Low frequency noise characteristics of self-aligned AlGaAs/GaAs power heterojunction bipolar transistors

The low frequency noise characteristics of modern self-aligned AlGaAs/GaAs power HBT's have been studied as a function of bias, temperature, frequency, and circuit topology. The devices have a 1/f/sup /spl gamma// behavior between 10 Hz and 100 Hz with 0.78/spl les//spl gamma//spl les/1.65. Strong deviation from 1/f/sup /spl gamma// is measured at higher frequencies due to trapping. The bias dependence of the collector noise ranged from I/sub C//sup 1.5/-I/sub C//sup 2.6/, while that for the base noise ranges from I/sub B//sup 0.7/-I/sub B//sup 2.5/. In all cases the collector noise is greater than the base noise. The base noise is apparently dominated by surface recombination noise and generation-recombination (G-R) noise. The collector noise is due to recombination mechanisms and G-R noise. The activation energy (E/sub a/) of the most significant trap is approximately 0.58 eV. The noise of the devices tested was found to be dominated by material and fabrication related mechanisms and not by fundamental mechanisms. >