N型掺杂ZnSe/BeTe Ⅱ型量子阱中空间间接带电激子跃迁发光的直接证据

摘要/Abstract

摘要： 本文研究了N型掺杂ZnSe/BeTe/ZnSe Ⅱ型量子阱空间间接发光谱的外加电场依赖性。实验结果表明,其发光谱只显示了一个线性偏振度较低的发光峰。这是由于掺杂电子屏蔽了Ⅱ型量子阱中的内秉电场,并使得两个ZnSe阱层具有相同的势。同时该发光谱具有反玻耳兹曼(inverse-Boltzmann)分布,并且线型和线性偏振度在整个栅极电压变化范围内没有显示明显改变。然而,其光谱积分强度却显著地依赖栅极电压的极性变化:在正栅极电压范围内(7~0 V)其光谱积分强度几乎是一个常数,但随着负栅极电压的增加(-1~-7 V),其光谱积分强度却显著降低。这些行为显示了该样品的空间间接发光谱具有负的带电激子的特征。这个常数的光谱积分强度被解释为掺杂层对外加电场的屏蔽,而这个显著降低的光谱积分强度则被归因于外加电场对掺杂电子的排斥(致使激光激发区域内的电子浓度降低),从而导致了负带电激子数量的减少。此外,本文也初步探讨了该空间间接带电激子的可能构成模型。

关键词: 光致发光, 带电激子, 量子阱, 电场, N型掺杂ZnSe/BeTe, 线性偏振度

Abstract: Applied electric field dependence of spatially indirect luminescence spectra of N-doped ZnSe/BeTe/ZnSe type-Ⅱ quantum wells was studied. Experimental results indicate that each of the luminescence spectra exhibits a main luminescence peak with a lower linear polarization degree. This phenomenon can be attributed to the equalizing potential of both wells, which is due to the screening of the built-in electric field caused by the doped electrons in the structure. Meanwhile, each of the luminescence spectra exhibits an asymmetry peak with an inverse-Boltzmann line-shape, and the line-shape and linear polarization degree remain unchanged within the entire voltage range. However, the integrated luminescence intensity depends strikingly on various external voltages: with changing the positive gate voltage (in the range of +7 V to 0 V), the integrated luminescence intensity almost maintains a constant, but with increasing negative gate voltage (-1 V to -7 V), the integrated luminescence intensity reduces significantly. These behaviors indicate that the spatially indirect luminescence spectra show a characteristic feature for a negatively charged exciton transition. The constant integrated luminescence intensity is explained as screening of the applied electric field with the doped layer, while the significantly reduced integrated luminescence intensity is ascribed to excitation of doping electrons by applied electric field (leading to a decrease in the electron concentration in the region excited by laser), thus resulting in a reduction in the number of negatively charged exciton. In addition, the possible particle configuration of the spatially indirect negatively charged exciton was also explored.

Key words: photoluminescence, charged exciton, quantum well, electric field, N-doped ZnSe/BeTe, linear polarization degree

中图分类号:

O471.3

屈尚达, 冀子武. N型掺杂ZnSe/BeTe Ⅱ型量子阱中空间间接带电激子跃迁发光的直接证据[J]. 人工晶体学报, 2021, 50(2): 290-295.

QU Shangda, JI Ziwu. Direct Evidence of Spatially Indirect Charged Exciton Transition Photoluminescence in N-doped ZnSe/BeTe Type-Ⅱ Quantum Wells[J]. JOURNAL OF SYNTHETIC CRYSTALS, 2021, 50(2): 290-295.

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