硅襯底氮化鎵基黃光LED外延生長與器件性能研究
發(fā)布時間：2018-08-30 13:46
【摘要】：近年來， GaN基LED發(fā)展迅速，開啟了半導(dǎo)體照明的時代，使LED進(jìn)入了人們的生活，被大眾所熟悉。然而，半導(dǎo)體照明的普及還有很長的路要走。目前白光照明都是基于藍(lán)光LED激發(fā)熒光粉模式，，其效率較低、成本偏高且色品質(zhì)不足。如果不用熒光粉，僅使用不同顏色的高效LED配色形成白光，發(fā)光效率將會有較大的提升空間，照明品質(zhì)也會得到大幅改善。而實現(xiàn)配色白光照明的關(guān)鍵在于提高長波段LED的發(fā)光效率，特別是黃光LED的效率。本文選取在Si襯底上研發(fā)GaN基黃光LED，目的是從最常規(guī)的方式入手，利用現(xiàn)有成熟的設(shè)備、源料和工藝，在目前藍(lán)光和綠光的基礎(chǔ)上探索新的器件結(jié)構(gòu)和生長條件，用簡單易行的方法提高GaN基黃光LED的發(fā)光效率。 首先對黃光LED的生長工藝和外延結(jié)構(gòu)進(jìn)行了創(chuàng)新：利用AlN插入層改善GaN晶體質(zhì)量，利用AlGaN漸變緩沖層調(diào)整GaN應(yīng)力，通過升高溫度改善量子阱質(zhì)量，引入應(yīng)力準(zhǔn)備層減小量子阱的應(yīng)力，引入V型坑屏蔽位錯和釋放應(yīng)力，優(yōu)化生長條件降低C污染，成功地在Si襯底上生長出GaN黃光LED外延材料。 對外延材料的各項性質(zhì)進(jìn)行了表征：測試了XRD搖擺曲線，計算了GaN中的位錯密度；使用TEM觀察了緩沖層、量子阱和V型坑的界面，分析了位錯與界面狀態(tài)的成因；測量了GaN的晶格常數(shù)和倒易空間mapping，研究了GaN與量子阱的應(yīng)力狀態(tài)；測量并擬合了各外延層的厚度與組分。 研究了Si襯底上GaN基黃光LED的器件性能：室溫35A/cm2電流密度下，通350mA電流，器件的發(fā)光波長為566nm，電壓為3.23V，光輸出功率為72mW，對應(yīng)外量子效率高達(dá)9.4%，低電流密度下外量子效率最高達(dá)到22.2%，該結(jié)果優(yōu)于文獻(xiàn)報道水平。對比了Si襯底藍(lán)、綠、黃三種波段LED的波長飄移，提出了量化計算壓電場屏蔽和能帶填充對波長飄移影響的方法，把波長隨電流密度飄移的主要原因歸結(jié)于壓電場屏蔽。研究了GaN基黃光LED變溫變電流EL光譜，觀察到低溫大電流下3個新的子發(fā)光峰，建立了空穴泄漏模型，將其分別歸結(jié)于V型坑側(cè)壁量子阱，藍(lán)光應(yīng)力準(zhǔn)備阱、In0.04Ga0.96N/GaN超晶格等三個區(qū)域的發(fā)光。 研究了GaN基藍(lán)、綠、黃三種波段LED效率的三種droop特性，把效率隨電流密度droop的主要原因歸結(jié)于應(yīng)力引起的壓電場；把效率隨溫度droop的主要原因歸結(jié)為缺陷引起的非輻射復(fù)合；把效率隨波長droop的主要原因歸結(jié)為In組分升高引起的應(yīng)力增大與缺陷增多。從能量轉(zhuǎn)換的角度解釋了LED的效率droop的原因，即載流子與環(huán)境的能量交換(吸收或釋放能量)會延長載流子輻射復(fù)合壽命，降低發(fā)光效率。此外，還對比了AlGaInP與GaN基黃光LED的性能差異，觀察到前者發(fā)光效率與發(fā)光波長的溫度穩(wěn)定性明顯不如后者，因此，GaN基取代AlGaInP基是黃光LED發(fā)展的必然趨勢。 本論文研究結(jié)果表明，Si襯底GaN基LED不但在藍(lán)、綠光范圍內(nèi)具有很高的發(fā)光效率，而且在長波段范圍也具備很大的發(fā)展?jié)摿ΑＯ嘈旁谠诓痪玫膶�，隨著技術(shù)的進(jìn)步，GaN基黃光LED效率必定會得到大幅提升，使用高效LED配色實現(xiàn)白光照明將成為現(xiàn)實。
[Abstract]:In recent years, the rapid development of GaN-based LED has opened the era of semiconductor lighting, so that LED into people's lives, known to the public. However, the popularity of semiconductor lighting still has a long way to go. At present, white light is based on blue LED phosphor excitation mode, its efficiency is low, cost is high and color quality is insufficient. Powder, only using different colors of high-efficiency LED color matching to form white light, luminous efficiency will have a greater room for improvement, lighting quality will also be greatly improved. Starting from the most conventional way, using the existing mature equipment, raw materials and technology, we explore new device structure and growth conditions on the basis of the current blue and green light, and improve the luminous efficiency of GaN-based yellow LED by simple and feasible methods.
Firstly, the growth process and epitaxial structure of yellow LED are innovated. AlN insertion layer is used to improve the quality of GaN crystal, AlGaN gradient buffer layer is used to adjust the GaN stress, QW quality is improved by increasing temperature, stress preparation layer is introduced to reduce the stress of QW, V-shaped pit shielding dislocation and release stress are introduced to optimize the growth conditions. C yellow light LED epitaxial material was successfully grown on Si substrate by C contamination.
