NATIVE DONORS AND ACCEPTORS IN MOLECULAR-BEAM EPITAXIAL GAAS GROWN AT 200-DEGREES-C

Absorption measurements at 1.1 and 1.2-mu-m were used along with the known electron and hole photoionization cross sections for EL2 to determine deep donor (EL2-like) and acceptor concentrations N(D)=9.9X10(19) and N(A)=7.9X10(18) cm-3, respectively, in a 2-mu-m-thick molecular-beam epitaxial GaAs layer grown at 200-degrees-C on a 2-in.-diam semi-insulating wafer. Both lateral and depth uniformities of N(D) over the wafer were excellent as was also the case for the conductivity. Band conduction was negligible compared to hopping conduction at 296 K as evidenced by the lack of a measurable Hall coefficient.