A multi-finger power SiGe heterojunction bipolar transistor （HBT） with non-uniform finger spacing was fabricated to improve thermal stability. Experimental results show that the peak temperature is reduced by 22K compared with that of an HBT with uniform finger spacing in the same operating conditions. The temperature profile across the device can be improved at different biases for the same HBT with non-uniform finger spacing. Because of the decrease in peak temperature and the improvement of temperature profile, the power SiGe HBT with non-uniform spacing can operate at higher bias and hence has higher power handling capability.
