Joint Study on the Novel Semiconductor Nanostructures

研究了量子限制和晶格驰豫对GaAs/In_&lt；0.2&gt；Ga_&lt；0.8&gt；As/GaAs量子点电子态的影响。用电子束曝光法和湿法化学腐蚀法制备了量子点，并用光致发光测量研究了量子点的电子态。观察到较小量子点的跃迁能发生明显的蓝移，而较大量子点的跃迁能向较低的能量方向移动。蓝移归因于量子限制，红移归因于晶格弛豫。给出了一个简单的经验公式，它很好地描述了观测到的能量移动。还研究了朗道量子化超晶格的Wannier-Stark区域中的跳跃传导。我们测量了GaAsAlAs超晶格的电流-电压特性，并考虑声形变相互作用对其进行了分析，发现在高势垒超晶格中出现了两种不同反共振条件的反共振。其中一种反共振是由势垒间位相因素引起的，反共振条件与超晶格周期有关。另一种类型的反共振是由井内相位因素引起的，反共振条件取决于井宽。由于超晶格周期与势垒宽度不同，两种类型的反共振一般都是在异相中发生的。然而，在一定的电压范围内，两种反谐振是同相发生的，并且在电流-电压特性中表现出明显的反谐振。

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.