Performance of High-Reliability and High-Linearity InGaP/GaAs HBT PAs for Wireless Communication

An InGaP heterojunction-bipolar-transistor (HBT) power amplifier with the best linearity and high reliability is presented in this paper for use in wireless digital mobile communication systems. We optimized the linearity of a novel HBT device and investigated its reliability. Using SILVACO software, we performed a simulation of the HBT device. The best linearity, which was revealed for the device with a capacitance ratio C_bc (0/6 V), is 1.25 at a BV_ceo of 22 V. After the device was fabricated, a reasonably high PAE, i.e., ~ 55%, was obtained at 2.0 GHz, and an adjacent channel power ratio of over -48 dBc was achieved. In the reliability testing, the device, which was stressed at V_ce = 3 V and J_C = 25 kA/cm² under 85°C ambient temperature and 85% humidity, showed no failure for more than 1100 h. No significant beta degradation was observed under an extreme current J_C = 200 kA/cm² stress under wafer-level electrical/thermal overstress tests.