Study of In_0.49Ga_0.51P/GaAs/In_0.49Ga_0.51P double δ-doped heterojunction bipolar transistor

A lattice-matched In_0.49Ga_0.51P/GaAs/In_0.49Ga_0.51P double δ-doped heterojunction bipolar transistor, prepared by low-pressure metal organic chemical vapor deposition (LP-MOCVD), is fabricated successfully and reported. Due to the insertion of δ-doped sheets and setback layers both at base-emitter (B-E) and base-collector (B-C) heterojunctions, the potential spikes are suppressed significantly. In addition, the electron blocking effect is removed and a dramatic improvement of current gain is obtained. A modified Ebers-Moll model is employed to study and analyse the device performances. The experimental results show that the common-emitter current gain over 210 at the collector current of 35 mA and an offset voltage Δ V_CE smaller than 50 mV are obtained. Also, a lower knee-shaped voltage of 1.4 V at the collector current of 40 mA is observed. These results indicate that the device studied is a good candidate for high-speed and high-power circuit applications.