DONOR AND ACCEPTOR CONCENTRATIONS IN MOLECULAR-BEAM EPITAXIAL GAAS GROWN AT 300-DEGREES-C AND 400-DEGREES-C

The first Hall-effect measurements on molecular beam epitaxial GaAs la yers grown at the low temperatures of 300 and 400-degrees-C are report ed. Two independent methods were used to determine donor N(D) and acce ptor N(A) concentrations and activation energy E(D0), with the followi ng combined results: N(D) congruent-to 3 +/- 1 X 10(18), N(A) congruen t-to 1.5 +/- I X 10(17) CM-3 , and E(D0) = 0.645 +/- 0.009 eV for the 300-degrees-C layer; N(D) congruent-to 2 +/- 1 X 10(17), N(A) congruen t-to 7 +/- 3 X 10(16) CM-3 , and E(D0) = 0.648 +/- 0.003 eV for the 40 0-degrees-C layer. Thus, the deep donor is not the expected EL2, which has E(D0) = 0. 75 +/- 0.01 eV.