摘要
小兔和狼GaN基LED凭借其可控的全色光谱能隙以及优良的物理化学性能，在各种照明、背光等领域有着广泛的应用前景，已逐步成为新一代绿色照明光源。目前LED照明的主流技术方案是“蓝光LED+黄色荧光粉”合成白光，虽然可以获得较高的光效，但色温、显色指数等色品质不佳。为了获得真正意义上的高品质LED照明光源，白光需要采用全LED混光来实现，即采用红、绿、蓝三基色LED （RGB）获得白光，这样就可以实现低色温、高显色指数以及高效率的完美结合。而目前绿光的发光效率远远落后于蓝光和红光LED，学术界称之为“Green gap”，这也成为实现RGB白光光源的主要技术瓶颈。因此，进一步提升绿光LED量子效率成为近几年LED领域的研究热点。与垒之间的晶格失配导致量子阱中存在较大应力，这种应力对绿光LED的光电性能有明显影响，但一直没有统一的认知。基于硅衬底LED技术平台，本文通过改变垒结构较为系统地研究了垒对硅衬底绿光LED应力、光电特性、结温特性以及老化特性的影响。获得了以下研究成果：
1）采用高分辨率X射线衍射（HRXRD）测试了三种不同垒结构（垒中含InGaN、垒含AlGaN以及全GaN垒）的Si衬底GaN基绿光LED外延薄膜（1015）面非对称衍射倒易空间分布图，定性的表征了三种结构量子阱的应力状态，结果表明，垒层中引入InGaN和AlGaN均能明显减小绿光量子阱所受的压应力，其中引入InGaN时所受压应力最小。
2）将上述三种垒结构的Si衬底GaN基绿光LED外延片制作成垂直结构芯片，研究了其变温电致发光（VTEL）性能，结果表明：在同一温度下，随着电流密度的增加，三种结构的EL峰值波长均发生蓝移，但程度存在差异。环境温度为低温13K时，随着电流密度的增加，垒中含AlGaN的蓝移量大于全GaN垒，全GaN垒和垒中含InGaN的蓝移量相近。在环境温度为300K（室温）时，蓝移量的大小也不同，大小关系为：全GaN垒大于垒中含AlGaN，垒中含AlGaN又大于垒中含InGaN。波长的蓝移量与量子限制斯塔克效应（QCSE）引起的能带弯曲量有关，蓝移量越小则能带弯曲越小。由此可见，相比全GaN垒，垒中引入AlGaN和InGaN能够有效减小QCSE，尤其是垒中引入InGaN。这与前述三种垒结构引起的绿光量子阱中应力大小关系完全吻合。
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3）对以上三种结构的绿光LED芯片在常温、500mA下老化500小时后，三种垒结构的器件光衰均比较小，全GaN垒为2.47%，垒中含AlGaN为5.33%，垒中含InGaN为3.56%，三种结构光衰的大小不同可能与结构不同导致的量子阱内部应力大小不同有关。开启电压和工作电压变化很小，最大差值分别在0.01V 和0.1V左右。
4）对三种垒结构的垂直结构绿光LED芯片结温进行了研究，通过对从小到大一系列电流下结温系数的测定得出：小电流下结温系数偏差很大，其原因是芯片内存在漏电通道，小电流测试时器件漏电流占
测试电流比重大，对结温系数影响大；大电流结温系数偏差小，原因为大电流测试时漏电流达到饱和，并且占测试电流比重非常小。基于以上判断，建立了正确测试绿光LED芯片结温的方法。并通过此方法表征了三种垒结构绿光LED芯片结温温升特性，结果显示：垒中含InGaN的绿光LED结温温升最小，其次是全GaN垒结构，而垒中含AlGaN的样品的结温温升值最大。
5）通过对垒结构为全GaN的Si衬底GaN基绿光LED外部应力的控制，研究分析了EL光谱随应力的变化规律，结果表明：在退火过程中Si衬底GaN基绿光LED 薄膜GaN受到的张应力逐渐减小，量子阱受到的压应力则逐渐增大，由此导致压电效应增加，量子阱的量子限制斯达克效应（QCSE）加剧，导致随着外部应力变小，光功率下降，半峰宽加大和波长增大等现象。此结果再此证明，减小绿光量子阱中所受的压应力有利于提升其光电特性。
6）综上可知，减小绿光量子阱所受的压应力有利于提升其光电性能，通过在垒中引入InGaN和AlGaN可以有效减小绿光量子阱所受的压应力。综合来看，垒中引入InGaN的绿光LED结构性能最佳，主要表现为量子阱所受应力最小，室温下随电流密度增大蓝移量最小，结温温升最小，老化过程中光电参数稳定。以上研究结果为进一步提升绿光LED光电性能具有一定了实验和理论价值。传说中的勇者传说
关键词：硅衬底；绿光LED；量子阱；应力；光电性能
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Abstract
Abstract
工程投标书LED bad on GaN,with its controllable panchromatic spectrum as well as excellent physical and chemical properties,has broad application prospects in a variety of areas such as lighting,backlighting and has gradually become the new generation of green illumination photosource.The current the mainstream technology program of LED illumination is the"blue LED+yellow phosphor"synthetic white LED,although you can get a higher luminous efficiency,isochromatic quality such as the color warm and the colored index is not good.In order to obtain a high-quality LED lighting in the true n,white light requires a full LED mixed light,namely the u of red,green,blue three primary color LED（RGB）to obtain white light,so that you can achieve the perfect combination of low color temperature,high color rendering index as well as high efficiency.At prent,the luminous efficiency of green light LED is far behind the blue and red LED,it is called"Green gap"in the academic circles,which has become a main technical bottlenecks to achieve RGB white light sources.Therefore,further advancing the green light LED quantum efficiency becomes a hot topic the field of LED in recent years.The large lattice mismatch between the barrier and well in the quantum well will cau large stress,which has obvious effects on optical and electric
花生的谜语怎么说al properties of the Green light LED,but there has been no unified cognition.This article study barrier structure’s of silicon substrate green light LED effects on many characteristics such as stress, optical and electrical properties,the junction temperature characteristics and aging characteristics.The following rearch results:
1）Using high-resolution x-ray diffraction（HRXRD），test reciprocal space mapping with（1015）face non-symmetric diffraction of three different barrier structures（barrier including InGaN,barrier including AlGaN,the full GaN barrier）green LED epitaxial film of GaN-bad on Si substrate.Characterize qualitatively the stress state of three quantum well structure,the results showed that the introduction of
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Abstract
InGaN and AlGaN barrier layer can obviously reduce the tensile stress in quantum well of green LED,in which when introducing InGaN the tensile stress is smallest.
