Metamorphic InP/InGaAs heterojunction bipolar transistors under high-current and high temperature stress

The reliability of InP/InGaAs metamorphic heterojunction bipolar transistors (MHBTs) on GaAs substrates under excessive current density (100 kA/cm/sup 2/) at high junction temperature (250/spl deg/C) has been tested. Experimental data indicate that, by proper growth optimization of the strain relief buffer layer, MHBTs on GaAs substrates with electrical stability similar to that of HBTs on InP substrates could be achieved. It has been found that compared to MHEMTs, growth of a high quality metamorphic buffer is more critical for the stability of MHBTs.