An electron-beam-induced current study of dislocations in GaAs

Abstract

Abstract Well-characterized α, β and screw dislocations have been created in GaAs specimens. Dislocation segments which thread the semiconductor surface at a known angle have been studied in terms of their behaviour as recombination centres and an analysis of the minority carrier diffusion length L D , has been performed. In liquid-encapsulated Czochralski (LEC) and liquid-phase epitaxy (LPE) material L D is small (less than 1.6 μm) and varies strongly with temperature and incident beam current. A simulation using numerical integration and a realistic Monte Carlo generation function has been developed which allows the electron-beam-induced current (EBIC) contrast of dislocations of any geometry to be modelled. This model shows that, due to variations in L D , the experimentally observed changes in EBIC contrast from dislocations in LEC and LPE material do not accurately reflect their fundamental recombination behaviour. The model can be used to obtain the actual recombination efficiency from the EBIC contrast data. Dislocation in metal organic chemical-vapour-deposited material showed recombination behaviour different from that observed in the LEC and LPE specimens. A new effect has been discovered whereby some dislocations increase their recombination strength when irradiated with an electron beam at 30 kV. The rate of increase is directly proportional to the beam current of the irradiation and the effect is greater for screw dislocations than for β dislocations.