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

Abstract

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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bc</sub> (0/6 V), is 1.25 at a BV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ceo</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ce</sub> = 3 V and J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> = 25 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> = 200 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> stress under wafer-level electrical/thermal overstress tests.