Comparative studies of InP/InGaAs single and double heterojunction bipolar transistors with a tunnelling emitter barrier structure

The DC performances of InP/InGaAs single and double heterojunction bipolar transistors (SHBT and DHBT) are compared and studied. The temperature-dependent characteristics of both devices are also presented. Due to the use of a 4000 Å InP collector, the studied DHBT exhibits a higher breakdown voltage than the SHBT. The common-emitter breakdown voltages of the studied SHBT and DHBT are higher than 2 and 10 V, respectively. In addition, based on the employment of a tunnelling emitter barrier, the emitter injection efficiency is improved substantially, so a very low offset voltage (<50 mV) is obtained for the studied SHBT device. Furthermore, the common-emitter DC current gain of the studied SHBT is relatively independent of the temperature at low and middle current regimes. On the other hand, the studied DHBT has a smaller current gain due to the collector current blocking effect described.