Determination of Piezoelectric Fields Across InGaN/GaN Quantum Wells by Means of Electron Holography

Electron holography was used to determine the piezoelectric fields across an InGaN/GaN quantum-well structure. Holograms were taken with the sample intentionally tilted such that adjacent layers overlapped. The phase changes in the overlapping regions were analyzed to determine the piezoelectric fields in each well. It was shown that the piezoelectric field was strongest at the central part of the quantum-well structure. The field strength averaged over eight InGaN wells was ~2.2 MV/cm.     

LP—MOCVD生长InGaN及InGaN／GaN量子阱的研究

利用MOCVD系统在Al2O3衬底上生长InGaN材料和InGaN/GaN量子阱结构材料，研究发现InGaN材料中In组份几乎不受TMG与TMI的流量比的影响，而只与生长温度有关，生长温度由800℃降低到740℃，In组份的从0.22增加到0.45；室温InGaN光致发光光谱（PL）峰全半高宽（FWHM）为15.5nm;InGaN/GaN量子阱区InGaN的厚度2nm，但光荧光的强度与100nm厚InGaN的体材料相当。     

Investigation into the Distribution of Built-in Electric Fields in LED Heterostructures with Multiple GaN/InGaN Quantum Wells by Electroreflectance Spectroscopy

Semiconductors - Electric-field nonuniformity in the active region of a LED (light-emitting diode) heterostructure based on five identical GaN/InGaN quantum wells is investigated by the...     

Luminescence Line Broadening Caused by Alloy Disorder in InGaN Quantum Wells

Semiconductors - The broadening of the spectral linewidth of the GaN/InGaN/GaN quantum wells caused by the random distribution of indium and gallium atoms in the cation sublattice was analyzed...     

预应变InGaN/GaN多量子阱发光特性调控研究

为了减弱InGaN/GaN量子阱内的压电极化场,在蓝紫光InGaN/GaN多量子阱激光器结构中采用了预应变InGaN插入层,通过变温电致发光和高分辨X射线衍射测量研究了预应变插入层对量子阱晶体质量和发光特性的影响。实验结果显示,常温下有预应变层的量子阱电致发光谱积分强度显著提高。模拟计算进一步表明,预应变层对量子阱内压电极化场有调制效果,有利于量子阱中的应力弛豫,可以有效减弱量子限制斯塔克效应,有助于提高量子阱的发光效率。     

纳米柱InGaN/GaN多量子阱的干法刻蚀制备技术

纳米柱GaN基多量子阱(MQW)拥有量子尺寸效应以及应变释放等特性,对于提高GaN基发光二极管(LED)的发光效率具有重要意义.采用快速热退火(RTA)形成的自组装Ni纳米颗粒作为刻蚀掩膜,利用电感耦合等离子体反应离子刻蚀(ICP-RIE)制备纳米柱InGaN/GaN MQW.通过改变RTA温度发现在800℃以上才能有效形成Ni纳米颗粒掩膜.不同的ICP和射频(RF)功率条件下制备的纳米柱MQW光致发光强度相比于相同结构的平面MQW会发生显著变化.通过优化ICP-RIE的刻蚀条件,可以获得发光强度显著提高的纳米柱MQW结构.同时,纳米柱MQW中压电极化场的减弱会形成光致发光峰位蓝移.     

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.     

Study of the Parameters of a Two-Dimensional Electron Gas in InGaN/GaN Quantum Wells by Terahertz Plasmon Resonance

Semiconductors - A new approach to determining the parameters of a two-dimensional electron gas (2DEG) in InGaN/GaN quantum wells is proposed. It is based on terahertz time-domain...     

Effect of Deep Centers on Charge-Carrier Confinement in InGaN/GaN Quantum Wells and on LED Efficiency

Semiconductors - The deep-center-assisted tunneling of carriers in p–n structures of light-emitting diodes (LEDs) with InGaN/GaN quantum wells (QWs) makes smaller the effective height of the...     

高反射率电极及n-GaN表面粗化的InGaN/GaN多量子阱LED的研制

采用高反射率的Cr/Al/Pd/Au作为LED的p-GaN和n-GaN金属电极,替代低反射率的Cr/Pd/Au电极,减小了金属电极对光的吸收,使入射到高反射率金属电极的光经过反射后增加了出射概率,提高了光萃取效率.通过进一步粗化n-GaN表面,抑制了n-GaN/空气界面的光全反射,提高了光萃取效率.实验结果表明,在350 mA电流下,采用高反射率的Cr/Al/Pd/Au电极的LED相比传统电极LED光输出增加了14.3％;结合n-GaN表面粗化,LED的光输出则增加了35.3％.     

Reduced Recovery Time Semiconductor Optical Amplifier Using p-Type-Doped Multiple Quantum Wells

The effect of p-type doping of the active region of multiple quantum-well (MQW) semiconductor optical amplifiers (SOAs) has been studied. Spectrogram measurements of the dynamics of the SOAs reveal that using p-doped barriers for the MQWs has significantly reduced both gain and phase recovery times. 1/e phase recovery times as short as 11 ps were demonstrated using this approach     

GaAs (110)量子阱的电子自旋弛豫

采用固态源分子束外延的方法在GaAs(110)取向衬底上生长了GaAs/AlGaAs多量子阱结构.对样品进行了低温光致发光谱和时间分辨光致发光谱的测量,结果表明激发功率和激发波长对室温下量子阱内电子的自旋弛豫时间有强烈的影响.对于常见的GaAs(100)量子阱起支配作用的D'yakonov-Perel' (DP)自旋弛豫机制,在GaAs (110)量子阱材料里被充分地抑制了.对于缺失了DP相互作用的GaAs (110)多量子阱,电子-空穴相互作用对自旋弛豫时间随激发功率变化有重要的影响.     

