Base doping effects in InGaAs/InP double heterostructure bipolar transistors

We have studied the performance characteristics of InGaAs/InP double heterostructure bipolar transistors grown by gas source molecular beam epitaxy. In particular the relationships between the current gain and the base doping level and the emitter junction surface to perimeter ratio were investigated in detail. For a base doping level as high as p∼3 × 10¹⁹cm^-3we find B∼100. Furthermore, we find no decrease in B with an increase in the perimeter to area ratio. The best frequency of unity current gain (fT) measured in small area devices is 18GHz.