AlGaN /GaN分布布拉格反射镜的MOCVD生长

文中利用MOCVD方法,采用高质量GaN作为缓冲层,在（0001）取向的蓝宝石衬底上实现了不同组分的AlxGa1-xN/GaN分布布拉格反射镜（DBR）的制备.通过XRD、SEM、AFM、反射谱等测量分析手段,研究了AlxGa1-xN/GaN DBR的结构质量、厚度和表面形貌.     

AlGaN /GaN分布布拉格反射镜的MOCVD生长

文中利用MOCVD方法,采用高质量GaN作为缓冲层,在(0001)取向的蓝宝石衬底上实现了不同组分的Alx Ga1 - xN /GaN分布布拉格反射镜(DBR)的制备。通过XRD、SEM．AFM、反射谱等测量分析手段,研究了Alx Ga1 - xN /GaN DBR的结构质量、厚度和表面形貌。     

DBR单纵模光纤激光器波长温度调谐

报道了采用DBR方式,利用8 mm的高浓度掺Yb3+单模光纤,实现了波长为1 064 nm的单纵模调谐激光稳定输出的实验结果。该DBR谐振腔有效腔长为16 mm,输出最大功率为7.4 mW,通过半导体制冷器温控改变谐振腔的温度,实现了0.824 nm的单纵模无跳模调谐。采用光纤外差法,并利用低损耗环形器和光纤反射镜倍增延迟线长度提升测量精度的方式,测量得到激光最大线宽为4.4 kHz。单纵模激光的弛豫震荡峰位于900 kHz处,其相对强度噪声为-110 dB/Hz,当频率大于1.5 MHz时相对强度噪声为-145 dB/Hz。     

DBR掺铒光纤激光器的功率特性研究

本文主要研究DBR掺铒光纤激光器的功率特性.通过对光纤Bragg光栅的光谱特性和激光器的传播方程的分析,得到了阈值泵浦光功率、掺铒光纤长度、Bragg光栅反射率与激光器输出光功率之间的关系.与近期报道的实验数据进行了比较,结果十分吻合.     

MOCVD外延生长GaN材料的技术进展

第三代半导体材料GaN由于具有优良性质使其在微电子和光电子领域有广阔的应用前景,目前制备GaN的方法主要有分子束(MBE)、氯化物气相外延(HVPE)、金属有机物化学气相沉积(MOCVD)。其中HVPE技术制备GaN的速度最快,适合制备衬底材料;MBE技术制备GaN的速度最慢;而MOCVD制备速度适中。因而MOCVD在外延生长GaN材料方面得到广泛应用。介绍了MOCVD法外延生长GaN材料的基本理论、发展概况、利用MOCVD法外延生长GaN材料的技术进展。认为应结合相关技术发展大面积、高质量GaN衬底的制备技术,不断完善缓冲层技术,改进和发展横向外延技术,加快我国具有国际先进水平的MOCVD设备的研发速度,逐步打破进口设备的垄断。     

间歇供氨高温AlN缓冲层对AlGaN/GaN异质结的影响

研究了以间歇供氨的方法直接高温生长的氮化铝为缓冲层的AlGaN/GaN材料,高温氮化铝的应用可以有效的提高晶体质量和表面形貌,并且二维电子气的浓度和迁移率也得到改善。     

采用多级变速法生长AlGaAs电流扩展层的850nm红外发光二极管

对采用多级变速法生长AlGaAs电流扩展层的850nm红外发光二极管进行了研究。研究发现,采用多级变速法生长n型Al0.25Ga0.75As电流扩展层有助于改善外延层表面形貌和后续外延层的晶体质量,从而减小850nm红外发光二极管的漏电流及串联电阻。此外,采用多级变速法生长n型Al0.25Ga0.75As电流扩展层还可以避免在多量子阱(MQW)有源区中形成非辐射复合中心,从而提高850nm红外发光二极管的亮度和寿命。     

AlGaN缓冲层结构对Si基GaN材料性能的影响

Si衬底与GaN之间较大的晶格失配和热失配引起的张应力使GaN外延层极易产生裂纹,如何补偿GaN所受到的张应力是进行Si基GaN外延生长面临的首要问题.采用金属有机化合物化学气相沉积(MOCVD)技术在4英寸(1英寸=2.54 cm)Si (111)衬底上制备了GaN外延材料并研究了不同AlGaN缓冲层结构对Si基GaN外延材料性能的影响,并采用高分辨X射线衍射仪(HRXRD)、原子力显微镜(AFM)、喇曼光谱以及光学显微镜对制备的GaN材料的性能进行了表征.采用3层A1GaN缓冲层结构制备了表面光亮、无裂纹的GaN外延材料,其(002)晶面半高宽为428 arcsec,表面粗糙度为0.194 nm.结果表明,采用3层A1GaN缓冲层结构可以有效地降低GaN材料的张应力和位错密度,进而遏制表面裂纹的出现,提高晶体质量.     

