GaAs/AlAs量子阱中受主束缚能和光致发光

从实验和理论上,研究了量子限制效应对GaAs/AlAs多量子阱中受主对重空穴束缚能的影响。实验中所用的样品是通过分子束外延生长的一系列GaAs/AlAs多量子阱,量子阱宽度为3~20nm,并且在量子阱中央进行了浅受主Be原子的δ-掺杂。在4,20,40,80,120K不同温度下,分别对上述样品进行了光致发光谱测量,观察到了受主束缚激子从基态到激发态的两空穴跃迁,并且从实验上测得了在不同量子阱宽度下受主的束缚能。理论上应用量子力学中的变分原理,数值计算了受主对重空穴束缚能随量子阱宽度的变化关系,比较发现,理论计算和实验结果符合地较好。

Photoluminescence Study of the Acceptor Binding Energy in GaAs/AIAs Quantum Wells

We have investigated experimentally and theoretically the effect of quantum confinement on the acceptor binding energy in the GaAs/AlAs multiple-quantum well system, respectively. The system represents the maximum possible confinement for the acceptor states in the valence band and thus the maximum possible tuning range for the 1s-2p transition of the acceptor. A series of Be delta-doped GaAs/AlAs multiple quantum wells with the doping at the well center were grown on a semi-insulating (100) GaAs substrate by molecular beam epitaxy. The quantum-well width ranges from 3 to 20 nm. Each of multiple-quantum well structures investigated contained a same 5 nm wide AlAs barrier, while every GaAs well layer was delta doped at the well center with Be acceptor atoms. The doping level was 5×10¹⁰/cm². The photoluminescence spectra were measured at 4, 20, 40, 80, 120, and 200 K, respectively using Renishaw Raman imaging microscope. The optical excitation for photoluminescence experiments was provided by an argonion laser 514.5 nm. The excitation power was typically 5 mW. The two-hole transitions of the acceptor-bound exciton from the ground state, to the even-parity excited state, have been clearly observed. The acceptor binding energy of the shallow beryllium acceptor at the center of the multiple-quantum wells has been measured experimentally. Under the single-band effective mass and envelop function approximation, a variational calculation is presented to obtain the acceptor binding energy as a function of quantum-well width. We choose the produce of two terms as the trial wave function of a hole. The Bohr radius is employed as a variational parameter in order to minimize the total energy of the system. The total energy of the system can be solved for any choice of the Bohr radius by expanding the derivatives in finite differences and forming an iterative shooting algorithm. It is found that the experimental results are in good agreement with the theory.