GaAs (110)量子阱的电子自旋弛豫

采用固态源分子束外延的方法在GaAs(110)取向衬底上生长了GaAs/AlGaAs多量子阱结构.对样品进行了低温光致发光谱和时间分辨光致发光谱的测量,结果表明激发功率和激发波长对室温下量子阱内电子的自旋弛豫时间有强烈的影响.对于常见的GaAs(100)量子阱起支配作用的D'yakonov-Perel' (DP)自旋弛豫机制,在GaAs (110)量子阱材料里被充分地抑制了.对于缺失了DP相互作用的GaAs (110)多量子阱,电子-空穴相互作用对自旋弛豫时间随激发功率变化有重要的影响.     

Influence of Mg Doping on the Morphological, Optical, and Structural Properties of InGaN/GaN Multiple Quantum Wells

In this report, the influence of magnesium doping on the characteristics of InGaN/GaN multiple quantum wells (MQWs) was investigated by means of atomic force microscopy (AFM), photoluminescence (PL), and X-ray diffraction (XRD). Five-period InGaN/GaN MQWs with different magnesium doping levels were grown by metalorganic chemical vapor deposition. The AFM measurements indicated that magnesium doping led to a smoother surface morphology. The V-defect density was observed to decrease with increasing magnesium doping concentration from ∼10⁹ cm⁻² (no doping) to ∼10⁶ cm⁻² (Cp₂Mg: 0.04 sccm) and further to 0 (Cp₂ Mg: 0.2 sccm). The PL measurements showed that magnesium doping resulted in stronger emission, which can be attributed to the screening of the polarization-induced band bending. XRD revealed that magnesium doping had no measurable effect on the indium composition and growth rate of the MQWs. These results suggest that magnesium doping in MQWs might improve the optical properties of GaN photonic devices.     

GaN{11-22}半极性面上生长InGaN/GaN多量子阱的研究

利用选择性横向外延技术生长{11-22}半极性面GaN模板,并利用半极性面模板生长InGaN/GaN多量子阱结构。结果表明,生长出的GaN模板由半极性面{11-22}面和c面组成,多量子阱具有390nm和420 nm的双峰发光特性,局域阴极发光(CL)测试表明390 nm附近的发光峰来源于半极性面上的量子阱发光,而420 nm左右的发光峰源于c面量子阱发光。c面量子阱发光相对于斜面量子阱发光发生显著红移是因为在选择性横向外延生长过程中,In组分相比Ga较易从掩模区域向窗口中心区域迁移,形成了中心高In组分的c面量子阱,而半极性面上InGaN/GaN多量子阱量子限制斯塔克效应相比于极性面会减弱,此外,相同生长条件下半极性面的生长速率低于极性c面的生长速率。     

不同形状量子阱的量子限制效应

采用差分法求解有效质量方程，考虑轻重空穴的混合效应及应变效应，对三种不同形状的量子阱的能带结构、价带态密度、跃迁矩阵元进行了比较。在阱宽相同的条件下，方阱有最大的限制能力，但抛物阱和三角阱有更平坦的态密度曲线，使得以抛物阱和三角阱为有源区的激光器和半导体激光放大器可以有较低的透明电流密度。同时价带子带的耦合强烈改变了跃迁矩阵元，这对量子阱的增益特性会产生影响。     

InGaN基蓝色发光二极管量子阱阻挡层的优化设计

计算比对了不同垒层构型量子阱的极化电场,对极化场下能级结构、载流子浓度分布、自发辐射复合速率和缺陷所造成的Shockley-Reao-Hall(SRH)非辐射复合速率进行了研究,确定内建电场引起的量子阱区域载流子浓度分布均匀性是影响器件效能高低的关键因素.对大电流下晶格优化的A10.02In0.1Ga0.88N四元材料作为量子阱垒层的器件效能和发光特性下降的原因进行了深入分析,同时提出了具体的解决方法.     

压力下屏蔽对有限深量子阱中施主结合能的影响

考虑电子有效质量、材料介电常数及禁带宽度随流体静压力的变化,以及准二维电子气对杂质库仑势的屏蔽影响,利用变分法讨论有限深量子阱中的施主杂质态能级.对GaAs/AlxGa1-xAs量子阱系统中的杂质态结合能进行了数值计算,给出结合能随铝组分、阱宽和压力的变化关系,并讨论了有无屏蔽时的区别.结果表明,屏蔽效应随着压力增加而增加且显著降低杂质态的结合能.     

压力下屏蔽对有限深量子阱中施主结合能的影响

考虑电子有效质量、材料介电常数及禁带宽度随流体静压力的变化,以及准二维电子气对杂质库仑势的屏蔽影响,利用变分法讨论有限深量子阱中的施主杂质态能级.对GaAs/AlxGa1-xAs量子阱系统中的杂质态结合能进行了数值计算,给出结合能随铝组分、阱宽和压力的变化关系,并讨论了有无屏蔽时的区别.结果表明,屏蔽效应随着压力增加而增加且显著降低杂质态的结合能.