Abstract
The power performance of InP based single HBTs has been mediocre compared with their double HBTs counterpartsdue to their inherently low breakdown voltage. [ 11 For power amplifiers requiring moderate output power levels, singleHBTs are more cost effective due to their simplicity of fabrication and design. InP-based single HBTs have demonstratedpower performance at lOGHz of 1.37mW/pm2, lldB gain and 33.9% power-added-efficiency [2]. In this work, a gradedInAlAshGaAs emitter base junction and a lowdoped thick collector was employed to lower the turn-on voltage andincrease the breakdown voltage respectively. InAlAdInGaAs single HBTs were subsequently fabricated with undercutcollectors for reduced base-collector capacitance. A 4-finger 2x10 pm2 HBT unit cell exhibited 22.5 dBm continuouswave (CW) output power (2.23mW/pm2 power density), 35% power-added-efficiency and an associated gain of 10.5dB at1OGHz. To our knowledge, this is the best output power density performance for InP based single HBTs.