An InP/InGaAs metamorphic δ-doped heterojunction bipolar transistor with high current gain and low offset voltage

Excellent dc performance of an InP/InGaAs metamorphic δ-doped heterojunction bipolar transistor (HBT) using a linearly graded InxGa1 − xP metamorphic buffer layer grown on GaAs substrate is demonstrated. The employment of a δ-doped sheet between two undoped spacer layers could eliminate the potential spike at base–emitter junction and increase the effective barrier, which could prevent the hole injection from base into emitter. A maximum current gain of 255, a low offset voltage of 105 mV, and a small second (third) harmonic distortions of 0.545 (− 0.05) at VCE = 2.5 V are obtained. The current gain and offset voltage are the best values than that of the previous InP/InGaAs metamorphic HBT.