Influence of emitter ledge width on the characteristics of InGaP/GaAs heterojunction bipolar transistors

A comprehensive study of the InGaP ledge width effect on the performance of InGaP/GaAs heterojunction bipolar transistors (HBTs) is demonstrated. It is shown that the electron density and recombination rate at the surface channel are decreased with increasing the InGaP ledge width. However, the longer InGaP ledge width increases the base-collector junction area which in turn deteriorates the high frequency performance. According to the theoretical analysis and experimental results, the device with an InGaP ledge width of 0.8 mum shows the best and acceptable DC and RF performance.