The theory of auger recombination in quantum well heterostructures

Abstract

This thesis is concerned with calculations of the Auger recombination rate in direct gap semiconductors', it is composed of two parts: in the first and major part, the calculation of the CHCC Auger recombination process in a model of a quantum well heterostructure is considered; and in the second part, the overlap integrals between the cell periodic parts of the conduction band and heavy hole band Bloch functions are calculated using a 15-band full zone empirical K.p method. These overlap integrals are important factors in determining the Auger rate involving the recombination of electrons with heavy holes. The calculation of the quantum well CHCC Auger recombination rate differs from the bulk CHCC Auger calculations because carriers trapped in quantum wells reside within sub-bands associated with different bound states of the wells. The quantum well CHCC Auger recombination rate is thus calculated by considering all the possible intra and inter-sub-band carrier transitions (Hereafter referred to as bound-bound transitions). Processes in which the excited electron starts in a bound state of the well but makes a transition to an unbound state are also considered, and it is shown that although these 'bound-unbound' transitions have customarily been ignored, they can make a significant contribution to the Auger rate. Simple physical descriptions are then used to explain the relative importance of the processes, and numerical results are presented for the Auger rate in 1.3 um and 1.55 urn In GaAsP/InP quantum well systems. In these alloys it is found that the quantum well and bulk Auger rates are - very similar for the same carrier concentrations, and similar approximations. In the second part of this thesis conventional approximations for estimating conduction band - heavy hole with the wave vectors in the (001) direction, where the discrepancy is much larger, showing that the usual assumptions as to the dominant terms that appear ineffective mass rules, are incorrect. Also shown is the underestimation of the overlap ntegrals by the 4 band k.p method. Finally the significance of the results is discussed