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Properties Of Non-polar A-plane Gan/algan Quantum Wells

机译:非极性A平面Gan / Algan量子阱的性质

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The structural and optical properties of a series of GaN/Al_(0.18)Ga_(0.82)N multiple quantum well (MQW) structures, in which the well thickness was varied between 2 and 8 nm, grown on a-plane (1120) GaN on r-plane (1102) sapphire substrates have been investigated. High-resolution X-ray diffraction and low-angle X-ray reflectivity measurements were used to determine the well and barrier thicknesses and the barrier composition after matrix transformation of the (binary) elastic constants for the appropriate coordinates, and assuming a pseudo-morphically strained system. The microstructure of the (1120) samples is dominated by I_1-type basal-plane stacking faults (BSF) terminated by partial dislocations or prismatic stacking faults, as determined by conventional and high-resolution transmission electron microscopy. The low temperature photoluminescence (PL) spectra of the QW structures show two emission bands which are assigned (partly based on photoluminescence excitation (PLE) spectroscopy) to excitons that are confined solely by the quantum wells and, at lower energy, those carriers that recombine in the region where the wells are intersected by BSFs. Both bands shift to higher energy with decreasing quantum well thickness. The optical data indicate that the non-polar (1120) GaN/AlGaN system is free of polarization-induced electric fields, since the QW exciton emission energy is not below the band-edge emission energy of the GaN template.
机译:在a平面(1120)GaN上生长的一系列GaN / Al_(0.18)Ga_(0.82)N多量子阱(MQW)结构的结构和光学性质,其中阱厚度在2到8 nm之间变化在r平面(1102)上的蓝宝石衬底已得到研究。高分辨率X射线衍射和低角度X射线反射率测量用于在适当坐标的(二进制)弹性常数进行矩阵变换后确定阱和势垒厚度以及势垒组成,并假设其为拟态紧张的系统。 (1120)样品的微观结构主要由I_1型基面堆叠断层(BSF)所主导,该断层以部分位错或棱柱状堆叠断层终止,这是由常规和高分辨率透射电子显微镜确定的。 QW结构的低温光致发光(PL)光谱显示了两个发射带,这两个发射带被分配给(部分基于光致发光激发(PLE)光谱)激子,激子仅由量子阱限制,而在较低能量下,这些载流子重新结合在井与BSF相交的区域中。随着量子阱厚度的减小,两个带都转移到更高的能量。光学数据表明,非极性(1120)GaN / AlGaN系统没有极化感应电场,因为QW激子发射能不低于GaN模板的带边发射能。

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