Cleavage Processes and Steps in Semiconductors

Abstract

The nature ,of cleaved surfaces on Si and some III-V compounds is discussed. Measurements of luminescence produced by cleavage in vacua and ambients, provide information about the nature of the surfaces and crack progression. Long duration signals from Si have provided evidence for the presence of an indirect gap in the surface states, of magnitude 0.2 — 0.5 eV, and the quenching of luminescence in air leads to deduction of the presence of a small potential well at the clean surface. GaAs and also InP show much shorter signals, corresponding to the time of crack progression, and these are not quenched in air. This is explained by the much smaller surface state density and hence potential well. The crack can show partial stalling and healing if the applied forces are not sufficiently strong, supporting models of surface structure which do not feature drastic atomic rearrangements. The steps found on cleaved surfaces have been modelled and the energies calculated for several cases. Results are summarised.