The properties of epitaxial materials were characterized as follows: XRD swing curves were measured and the dislocation density in GaN was calculated; the interface of buffer layer, quantum well and V-shaped hole was observed by TEM, and the causes of dislocation and interface state were analyzed; the lattice constants and reciprocal mapping of GaN were measured, and the stress states of GaN and quantum well were studied. The thickness and composition of the epitaxial layers were measured and fitted.
The device performance of GaN-based yellow LED on Si substrate was studied. At room temperature of 35A/cm2 current density, the device has 350 mA current, 566 nm wavelength, 3.23V voltage, 72mW output power, 9.4% external quantum efficiency, and 22.2% external quantum efficiency at low current density. Wavelength drift of blue, green and yellow LEDs was quantitatively calculated. The main reason of wavelength drift with current density was attributed to piezoelectric field shielding. The temperature-dependent EL spectra of GaN-based yellow LEDs were studied. Three new electron emission peaks were observed at low temperature and high current. The cavity leakage model is attributed to the luminescence of V-shaped hole side wall quantum wells, blue light stress preparation wells and In0.04Ga0.96N/GaN superlattices.
Three kinds of droop characteristics of GaN-based blue, green and yellow LED efficiencies were studied. The main reason of efficiency droop with current density was attributed to piezoelectric field caused by stress, the main reason of efficiency droop with temperature was attributed to defect-induced non-radiative recombination, and the main reason of efficiency droop with wavelength was attributed to the increase of in component. The reason for the efficiency droop of LED is explained from the point of view of energy conversion, that is, the energy exchange between carrier and environment (absorption or release of energy) can prolong the recombination life of carrier radiation and reduce the luminous efficiency. The temperature stability of wavelength is obviously lower than that of the latter, so the substitution of GaN group for AlGaInP group is the inevitable trend of yellow LED development.
The results of this paper show that GaN-based LED on Si substrate not only has high luminous efficiency in blue and green light range, but also has great development potential in Long-band range.It is believed that in the near future, with the development of technology, the efficiency of GaN-based yellow LED will be greatly improved, and the use of efficient LED color matching to achieve white light will be. Become a reality.
