ANOMALIES OF OHMIC CONTACTS ON HETEROEPITAXIAL GAAS-LAYERS ON SI AFTER RAPID THERMAL ANNEALING

This paper reports on resistance and capacity measurements of ohmic contacts which were deposited on heteroepitaxially grown, Si-doped GaAs layers on Si substrates. It is observed that the process of rapid thermal annealing (RTA) considerably affects the ohmic properties of subsequently deposited contacts. With rising annealing temperature, the electrical resistivity in the GaAs layer and thus, the contact resistance increased essentially. Although the chemical concentration profile of Si dopants is not changed by RTA, the number of electrically active carriers is lowered. Photoluminescence measurements confirm that Si donors on Ga sites perform a site exchange to As vacancies, thereby forming Si acceptors. The extent of this exchange process is considerably enhanced by the presence of a high dislocation density in the heteroepitaxial GaAs films. © 1995 American Institute of Physics.