High performance Al0.35Ga0.65As/GaAs HBT's

AlGaAs emitter heterojunction bipolar transistors (HBT's) are demonstrated to have excellent de and RF properties comparable to InGaP/GaBs HBT's by in creasing the Al composition. Al0.35Ga0.65As/GaAs HBT's exhibit very high de current gain at all bias levels, exceeding 140 at 25 A/cm(2) and reaching a maximum of 210 at 26 kA/cm(2) (L = 1.4 mu m x3 mu m, R-sb = 330 Omega/squ are). The temperature dependence of the peak de current gain is also signif icantly improved by increasing the AlGaAs mole fraction of the emitter. De, ice analysis suggests that a larger emitter energy-gap contributes to the i mproved device performance by both lowering space charge recombination and increasing the barrier to reverse hole injection.