基于量子限制的受主带间跃迁太赫兹探测器的制备与测量

使用分子束外延生长设备,在GaAs（100）衬底上生长了量子阱宽度为3 nm的GaAs/AlAs多量子阱样品,并在量子阱层中央进行了Be受主的δ-掺杂。根据量子限制受主从束缚态到非束缚态之间的跃迁,设计并制备了δ-掺杂Be受主GaAs/AlAs多量子阱太赫兹光探测器原型器件。在4.2 K温度下,分别对器件进行了太赫兹光电流谱和暗电流-电压曲线的测量。在6 V直流偏压下,空穴载流子沿量子阱层方向输运。当正入射激光频率为6.8 THz时,器件响应率为2×10^-4 V/W（2 μA/W）。通过器件的暗电流-电压曲线计算了器件全散粒噪声电流,在4.2 K、6 V直流偏压下,全散粒噪声电流为5.03 fA·Hz^-1/2。     

Raman spectrum study of δ-doped GaAs/AlAs multiple-quantum wells

Three samples of GaAs/AlAs multiple-quantum wells with different quantum well widths and δ-doped with Be acceptors at the well center were grown on(100) Ga As substrates by molecular beam epitaxy. Polarized Raman spectra were recorded on the three samples at temperatures in a range of 4-50 K in a backscattering configuration. The two branches of coupled modes due to the interaction of the hole intersubband transitions and the quantum-well longitudinal optical(LO) phonon were observed clearly. The evaluation formalism of the Green function was employed and each lineshape of the Raman spectrum of the coupled modes was simulated. The dependence of the peak position of Raman shifts of the two coupled modes as well as the quantum-well LO phonon on the quantum-well size and measured temperature were given, and the coupling interaction mechanism between the hole subband transitions and the quantum-well LO phonon was researched.     

掺杂在GaAs材料中Be受主能级之间的跃迁

通过远红外吸收谱、光致发光光谱和拉曼散射光谱,对均匀掺杂在GaAs材料中Be受主能级之间的跃迁进行了研究.实验中使用的GaAs:Be样品是通过分子束外延设备,生长在半绝缘(100) GaAs衬底之上的外延单层.在4.2 K温度下,对样品分别进行了远红外吸收光谱、光致发光光谱、Raman光谱的实验测量.在远红外吸收光谱中,清楚地观察到了从Be受主1S_(3/2)Γ_8基态到它的三个激发态2P_(3/2)Γ_8, 2P5/2Γ_8和2P5/2Γ_7之间的奇宇称跃迁吸收峰.跃迁能量与先前文献中报道的符合得很好.从光致发光光谱中,观察到了Be受主从1S_(3/2)Γ_8基态到2S_(3/2)Γ_8激发态的两空穴跃迁的发光峰,从而间接地找到了两能级之间的跃迁能量.在Raman光谱中,清楚地分辨出来了Be受主从1S_(3/2)Γ_8基态到2S_(3/2)Γ_8激发态偶宇称跃迁的拉曼散射峰,直接得到了两能级间的跃迁能量.对比发现,分别直接和间接得到的1S_(3/2)Γ8基态到2S_(3/2)Γ8激发态跃迁能量结果是一致的.     

Excitonic transitions in Be-doped GaAs/AlAs multiple quantum well

A series of GaAs/AlAs multiple-quantum wells doped with Be is grown by molecular beam epitaxy. The photoluminescence spectra are measured at 4, 20, 40, 80, 120, and 200 K, respectively. The recombination transition emission of heavy-hole and light-hole free excitons is clearly observed and the transition energies are measured with different quantum well widths. In addition, a theoretical model of excitonic states in the quantum wells is used, in which the symmetry of the component of the exciton wave function representing the relative motion is allowed to vary between the two- and threedimensional limits. Then, within the effective mass and envelope function approximation, the recombination transition energies of the heavy- and light-hole excitons in GaAs/AlAs multiple-quantum wells are calculated each as a function of quantum well width by the shooting method and variational principle with two variational parameters. The results show that the excitons are neither 2D nor 3D like, but are in between in character and that the theoretical calculation is in good agreement with the experimental results.