InGaN/GaN多量子阱的变温发光特性研究

采用低压金属有机化学沉积方法制备了InGaN/GaN多量子阱.变温PL测量发现,量子阱发光强度具有良好的温度稳定性,随着温度升高(10～300K),发光强度只减小到1/3左右.分析认为,InGaN/GaN多量子阱的多峰发光结构是由多量子阱的组分及阱宽的不均匀引起的.随着温度升高,GaN带边及量子阱的光致发光均向低能方向移动,但与GaN带边不同,量子阱发光峰值变化并不与通过内插法得到的Varshni经验公式相吻合,而是与InN带边红移趋势一致,分析了导致这种现象的可能因素.还分析了量子阱发光寿命随温度升高而减小的原因.     

InGaN/GaN多量子阱电池的垒层结构优化及其光学特性调控

InGaN基量子阱作为太阳电池器件的有源区时,垒层厚度设计以及实际生长对其光学特性的影响极为重要.采用金属有机化学气相沉积(MOVCD)技术,在蓝宝石衬底上外延生长了垒层厚度较厚的InGaN/GaN多量子阱,使用高分辨X射线衍射和变温光致发光谱研究了垒层厚度对InGaN多量子阱太阳电池结构的界面质量、量子限制效应及其光学特性的影响.较厚垒层的InGaN/GaN多量子阱的周期重复性和界面品质较好,这可能与垒层较薄时对量子阱的生长影响有关.同时,厚垒层InGaN/GaN多量子阱的光致发光光谱峰位随温度升高呈现更为明显的“S”形(红移-蓝移-红移)变化,表现出更强的局域化程度和更高的内量子效率.     

InGaN/GaN多量子阱太阳电池的研制及特性研究

利用金属有机物化学气相沉积技术在蓝宝石衬底上生长了InGaN/GaN多量子阱外延结构,高分辨率X射线衍射测量结果显示,量子阱结构界面清晰,周期重复性很好,InGaN阱层的In组分约为0.2。利用该外延结构制备的InGaN/GaN多量子阱太阳电池的开路电压为2.16V,转换效率达到了0.64%。器件的I-V测量结果显示,在光照条件下,曲线的正向区域存在一明显的"拐点"。随着聚光度的减小,I-V曲线的"拐点"逐渐向高电压区域移动,同时器件的开路电压也随之急剧下降。通过与理论计算对比,发现器件开路电压的下降幅度明显大于理论计算值。进一步分析表明,InGaN量子阱的极化效应不仅是I-V曲线产生拐点以及器件开路电压下降过快的主要原因,也是影响氮化物太阳电池性能的关键因素之一。     

InGaN/GaN和InGaN/AlGaN多量子阱中应变对光致发光特性的影响

对蓝宝石衬底上的InGaN/GaN和InGaN/AlGaN多量子阱结构和经激光剥离去除衬底的InGaN/GaN和InGaN/AlGaN多量子阱结构薄膜样品,进行了光致发光谱、高分辨XRD和喇曼光谱测量.PL测量结果表明,相对于带有蓝宝石衬底的样品,InGaN/GaN多量子阱薄膜样品的PL谱峰值波长发生较小的蓝移,而InGaN/AlGaN多量子阱薄膜样品的PL谱峰值波长发生明显的红移;喇曼光谱的结果表明,激光剥离前后E2模的峰值从569.1减少到567.5cm-1.这说明激光剥离去除衬底使得外延层整体的压应力得到部分释放,但InGaN/GaN与InGaN/AlGaN多量子阱结构中阱层InGaN的应力发生了不同的变化.XRD的结果证实了这一结论.     

InGaN/GaN和InGaN/AlGaN多量子阱中应变对光致发光特性的影响

对蓝宝石衬底上的InGaN/GaN和InGaN/AlGaN多量子阱结构和经激光剥离去除衬底的InGaN/GaN和InGaN/AlGaN多量子阱结构薄膜样品,进行了光致发光谱、高分辨XRD和喇曼光谱测量.PL测量结果表明,相对于带有蓝宝石衬底的样品,InGaN/GaN多量子阱薄膜样品的PL谱峰值波长发生较小的蓝移,而InGaN/AlGaN多量子阱薄膜样品的PL谱峰值波长发生明显的红移;喇曼光谱的结果表明,激光剥离前后E2模的峰值从569.1减少到567.5cm-1.这说明激光剥离去除衬底使得外延层整体的压应力得到部分释放,但InGaN/GaN与InGaN/AlGaN多量子阱结构中阱层InGaN的应力发生了不同的变化.XRD的结果证实了这一结论.     