【學(xué)位授予單位】：南昌大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TM923.34
[Abstract]:In recent years, the rapid development of GaN-based LED has opened the era of semiconductor lighting, so that LED into people's lives, known to the public. However, the popularity of semiconductor lighting still has a long way to go. At present, white light is based on blue LED phosphor excitation mode, its efficiency is low, cost is high and color quality is insufficient. Powder, only using different colors of high-efficiency LED color matching to form white light, luminous efficiency will have a greater room for improvement, lighting quality will also be greatly improved. Starting from the most conventional way, using the existing mature equipment, raw materials and technology, we explore new device structure and growth conditions on the basis of the current blue and green light, and improve the luminous efficiency of GaN-based yellow LED by simple and feasible methods.
Firstly, the growth process and epitaxial structure of yellow LED are innovated. AlN insertion layer is used to improve the quality of GaN crystal, AlGaN gradient buffer layer is used to adjust the GaN stress, QW quality is improved by increasing temperature, stress preparation layer is introduced to reduce the stress of QW, V-shaped pit shielding dislocation and release stress are introduced to optimize the growth conditions. C yellow light LED epitaxial material was successfully grown on Si substrate by C contamination.
The properties of epitaxial materials were characterized as follows: XRD swing curves were measured and the dislocation density in GaN was calculated; the interface of buffer layer, quantum well and V-shaped hole was observed by TEM, and the causes of dislocation and interface state were analyzed; the lattice constants and reciprocal mapping of GaN were measured, and the stress states of GaN and quantum well were studied. The thickness and composition of the epitaxial layers were measured and fitted.
The device performance of GaN-based yellow LED on Si substrate was studied. At room temperature of 35A/cm2 current density, the device has 350 mA current, 566 nm wavelength, 3.23V voltage, 72mW output power, 9.4% external quantum efficiency, and 22.2% external quantum efficiency at low current density. Wavelength drift of blue, green and yellow LEDs was quantitatively calculated. The main reason of wavelength drift with current density was attributed to piezoelectric field shielding. The temperature-dependent EL spectra of GaN-based yellow LEDs were studied. Three new electron emission peaks were observed at low temperature and high current. The cavity leakage model is attributed to the luminescence of V-shaped hole side wall quantum wells, blue light stress preparation wells and In0.04Ga0.96N/GaN superlattices.
Three kinds of droop characteristics of GaN-based blue, green and yellow LED efficiencies were studied. The main reason of efficiency droop with current density was attributed to piezoelectric field caused by stress, the main reason of efficiency droop with temperature was attributed to defect-induced non-radiative recombination, and the main reason of efficiency droop with wavelength was attributed to the increase of in component. The reason for the efficiency droop of LED is explained from the point of view of energy conversion, that is, the energy exchange between carrier and environment (absorption or release of energy) can prolong the recombination life of carrier radiation and reduce the luminous efficiency. The temperature stability of wavelength is obviously lower than that of the latter, so the substitution of GaN group for AlGaInP group is the inevitable trend of yellow LED development.
The results of this paper show that GaN-based LED on Si substrate not only has high luminous efficiency in blue and green light range, but also has great development potential in Long-band range.It is believed that in the near future, with the development of technology, the efficiency of GaN-based yellow LED will be greatly improved, and the use of efficient LED color matching to achieve white light will be. Become a reality.
【學(xué)位授予單位】：南昌大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TM923.34
【參考文獻(xiàn)】
相關(guān)期刊論文 前4條
1 鄺海;劉軍林;程海英;江風(fēng)益;;轉(zhuǎn)移基板材質(zhì)對Si襯底GaN基LED芯片性能的影響[J];光學(xué)學(xué)報;2008年01期
2 梁萌;王國宏;李鴻漸;李志聰;姚然;王兵;李盼盼;李t
本文編號：2213259
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