to 4000V, the reverse breakdown voltage is improved from the original 15V to 30V, and the brightness is improved from 50 to 80mcd to 80 to 100mcd.

Description

GaN base LED with higher electrostatic breakdown voltage

Technical field

The utility model relates to a kind of GaN base LED (light-emitting diode) with higher electrostatic breakdown voltage, belongs to the photoelectron technology field.

Background technology

With GaN is the III-nitride (AlN, GaN, InN, AlGaInN) of representative owing to have good photoelectric characteristic, thereby is used widely in blue light, green glow, ultraviolet light-emitting diode (LED) and high frequency, high temperature high power electronic device.Owing to lack the substrate of lattice match, III-nitride all is that heteroepitaxy is on other materials, substrate commonly used has sapphire, SiC (carborundum), Si (silicon), GaAs, zinc oxide etc., and epitaxy method commonly used has metal-organic chemical vapor deposition equipment (MOCVD), molecular beam epitaxy (MBE) and hydride gas-phase epitaxy (HVPE) etc.

And SiC (carborundum) is a wide bandgap semiconductor materials, compares with Si, and it has many advantages in application.Owing to have the band gap of broad, the working temperature of SiC device can be up to 600 ℃, and the thermal conductivity of SiC is 4.5W/cmK, and the thermal conductivity of Si is 1.5W/cmK, and sapphire thermal conductivity is 0.5W/cmK.From this, the thermal conductivity of SiC and Si is outstanding with respect to sapphire, and especially on high power device, SiC and Si have wide prospect more.The hot operation ability of SiC device has reduced the requirement to system's heat budget.In addition, the SiC device also has high thermal, high breakdown field strength, high saturation drift velocity, high thermal stability and chemical inertness, and its breakdown field strength is than similar Si device height.Comprehensively relatively see, compare with Sapphire Substrate, the LED material of SiC and the growth of Si substrate, heat conductivility is outstanding.

GaN based light-emitting diode Smalt, green, the blue-green diode of producing all adopts Sapphire Substrate at present, the chip that uses the MOCVD technology to produce.The characteristics of this kind chip are: good brightness, technology are ripe relatively, and patent dispute or conflict are less relatively.So most in the world chip producers (comprising TaiWan, China, Korea S, Japanese most of manufacturers) adopt this kind technology to produce blue, green glow chip (have only except the U.S. CREE, adopt the SiC substrate).The shortcoming of this kind chip is that antistatic effect is relatively poor, as if being subjected to electrostatic impact, can cause Vf (forward voltage drop) to raise, and brightness reduces with the lamp phenomenon that causes death, so how to prevent static, is topmost problem in indigo plant, green light-emitting diode production and the use.

Based on the LED of PN junction structure, in manufacturing, screening, test, packing, accumulating and link such as install and use, not influenced by electrostatic induction and produce charge inducing.If can not get timely release, the high voltage that forms on two electrodes of LED will directly add the PN junction two ends of led chip.After voltage surpasses the maximum bearing value of LED, electrostatic charge will discharge between two electrodes of led chip with extremely short moment (nanosecond rank), the heat of power joule will make the conductive layer of led chip inside, the part of PN luminescent layer form high temperature, high temperature will be melt into aperture to these layers, thereby causes the phenomenon of electric leakage and short circuit.

The performance that static wounds: chip is subjected to static and wounds, and can form black splotch on its surface, and this black splotch will can be not luminous again, so, the degree difference that chip is wounded, its performance is also different.Slight wounds, and perhaps do not come out outwardly, but the brightness meeting reduces brightness meeting decay, IR value (reverse current) rising on a small quantity; The chip that moderate is wounded, its tube voltage drop can obviously raise (may be increased to more than 4.0V～5.5V), and brightness obviously reduces (below 50% of former normal brightness), IR raises, have a strong impact on the life-span, in use can lose function gradually, also may cause dead lamp at last.So, present indigo plant, green light-emitting diode must be carried out anti-static precautions, and make regular check on earth resistance in the process of producing and using, and like this, just can avoid dead lamp phenomenon significantly.

