A method to improve thermal management of power cells based on gallium arsenide (GaAs) heterojunction bipolar transistors (HBTs) fabricated with backside thermal via (BTV) technology is presented. For common-emitter configuration, collector metal is introduced to provide a new cooling path for heat spreading to BTVs flowing through the insulating layers. Two power cells consist of 64 HBTs, without (T64-A) and with (T64-B) the proposed cooling path are measured by QFI InfraScope TM temperature mapping system. Compared to T64-A, a reduction in the maximum junction temperature (Tj max) of T64-B by 22.55% (40.96°C) is observed when dissipated power (P diss) is 3 W and baseplate temperature (T base) is 25°C. Meanwhile, the thermal distribution of overall power cell is improved, and the improvements are 6.8, 21.67 and 35.96°C at T base = 25°C for three different values of P diss , which are 1, 2 and 3 W, respectively.