SILICON DONOR-ACCEPTOR PAIR DEFECTS IN GALLIUM-ARSENIDE

Absorption bands at 393 cm-1 and 464 cm-1 in GaAs are due to the localised vibrational modes (LVMs) of nearest-neighbour (Si Ga-SiAs) defects. A third line at 367 cm-1 has been attributed to this defect but there have been doubts about the assignment. Samples have now been subjected to prolonged 2 meV electron irradiations and subsequent anneals, and it is shown that the strength of the absorption at 367 cm-1 is not correlated with that of the line at 393 cm-1. Thus the defect responsible for the 367 cm-1 line is not the pair centre and the defect is designated (Si-Y). Another grown-in centre (Si-X) gives an LVM line at 369 cm-1 and it is now shown that other silicon impurities do not give rise to detectable infrared absorption.