AN OPTICAL CHARACTERIZATION OF DEFECT LEVELS INDUCED BY MBE GROWTH OF GAAS

GaAs layers grown under As//4 flux at 585 degree C by MBE (p-type NID layers and n-type doped layers) have been studied by photoluminescence at 1. 9 K (UV excitation, selectively excited photoluminescence, and excitation spectroscopy). The photoluminescence lines between 1. 5110 and 1. 5040 ev ascribed to excitons bound to point defects associated with the use of an As//4 source have been more carefully studied in order to specify the nature of the transitions involved. Two hole spectra, and donor acceptor pair bands analysis allow to identify the excited states of two acceptor levels. The first one is attributed to the carbon contamination, the second one to which the 1. 5109 ev exciton is bound is also a shallow acceptor level showing a negative chemical shift and a binding energy of 22. 9 Mev.