Quantum capture dynamics between different semiconductor quantum structures

为了探究在不同阱厚度的电子隔离半导体量子阱中，光生载流子的竞争性量子捕获过程与晶格温度的关系，研究了光致发光（PL）发射动力学，得到了以下结果：在由3个或4个不同大小的量子阱组成的量子阱样品中进行了微秒级时间分辨的量子阱实验。实验发现，与热平衡条件下预期的PL强度分布相反，低能量发射带的PL强度比高能量发射带弱得多。在几个样品中观察到的独特的PL特征反映了量子捕获过程和动力学表现，例如，PL寿命比辐射重组寿命短得多。温度对量子捕获动力学的影响实验表明，量子阱之间光激发载流子的竞争捕获引起的PL复合动力学表现出与已知的二维激子辐射复合寿命完全不同的温度效应。利用生长中断分子束外延技术制备了具有单层生长岛梯田的GaAs复合量子阱，研究了阱宽波动对量子捕获动力学的影响。通过对PL结果的详细分析，新发现PL强度分布和动力学都受到第一激发子带态与势垒带边缘的相对能量位置的显著影响。此外，还证实了激子在岛台之间的传递过程。复合量子阱系统中量子捕获动力学机制通过比较两种相似但外层包层不同的复合量子阱样品（AlGaAs合金和GaAs/AlAs超晶格数字合金），发现其PL强度分布和动力学（包括温度依赖性）都有很大的不同。这些结果表明，量子捕获过程背后的机制对包层的子带能量结构很敏感，光生载流子从包层分布到具有不同子带能量结构的不同阱中。少

In order to pursue mechanisms behind the competitive quantum capture processes of photogenerated carriers as a function of lattice temperature in electronically isolated semiconductor quantum wells with different well thicknesses, photoluminescence (PL) emission dynamics have been investigated and following results are obtained.1. Existence of quantum capture processes in PL emission spectraPicosecond time-resolved PL experiments have been undertaken in quantum well samples consisting of three or four different size wells. It is experimentally found that the lower energy emission bands show much weaker PL intensities than the higher energy ones, as opposed to the PL intensity distribution expected in thermal equilibrium conditions. The unique PL characteristics observed in several samples reflect the quantum capture processes and the dynamics exhibit, for example, much shorter PL lifetimes than the radiative recombination lifetimes.2. Temperature effects on quantum capture dynamicsIt i … More s experimentally demonstrated that the PL recombination dynamics originating from the observed competitive capture of photoexcited carriers between the quantum wells exhibit totally different temperature effects from the ones already known for the radiative recombination lifetimes of two dimensional excitons.3. Dependence of well width fluctuations on quantum capture dynamicsQuantum capture dynamics have been studied in composite GaAs quantum wells with monolayer growth island terraces, prepared by growth-interrupted molecular beam epitaxy. From detailed analysis of the PL results, it is newly discovered that the PL intensity distribution as well as the dynamics are both significantly influenced by relative energy positions of the first excited subband state to the barrier band edge. In addition, the transfer proceeses of excitons are confirmed between the island terraces.4. Mechanisms of quantum capture dynamics in composite quantum well systemsFrom comparison between two similar composite quantum well samples but with different configurations of outer clad layers (AlGaAs alloy and GaAs/AlAs superlattice digital alloy), it is found that both the PL intensity distribution and the dynamics including the temperature dependence are very different each other. These results suggest that mechanisms behind the quantum capture processes are sensitive to the subband energy structures of the clad layers, from which photogenerated carriers are distributed to the different wells with different subband energy structures. Less