Comparative investigation of InP/InGaAs heterostructure-emitter tunneling and superlattice bipolar transistors

In this article, the characteristics of InP/InGaAs heterostructure-emitter bipolar transistors with 30 $\mathring{\mathrm{A}}$, 50 $\mathring{\mathrm{A}}$ $n$-InP layer tunneling layers and a five-period InP/InGaAs superlattice are demonstrated and comparatively investigated by experimentally results and analysis. In the three devices, a 200 $\mathring{\mathrm{A}}$ $n$-In$_{0.53}$Ga$_{0.47}$As layer together with an $n$-InP tunneling emitter layer (or $n$-InP/$n$-InGaAs superlattice) forms heterostructure emitter to decrease collector-emitter offset voltage. The results exhibits that the largest collector current and current gain are obtained for the tunneling transistor with a 30 $\mathring{\mathrm{A}}$ $n$-InP tunneling emitter layer. On the other hand, some of holes injecting from base to emitter will be blocked at $n$-InP/$n$-InGaAs heterojunction due to the relatively small hole transmission coefficient in superlattice device, which will result in a considerable base recombination current in the $n$-InGaAs layer. Therefore, the collector current and current gain of the superlattice device are the smallest values among of the devices.