High microwave power performance of self-aligned InGaP/GaAs heterojunction bipolar transistors

The results of experimental study and design criteria of high efficiency power heterojunction bipolar transistors (HBTs) are reported and discussed. Self-aligned npn HBTs fabricated by dry process technology have shown excellent device characteristics with low collector offset voltage (<150 mV) and low knee voltage (<0.7 V), and excellent high-frequency responses well into the millimeter-wave range. The FET-like device topology provides a means to preserve the power gain in device scaling for large emitter area. At X-band (10 GHz), an 8-cell common-base (CB) power transistor with emitter area of 240 μm² demonstrated 17.2-17.5 dB gain. The 12-cell (360 μm ²) common-emitter (CE) HBTs with a breakdown voltage (BV_ceo) of 11 V delivered 0.53 W output power with 57% power added efficiency (P.A.E.) and 11.3 dB power gain at 4 GHz. Peak power of 0.68 W, P.A.E. of 52%, and 10.3 dB power gain also was achieved at a collector current density of 5.5×10⁴ A/cm²