具有渐变式折射率分布布拉格反射层的发光二极管

对具有渐变式折射率分布布拉格反射层(GRIN-DBR)的发光二极管进行了研究。研究发现,在传统分布布拉格反射层(C-DBR)的AlAs/Al0.45Ga0.55As的界面处插入5nm厚的折射率渐变层,可以使DBR的反射带宽从82nm增加到103nm。在20mA注入电流下,具有GRIN-DBR的发光二极管与具有C-DBR的发光二极管的正向电压没有明显区别,而其光通量比具有C-DBR的发光二极管高8%。     

InGaN/GaN多量子阱蓝光LED的p-GaN盖层的MOCVD生长研究

利用金属有机物化学气相淀积（MOCVD）生长了InGaN／GaN多量子阱（MQW）蓝光发光二极管（LED）,研究了不同Cp2Mg流量下生长的p-GaN盖层对器件电学特性的影响。结果表明,随着Cp2Mg流量的提高,漏电流升高,并且到达一临界点会迅速恶化;正向压降则先降低,后升高。进而研究相同生长条件下生长的p-GaN薄膜的电学特性、表面形貌及晶体质量,结果表明,生长p-GaN盖层时,Cp2Mg流量过低,盖层的空穴浓度低,电学特性不好;Cp2Mg流量过高,则会产生大量的缺陷,盖层晶体质量与表面形貌变差,使得空穴浓度降低,电学特性变差。因此,生长p-GaN盖层时,为使器件的正向压降与反向漏电流均达到要求,Cp2Mg流量应精确控制。     

In situ growth monitoring of AlGaN/GaN distributed Bragg reflectors at 530 nm using a 633 nm laser

The metal-organic chemical vapor deposition(MOCVD) growth of AlGaN/GaN distributed Bragg reflectors (DBR) with a reflection peak at 530 nm was in situ monitored using 633 nm laser reflectometry.Evolutions of in situ reflected reflectivity for different kinds of AlGaN/GaN DBR were simulated by the classical transfer matrix method.Two DBR samples,which have the same parameters as the simulated structures,were grown by MOCVD.The simulated and experimental results show that it is possible to evaluate the DBR...     

MOCVD生长高反射率AlN/GaN分布布拉格反射镜

利用金属有机物化学气相沉积(MOCVD)方法在蓝宝石c面衬底上制备出高反射率AlN/GaN分布布拉格反射镜(DBR).利用分光光度计测量,在418 nm附近最大反射率达到99%.样品表面显微照片显示,有圆弧形缺陷和少量裂纹出现;在缺陷和裂纹以外的区域,DBR具有较为平坦的表面,其粗糙度在10μm×10μm面积上为3.3 m左右.样品的截面扫描电镜(SEM)照片显示,DBR具有良好的周期性.对反射率和表面分析的结果表明,该样品达到了制备GaN基垂直腔面发射激光器(VCSEL)的要求.     

Efficiency enhancement of InGaN/GaN light-emitting diodes with a back-surface distributed bragg reflector

The design, fabrication, and performance characteristics of a back-surface distributed Bragg reflector (DBR) enhanced InGaN/GaN light-emitting diode (LED) are described. A wide reflectance bandwidth in the blue and green wavelength regions is obtained using a double quarter-wave stack design composed of TiO₂ and SiO₂ layers. More than 65% enhancement in extracted light intensity is demonstrated for a blue LED measured at the chip level. Similar improvement in green LED performance is discussed and achieved through simulation. Possible applications of back-surface DBR-enhanced LEDs include surface-mount packages with significantly reduced vertical profiles, resonant cavity LEDs, and superluminescent diodes.     