The GaN material of led chip is a wide-band gap material, and resistivity is higher, and uses sapphire as substrate, this backing material is non-conductive, such chip is difficult for disappearing because of the induced charge of generation of static electricity in process of production, is accumulated to suitable degree, can produce very high electrostatic potential.When surpassing the ability to bear of material, punch-through and discharge can take place.Its positive and negative electrode of the blue chip of Sapphire Substrate all is positioned at above the chip, and spacing is very little; For the InGaN/GaN multi-quantum pit structure, the InGaN active layer is tens nanometers only, and is very little to the ability to bear of static, very easily by electrostatic breakdown, makes component failure.GaN base LED compares with traditional LED, and the antistatic effect difference is its distinct shortcoming, and the Problem of Failure that static causes has become influences very stubborn problem of product percent of pass and use popularization one.

Indigo plant, the present antistatic effect level of green luminous tube: antistatic effect has only about 50V, oppositely will cause immediately dying more than the static 500V.Forward static also can cause major injury immediately more than 1500V, and in northern winter, the static of human body is greatly about about 1000V-1500V, so it is the main cause that causes the diode damage that human body directly contacts diode.In any production, use in the process of diode, all want strictness to forbid that human body directly contacts diode at no anti-static precautions.

In present safeguard procedures, diode production all adopts the certified products diode chip for backlight unit, (dustless, all process steps antistatic) produces diode under the working condition of strictness, and production standard (IR leak electricity standard) is strict controlled in 5V, the standard of 10 μ A, industry standard 5V, 50 μ A " in the overall process of producing, detect, packing, all realize automation; avoid artificial factor influence fully, guaranteed product quality.But these all can only be made an issue of from outward appearance and protection aspect, can not solve substantial problem.

The structure of existing Sapphire Substrate GaN based light-emitting diode comprises Sapphire Substrate 5, AlN resilient coating 4, N type GaN layer 3, MQW (Multiple Quantum Well) layer 2 and P type GaN layer 1 as shown in Figure 1 from bottom to top.Chinese patent literature CN101359710A discloses " a kind of manufacture method of green light LED ", this method is by add the insert layer of InAlGaN in the MQW of growing InGaN and GaN (quantum well), reduce the V defective between InGaN and the GaN, reduce separating out of In component, obtain green LED high brightness, that antistatic effect is strong.The advantage of this technology is the increase by insert layer, and brightness is increased to 250mcd from 100mcd, and electrostatic breakdown voltage is increased to 4000V from 500V.But the substrate that this technology is used is sapphire.Will insert InAlGaN, AlGaN, InGaN or InAlN layer in mqw layer, this layer thickness is 0.1-5nm, and mqw layer itself is thinner, control Al and In growth on the growth technique simultaneously, to when growth, introduce very difficulty of operation, probably destroy MQW, cause not luminous.

Summary of the invention

The utility model provides the GaN base LED with higher electrostatic breakdown voltage that a kind of preparation technology is simple, be easy to realize at the deficiency that the electrostatic breakdown voltage that has Sapphire Substrate GaN light-emitting diode now develops skill and exists.

GaN base LED with higher electrostatic breakdown voltage of the present utility model, its structure comprises SiC or Si substrate, AlN resilient coating, N type GaN layer, MQW (Multiple Quantum Well) layer and P type GaN layer from bottom to top successively, is provided with the AlGaN insert layer that a layer thickness is 20nm-100nm in the N type GaN layer.

Above-mentioned is to insert one deck AlGaN to improve electrostatic breakdown voltage in N type GaN layer with SiC or Si as the structure of substrate growing GaN base LED.Because polarity effect causes that positive bound charge is arranged at the interface, this AlGaN layer bound charge can be induced and be formed a two-dimensional electron gas at the heterojunction boundary place.This two-dimensional electron gas transverse conductance ability is strong, is beneficial to current expansion; When pulse current is added in LED, by two-dimensional electron gas electric current is evenly expanded, avoid local current too high, reduce the destruction of reverse impulse to LED.

