Influence of In-doping on the crystalline quality of GaAs epilayers on Si substrates

In-doping in GaAs epilayers has been investigated for GaAs epitaxial layers grown on Si substrates by metal organic vapor phase epitaxy. Insertion of an InGaAs strained interlayer combined with the thermal cycle annealing has been performed during growth In undoped GaAs epilayers the threading dislo cation density was 1.2 x 10(6)cm(-2) at the epilayer thickness of 4 mu m. B ut the threading dislocation density increased with the thickness above 4 m u m. The threading dislocation density increased with increasing growth tem perature from 620 to 670 degrees C. The results suggested that the thermal tensile strain degraded the GaAs layers on Si substrates. In In-doped GaBs layers grown on 4 mu m GaAs layers on Si substrates, the threading dislocat ion density of 6.5 x 10(5)cm(-2) was obtained. The microprobe photoluminesc ence measurement shows that the residual strain in In-doped GaAs layers on Si substrates was smaller than that in undoped GaAs layers on Si substrates at room temperature. The low residual strain was due to the compensation o f the tensile strain induced by the difference in thermal expansion coeffic ients between GaAs and Si materials by a compressive strain in In-doped GaA s on GaAs layers.