A STUDY OF CARItiER EMISSION FROM GaAs/AlGaAs TRAPS AND QUANTUM WELLS UNDER PRESSURE

Abstract

Heterostructure devices are much superior to their homogeneous counterparts. However, due to band gap differences in heterostructures, off-sets exist in conduction and valence bands. For all kinds of applications, detailed understanding of the electronic properties of the heterostructures and the processes of carrier capture and exchange with the matrix material, in presence of off-sets, is of essential importance. Therefore, it's essential to know the magnitude of offsets in order to predict device behavior. The potential variation of a quantum well is similar to that of a deep trap, with some obvious differences. In spite of differences, quantum wells can thermally emit and capture carriers in much the same way as deep traps and, therefore, can behave as "giant" trapping centers. Exploiting this fact, in this work, the comprehensive and systematic study of semiconductor Quantum wells with capacitance transient spectroscopy under pressure is reported. The material system investigated is: GaAs/Al,,Gai.XAs Quantum Wells. From the temperature and pressure dependence of the emission rates, and the dependence of the DLTS signal on the bias conditions, conclusions are drawn on the carrier emission and band off-sets. Furthermore, the particularities of capacitance spectroscopy of QW systems are elucidated and equation for the carrier emission from QWs using 2-D density of states is presented