The utility model is by changing the growth structure of backing material and LED, directly when growing N type GaN layer, inserting one deck AlGaN on SiC, the Si substrate, voltage is worn in the resistance that fundamentally strengthens light-emitting diode chip for backlight unit, because NGaN layer itself is thicker, only need introduce TMAl (trimethyl aluminium) when inserting the AlGaN layer, growth is very easy to realize that oppositely antistatic effect has been brought up to 2000V-4000V by the 500V-1000V of ordinary construction.Reverse breakdown voltage is brought up to 30V by original 15V.Brightness has been brought up to 80-100mcd by 50-80mcd, and aging decay in 168 hours has also been brought up to 5%-10% by original 20%-30%.

Description of drawings

Fig. 1 is the structural representation of existing Sapphire Substrate GaN based light-emitting diode.

Fig. 2 is the structural representation that the utlity model has the GaN base LED of higher electrostatic breakdown voltage.

Among the figure: 1, P type GaN layer, 2, MQW (Multiple Quantum Well) layer, 3, N type GaN layer, 4, the AlN resilient coating, 5, Sapphire Substrate, 6, the AlGaN insert layer, 7, SiC or Si substrate.

Embodiment

As shown in Figure 2, GaN base LED with higher electrostatic breakdown voltage of the present utility model, its structure comprises SiC or Si substrate 7, AlN resilient coating 4, N type GaN layer 3, AlGaN insert layer 6, N type GaN layer 3 from bottom to top successively, MQW (Multiple Quantum Well) layer 2 and P type GaN layer 1.Its preparation method is to adopt the growth of MOCVD (metal organic-matter chemical gaseous phase deposition) method, inserts one deck AlGaN when growth N type GaN layer, and all the other processes are the same with existing conventional technology of preparing, specifically may further comprise the steps:

(1) at 1000 ℃-1100 ℃, NH ₃Flow is the growth of carrying out AlN resilient coating 4 under the condition of 1L/ minute-3L/ minute on SiC or Si substrate 7, and growth thickness is that 20nm-100nm obtains even curface.This step is with existing the same according to a conventional method.

(2) at 950 ℃-1100 ℃ thick N type GaN layers 3 of growth 1um, this step is with existing the same according to a conventional method.

(3) treat that growing GaN when thick, introduces TMAl (trimethyl aluminium) to 1um, source is originally introduced constant, and temperature is reduced to 900 ℃-1050 ℃ growth AlGaN insert layers 6 down by 950 ℃-1100 ℃ then, and thickness is 20nm-100nm.

(4) at 950 ℃-1100 ℃ thick N type GaN layers 3 of growth 0.1um-0.5um.This step is with existing the same according to a conventional method.

(5) at 600 ℃-900 ℃ thick mqw layers 2 of growth 80nm-200nm.This step is with existing the same according to a conventional method.

(6) at 700 ℃-1000 ℃ thick P type GaN layers 1 of growth 150nm-300nm.This step is with existing the same according to a conventional method.

By the LED of the method growth, oppositely antistatic effect has been brought up to 2000V-4000V by the 500V-1000V of ordinary construction, and reverse breakdown voltage is brought up to 30V by original 15V.And brightness has also improved 1/3rd.Because use SiC or Si as substrate, heat-sinking capability is strong, and conductive capability is good, and tube core technology is simple, more importantly is to have solved problem of aging, makes light-emitting diode have the longer life-span.

Claims

1. GaN base LED with higher electrostatic breakdown voltage, its structure comprises SiC or Si substrate, AlN resilient coating, N type GaN layer, mqw layer and P type GaN layer from bottom to top successively, it is characterized in that: be provided with the AlGaN insert layer that a layer thickness is 20nm-100nm in the N type GaN layer.