InGaN/GaN 和 InGaN/AlGaN 多量子阱中应变对光致发光特性的影响

对蓝宝石衬底上的InGaN/GaN和InGaN/AlGaN多量子阱结构和经激光剥离去除衬底的InGaN/GaN和InGaN/AlGaN多量子阱结构薄膜样品，进行了光致发光谱、高分辨XRD和喇曼光谱测量. PL测量结果表明，相对于带有蓝宝石衬底的样品，InGaN/GaN多量子阱薄膜样品的PL谱峰值波长发生较小的蓝移，而InGaN/AlGaN多量子阱薄膜样品的PL谱峰值波长发生明显的红移；喇曼光谱的结果表明，激光剥离前后E2模的峰值从569.1减少到567.5cm-1. 这说明激光剥离去除衬底使得外延层整体的压应力得到部分释放，但InGaN/GaN与InGaN/AlGaN多量子阱结构中阱层InGaN的应力发生了不同的变化. XRD的结果证实了这一结论.     

生长温度对InGaN/GaN多量子阱LED光学特性的影响

利用低压MOCVD系统,在蓝宝石衬底上外延生长了InGaN/GaN多量子阱蓝紫光LED结构材料.研究了生长温度对有源层InGaN/GaN多量子阱的合金组分、结晶品质及其发光特性的影响.结果表明当生长温度从730℃升到800℃时,LED的光致发光波长从490nm移到380nm,室温下PL谱发光峰的半高全宽从133meV降到73meV,表明了量子阱结晶性的提高.高温生长时,PL谱中还观察到了GaN的蓝带发光峰,说明量子阱对载流子的限制作用有所减弱.研究表明,通过改变生长温度可以对LED发光波长及有源层InGaN的晶体质量实现良好的控制.     

InGaN多量子阱面发射微盘激光器的理论研究

为了实现半导体微盘磁光器的单模面发射,设计了一种以ＩｎＧａＮ多量子阱为有源层,ＣａＮ外延层为覆盖层的半导体微盘激光器。通过对ＧａＮ覆盖层进行图形刻蚀,可以对不同的角模式进行有选择的增益,由此实现选模。用有效增益因子加电介质盘的模型对实际微盘结构进行简化,并根据此模型计算微盘外的远场分布,并进上步计算有效增益因子。分析表明,这种结构能够实现ｍ＝１角模式的面发射。     

阱宽和垒厚对lnGaN/GaN多量子阱结构光电特性的影响

通过求解修正的基于K·p方法的有效质量哈密顿方程并与泊松方程进行自洽,得到在极化效应影响下的不同阱宽和垒厚的InGaN/GaN多量子阱导带和价带的能带结构,并计算了不同多量子阱结构的自发辐射谱.仿真结果表明:阱宽和垒厚对InGaN/GaN多量子阱结构的光电子学特性有很大的影响.随着阱宽和垒厚的增加,InGaN/GaN多...     

低温ZnSe/ZnS多量子阱光学双稳态

我们在77K温度下,观察了ZnSe/ZnS多量子阱的激光吸收及激子带展宽现象。在不同的激发波长处进一步得到了增强吸收双稳和色散型双稳态。非线性机制为激子带展宽。     

InGaN/GaN岛形量子阱样品透射电镜制样与表征方法

本文研究了氮化物半导体三维岛形结构的透射电镜制样技术,减小了样品在制样过程中的结构损伤,并对In Ga N/Ga N量子阱进行了结构、成分和发光特性的表征。通过对三维Ga N小岛非极性小面微观结构的分析,确定了侧壁小面皆为半极性面,说明小面生长的In Ga N/Ga N量子阱受到较小的极化效应影响。该岛形量子阱的结构特征,有效地增强了量子阱的发光效率,同时由于不同小面的存在,实现了同一小岛的多波长白光发射。     

Low-Temperature photoluminescence of SiGe/Si disordered multiple quantum wells and quantum well wires

Low-temperature photoluminescence from disordered SiGe/Si quantum wells and quantum wires made from periodic quantum wells by electron beam lithography and reactive ion etching has been measured. No enhancement in luminescence is seen, compared to that in periodic quantum wells, in the disordered wells or quantum wires. New transitions are observed in the wire luminescence, including a possible no-phonon transition exhibiting a 32 meV blue shift compared to the same transition in the wells.     

GaN/AIN multiple quantum wells grown on GaN-AIN waveguide structure by metalorganic vapor-phase epitaxy

High-optical-confinement waveguide structure based on nitride semiconductors is proposed and demonstrated for the first time with metal organic vaporphase epitaxy. The waveguide structure composed of 1-μm-thick AIN cladding layer, 2-μm-thick GaN guiding layer, and 40 periods of GaN/AIN multiple quantum wells (MQWs) was grown using optimized growth conditions for each layer. For improved material quality, the two-step growth technique using low-temperature AIN and GaN nucleation layers was utilized to reduce the stress induced by lattice mismatch between each layer. The high-optical-confinement structure could therefore be grown with high quality, leading to a successful observation of inter-sub-band absorption in GaN/AIN MQWs. The inter-sub-band absorption wavelength observed in such structure is in good agreement with that of MQWs grown on GaN layer, showing that the proposed waveguide structure can be used as a standard structure for optical devices based on inter-sub-band absorption.     