GaN 基蓝光发光二极管分布布拉格反射器的设计

采用传输矩阵法对GaN基蓝光发光二极管分布布拉格反射器(DBR)反射光谱进行研究.计算发现正入射时S偏振(TE模)与P偏振(TM模)反射带是一致的; S偏振和P偏振反射带随着入射角的增大都向高频(短波)方向移动,且两者之间的差别也随之增大,DBR反射带蓝移快慢与入射介质相关;低折射率入射介质时DBR具有更宽角度响应.通过修改结构参数多次计算表明;入射角修正的方法能较快地找到提高全方向反射的结构.复合DBR以降低反射率或者成倍增加膜层厚度为代价实现大角度范围的反射,复合DBR比传统DBR有更好的光谱特性,这对提高发光二极管的出光效率有现实意义.     

GaN基蓝光发光二极管分布布拉格反射器设计研究

采用传输矩阵法对GaN基蓝光发光二极管分布布拉格反射器（DBR）反射光谱进行研究。计算发现正入射时S偏振(TE模)与P偏振(TM模)反射带是一致的;S偏振和P偏振反射带随着入射角的增大都向高频(短波)方向移动,且两者之间的差别也随之增大,DBR反射带蓝移快慢与入射介质相关;低折射率入射介质时DBR具有更宽角度响应。通过修改结构参数多次计算表明：入射角修正的方法能较快的找到提高全方向反射的结构。复合DBR以降低反射率或者成倍增加膜层厚度为代价实现大角度范围的反射。复合DBR比传统DBR有更好的光谱特性,这对提高发光二极管的出光效率有现实意义。     

Frequency and wavelength tunable optical microwave source based on a distributed Bragg reflector self-pulsation laser

A frequency and wavelength tunable self-pulsation laser based on DBR laser devices is reported for the first time.This laser generates continuous tunable optical microwave in the range of 1.87-21.81 GHz with 3-dB linewidth about 10 MHz by tuning the injection currents on the front and back gain sections,and exhibits wavelength tuning range from 1536.28 to 1538.73 nm by tuning the injection currents on the grating section.     

基于DBR结构自脉动激光器的波长及频率可变光微波源

首次报道了基于DBR结构自脉动激光器的波长及频率可变光微波源。该微波源可以或得1.87GHz至21.81GHz的微波信号同时可以获得1536.28nm至1538.73nm的波长调谐。     

锥形图形衬底上氮化镓薄膜生长和表征

GaN films are grown on cone-shaped patterned sapphire substrates(CPSSs)by metal-organic chemical vapor deposition,and the influence of the temperature during the middle stage of GaN growth on the threading dislocation(TD)density of GaN is investigated.High-resolution X-ray diffraction(XRD)and cathodeluminescence(CL)wereusedtocharacterizetheGaNfilms.TheXRDresultsshowedthattheedge-typedislocation density of GaN grown on CPSS is remarkably reduced compared to that of GaN grown on conventional sapphire substrates(CSSs).Furthermore,whenthegrowthtemperatureinthemiddlestageofGaNgrownonCPSSdecreases,the full width at half maximum of the asymmetry(102)plane of GaN is reduced.This reduction is attributed to the enhancement of vertical growth in the middle stage with a more triangular-like shape and the bending of TDs.The CL intensity spatial mapping results also showed the superior optical properties of GaN grown on CPSS to those of GaN on CSS,and that the density of dark spots of GaN grown on CPSS induced by nonradiative recombination is reduced when the growth temperature in the middle stage decreases.     

Sunlight-like white organic light-emitting diodes with inorganic/organic nanolaminate distributed Bragg reflector (DBR) anode microcavity by using atomic layer deposition

White organic light-emitting diodes (WOLED) with inorganic/organic/hybrid nanolaminate distributed Bragg reflector (DBR) prepared by atomic layer deposition (ALD) has been firstly developed, and the improved structural, optical, and electrical properties have been observed. The functional layer consists of periodically alternating layers of ZrO₂/Zircone (zirconium alkoxides with carbon-containing backbones) films fabricated using ALD. By well adjusting the thickness and emissive dyes of the emission layer, three white light diodes were realized based on three cavity modes with different resonance wavelength and intensity. The narrowed lectroluminescent (EL) spectra from the microcavity organic light emitting diodes (MOLEDs) are of high-purity, and the off-resonant optical mode is highly suppressed due to the excellent optical properties of the DBR layers with high reflectivity in a wide stop-band range. The CIE chromaticity coordinates of devices are tuned from (0.33, 0.34), (0.43, 0.40) to (0.57, 0.40), which are all on the planckian locus, and the color temperature is adjusted from 5783 K, 3842 K to 2245 K. This work exhibits a simple and novel approach to achieve a sunlight-like WOLED by constructing the inorganic/organic nanolaminate DBR using ALD, which will be very important for healthy display and lighting.