LATTICE SITES OF SILICON IMPURITIES IN ALGAAS GROWN BY LIQUID-PHASE EPITAXY

Localised vibrational mode infrared absorption (10 K) and Hall measure ments were made on a series of Si doped AlxGa1-xAs samples with 0 less than or equal to x less than or equal to 0.25 grown by liquid phase e pitaxy. Localised vibrational modes were detected from Si-Ga donors, S i-As acceptors and Si-Ga-Si-As pairs which increased in frequency as x increased. The assignments of new lines observed at 386, 388 and 391 cm(-1) are discussed in relation to possible perturbations of the line s from Si-Ga or Si-As. The presence of DX centres was inferred from ob served persistent photoconductivity and attempts were made to relate t his result to the presence of the new IR lines.