Application of nano-patterned InGaN fabricated by self-assembled Ni nano-masks in green InGaN/GaN multiple quantum wells

The nano-patterned InGaN film was used in green InGaN/GaN multiple quantum wells(MQWs) structure, to relieve the unpleasantly existing mismatch between high indium content InGaN and GaN, as well as to enhance the light output. The different self-assembled nano-masks were formed on InGaN by annealing thin Ni layers of different thicknesses. Whereafter,the InGaN films were etched into nano-patterned films. Compared with the green MQWs structure grown on untreated InGaN film, which on nano-patterne...     

Cubic InGaN/GaN multi-quantum wells and AlGaN/GaN distributed Bragg reflectors for application in resonant cavity LEDs

In this contribution, we present results on the growth and characterization of c-InGaN/GaN MQWs and c-AlGaN/GaN DBRs, which may be used as building blocks of green (510 nm) resonant cavity light emitting diodes, which have a high potential as light sources for local area networks using plastic optical fibers. First, the impact of the indium and gallium flux on the growth of cubic-InGaN by plasma assisted molecular beam epitaxy has been studied. Indium is observed to incorporate into the c-GaInN films only when the gallium flux is reduced significantly below the value needed for stoichiometric c-GaN growth. A decrease of the surface roughness of the InGaN layers and an increase of their photoluminescence intensity per unit thickness at the transition from metal-flux limited to active nitrogen-limited growth is observed. High quality c-InGaN/GaN multi-quantum wells were grown with superlattice peaks clearly resolved in high resolution X-ray diffraction and a strong room temperature photoluminescence with a full width at half maximum of 240 meV. Cubic-AlGaN/GaN distributed Bragg reflectors with a maximum reflectivity of about 50% at 515 nm and a stop bandwidth of 33 nm have been realized. Enhanced 526 nm room temperature photoluminescence has been observed from a combined structure of a c-InGaN/GaN multi-quantum well and a c-AlGaN/GaN distributed Bragg reflector.     

Spin-orbit splitting dependent resonant third-order nonlinear optical susceptibility in InGaN/GaN multiple quantum wells

For the transition between valence band and conduction band, the third-order nonlinear optical susceptibility χ⁽³⁾ for degenerated four-wave mixing in In_xGa_1−xN/GaN multiple quantum wells (MQWs) has been calculated. The contributions of spin-orbit split-off energy to the resonant third-order nonlinear optical susceptibility of the modes, whose polarization is vertical to the [0 0 1] direction of the MQWs, are discussed in detail. The correlations between the peaks of χ⁽³⁾, which are due to the transitions from the spin-orbit split-off energy level to first conduction subband, and the width of the quantum well and the constituents of the semiconductor material are obtained.     

InGaN/GaN多量子阱LED电致发光谱中双峰起源的研究

研究了MOCVD生长的具有双发射峰结构的InGaN/GaN多量子阱发光二极管(LED)的结构和发光特性.在透射电子显微镜(TEM)下可以发现量子阱的宽度不一致,电致发光谱(EL)发现了位于2.45eV的绿光发光峰和2.81eV处的蓝光发光峰.随着电流密度增加,双峰的峰位没有移动,直到注入电流密度达到2×104 mA/cm2时,绿光发光峰发生蓝移,而蓝光发光峰没有变化.单色的阴极荧光谱(CL)发现绿光发射对应的发光区包括絮状区域和发光点,而蓝光发射对应的发光区仅包含絮状区域.通过以上的结果,我们认为蓝光发射基本上源于InGaN量子阱发光,而绿光发射则起源于量子阱和量子点的发光.     

InGaN/GaN多量子阱LED电致发光谱中双峰起源的研究

研究了MOCVD生长的具有双发射峰结构的InGaN/GaN多量子阱发光二极管(LED)的结构和发光特性.在透射电子显微镜(TEM)下可以发现量子阱的宽度不一致,电致发光谱(EL)发现了位于2.45eV的绿光发光峰和2.81eV处的蓝光发光峰.随着电流密度增加,双峰的峰位没有移动,直到注入电流密度达到2×104 mA/cm2时,绿光发光峰发生蓝移,而蓝光发光峰没有变化.单色的阴极荧光谱(CL)发现绿光发射对应的发光区包括絮状区域和发光点,而蓝光发射对应的发光区仅包含絮状区域.通过以上的结果,我们认为蓝光发射基本上源于InGaN量子阱发光,而绿光发射则起源于量子阱和量子点的发光.