Carbon doping for the GaAs base layer of Heterojunction Bipolar Transistors in a production scale MOVPE reactor

In this work different approaches for carbon doping of GaAs in MOVPE are compared with respect to their growth-and device-related material properties. Doping levels up to 6 x 10(19) cm(-3) and smooth surface morphologies are achieved with either intrinsically (TMG and AsH3 or TMAs) or extrinsically (CBr4) doped layers. Despite comparable structural and majority carrier properties differences in GaInP/GaAs-HBT device performance depending on base doping conditions are obtained. Devices with an intrinsically doped base layer (TMG + AsH3) show superior transistor performance with a current gain to base sheet resistance ratio (beta /R-sb) exceeding 0.5 for base thicknesses as large as 120 nm. The use of either CBr4 or TMAs as base growth precursors results in reduced current gains (beta /R-sb less than or equal to 0.3). It is shown that the achieved HBT current gain is directly related to recombination centers in the heavily doped base layer depending on doping method. (C) 2000 Elsevier Science B.V. All rights reserved.