EFFECT OF BAND TAILING AND DONOR LEVELS ON GaAs INJECTION LASER UNDER PRESSURE

Abstract

This thesis embodies the investigation on the injection current of GaAs laser_. Many physical properties can be known through the behaviour of injection current at high pressures. The theoretical analysis is based on an examination of the relative distribution of the charge carriers in valleys 1 and 2 as the crystal is subjected to hydrostatic pressure. We have considered the donor levels associated with the second valley and the band tail with the first valley (000) conduction band. The effect of donor levels is ooserved theoretically only at higher pre-ssures, where they start contributing electrons in the first valley. The effect of band tailing is to decra-ase the number of carriers in the first valley of conduc-tion band with the increase of pressure. Injection current is calculated in terms of charged carriers that are contributed by valley 1 and valley 2, and it is found to be fairly constant with prdssure and increases slightly at higher pressures. The injection current is calculated by taking into account the electrons trapped into the band tail also. We observe that the injection current has a tendency to rise with pressure due to band tailing effect. In practice, however, it remains fairly steady but droops slightly at higher pressures fox GaAs laser.,