2)The three barrier structures of green LED epitaxial films of GaN-bad on Si substrate wafer into t
花椰菜英文he chips with the vertical structure and study the variable temperature electroluminescence properties（VTEL）,the results show that:At the same temperature,with the increa of current density,EL peak wavelength of three kinds of structure are the blue shifting,but they are different in degree.when the ambient temperature is low temperature-13K,with increasing current density,there is a bigger amount of blue shift ing including AlGaN in barrier than the entire GaN barrier, the quantity of blue shifting is similar between the entire GaN barrier and barriers including InGaN.When the environment temperature is300k（room temperature）, the quantity of blue shifting is also different,the relations are:the entire GaN barrier is bigger than barrier containing AlGaN,barrier containing AlGaN is bigger than barrier containing InGaN.The quantity of wavelength in blue shift is related to the band bending caud by the quantum confined Stark effect（QCSE）,the quantity of blue shift is smaller,the band bending is smaller.Thus,compared to the entire GaN barrier,the introduction of AlGaN and InGaN in the barrier can effectively reduce the QCSE,especially the introduction of InGaN barrier.It is consistent fully with the above stress relationship caud three different barrier structures in quantum wells of the green light LED.
3)On the above three kinds of green light LED chips with different structure under room temperature,500mA aging for500hours,the light attenuation of three kinds of devices with different th
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e barrier structures is relatively small,the entire GaN barrier to2.47%,the barrier containing AlGaN to5.33%,the barrier containing InGaN to3.56%,their light attenuation may differ from the structure of quantum wells resulting from internal stress is different.The variation of turn-on voltage and the operating voltage is small;the maximum difference is respectively about0.01V and0.1V.
月工作总结怎么写4)The junction temperature of three kinds of the green LED chips with the vertical structure and different barrier structures was studied,through a ries
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Abstract
measurement of temperature coefficients under the different currents from small to large,The conclusions obtained:The deviation of coefficient of temperature under the low current is larger,its reason is that there are the leakage channels in the chips, under low current,the ratio of leakage current occupying the test current is significant,this make a major impact on the junction temperature coefficient;The deviation of coefficient of temperature under the large current is smaller,the reason is, the leakage current is saturated for the large current test and accounts for a very small proportion of the test current.Bad on the above judgment,the correct way to test junction temperature of green L
ED chips has been t up.Further,through this method characterize junction temperature rising characteristics of three kinds of barrier structures of green light LED chips,the results showed:It is smallest including InGaN in barriers of green light LED,the fllowing is the entire GaN barrier and the next is including AlGaN in barriers.
5)Through controlling external stress of green light LED of GaN-bad on Si substrate,study and analyze variations of d the EL Spectra with the strain,the results show that:In the annealing process,the tensile stress of GaN decreas gradually for green LED epitaxial films of GaN-bad on Si substrate,compressive stress of quantum wells increas,which leds to the increasing of piezoelectric effect in quantum well and quantum limit Stark effect（QCSE）,some phenomenons such as that chip parameters with the external stress becomes small,light power is down,half peak width increas and wavelength increas.This further certifies that decreasing the tensile stress of green light quantum well is helpful to improve the photoelectric properties.
6)In conclusion,reducing tensile stress of quantum well with green light LED is beneficial to improve the photoelectric performance,and introducing InGaN and AlGaN in barrier can effectively reduce the tensile stress in green light quantum.All in all,InGaN introduced the green LED structure has best performance,mainly the stress is smallest in quantum well,the amount of blue shifting is smallest wit
h increasing current density at room temperature and has the minimum junction temperature rising,stable photoelectric parameters in the process of aging.The above
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