Design, fabrication and characterisation of an InP resonant tunneling bipolar transistor with double heterojunctions

An InP/In_0.53Ga_0.47As resonant tunnelling bipolar transistor with double heterojunction grown by molecular beam epitaxy and fabricated by selective wet chemical etching is presented. An In_0.53Ga_0.47As/AlAs resonant tunnelling diode which achieves a current density of 15 kA/cm² at a peak voltage of 1.6 V for a peak-to-valley ratio of 39:1 is integrated at the emitter of a double heterojunction InGaAs/InP bipolar transistor. Results are presented for 3 μm × 3 μm emitter size integrated device. A negative differential shape due to the resonant tunnelling effect at the emitter controlled by a 3.4 μA base current is observed in the common-emitter current-voltage characteristics at room temperature with a current density of 9.2 kA/cm² and a peak-to-valley ratio of 12:1. The maximum current gain of the device is 220. However beyond the resonant tunnelling peak, the resonant tunnelling transistor presents a bistability where the collector current collapses dramatically, the transistor characteristics are recovered by increasing the collector-emitter voltage.