Non-Abrupt Junctions InP DHBT Power Amplifier in Class-AB CDMA Operation

InGaAs/InP double heterojunction bipolar transistors (DHBTs) with non-abrupt junctions have been utilized to achieve a high efficiency class-AB CDMA power amplifier (PA). InGaAs/InAlAs superlattice layers are inserted at the emitter-base junction and the base-collector junction to remove abrupt barriers in the conduction band. These non-abrupt junctions provide a low knee voltage in collector current-voltage characteristics, enabling a high efficiency, low distortion operation. We fabricated a large emitter-periphery device of 320 mum
²
and obtained a 16.0 dBm output power with 54% PAE, at a -41 dBc adjacent channel leakage power ratio (ACLR) and a supply voltage of 3.5 V in a 900 MHz WCDMA class-AB operation. The total collector current consumed is 21 mA. Using InP-related materials, we will realize PA modules with low supply voltages for future mobile communication systems