Joint Study on the Novel Semiconductor Nanostructures

研究了量子限制和晶格弛豫对GaAs/In_<0.2>Ga_<0.8>As/GaAs量子点中电子态的影响。采用电子束光刻和湿法化学刻蚀技术制备了量子点，并对其电子态进行了光致发光测量。小量子点的跃迁能量发生蓝移，而大量子点的跃迁能量向低能方向移动。蓝移归因于量子限制，而红移归因于晶格弛豫。给出了一个简单的经验公式，很好地描述了观测到的能量移动，并研究了Landau量子化超晶格的Wannier-Stark区的跳跃导电。我们测量了GaAs/AlAs超晶格的电流-电压特性，并考虑了声形变相互作用对它们进行了分析，发现在高势垒的超晶格中存在两种不同反共振条件的反共振。一种类型的反共振是由于阱间相位因子和反共振条件取决于超晶格周期。另一种类型的反共振是由于阱内相位因子和反共振条件依赖于阱宽。由于超晶格周期与阱宽不同，这两种反共振一般发生在反相。在一定的电压范围内，两种反谐振现象同相发生，且反谐振现象在电流-电压特性曲线上表现得很明显。

Effect of quantum confinement and lattice relaxation on electronic states in GaAs/In_<0.2>Ga_<0.8>As/GaAs quantum dots has been studied. The quantum dots were fabricated by using electron beam lithography and wet chemical etching, and the photoluminescence measurements have been carried out to investigate the electronic states. Blue shift in the transition energy for smaller quantum dots was clearly observed, while the transition energy shifts to lower energy for larger dots. The blue shift is attributed to quantum confinement and the red shift to lattice relaxation. A simple empirical formula is given which well describes the observed energy shift.Hopping conduction in the Wannier-Stark reginme of a Landau-quantized superlattice has also been studied. We have measured current-voltage characteristics in GaAs/AlAs superlattices, analyzed them by taking into account acoustic deformation interaction, and find that two types of anti-resonances with different anti-resonance conditions occur in superlattices having high potential barrier. One type of the anti-resonances is due to the inter-well phase-factor and the anti-resonance condition depends on the superlattice period. The other type of the anti-resonances is due to the intra-well phase-factor and the anti-resonance condition depends on the well width. Since the superlattice period is different from the well width, the two types of anti-resonances occur in out phase in general. For a certain voltage region, however, the two types of anti-resonances occur in phase, and the anti-resonances are found to appear clearly in current-voltage characteristics.