Heavily carbon-doped GaAsSb grown on InP for HBT applications

We present the results of Hall measurements on heavily carbon-doped GaAsSb epilayers grown by metalorganic chemical vapour deposition (MOVPE) on InP s ubstrates. An extremely strong alloy scattering effect is observed in this material, dominating the Hall mobility even at doping levels in the 10(19) range. This effect is due to the very large (1 eV) valence band offset betw een GaAs and GaSb. Despite the strong alloy scattering, conductivities as h igh as 890 S/cm were observed at doping levels above 10(20) cm(-3). CCl4 an d CBr4 were investigated as p-type dopants. Hole concentrations of up to 1. 4 x 10(20) and 3.0 x 10(20) cm(-3) were obtained at growth temperatures of 560 degreesC and 500 degreesC, respectively. For both carbon sources, a str ong reduction in growth rate and Sb incorporation rate was observed with in creasing dopant concentration at 560 degreesC. Carbon incorporation was obs erved to increase linearly with Sb solid phase mole fraction. (C) 2000 Else vier Science B.V. All rights reserved.