Functional Double-Emitter HPTs with Different Emitter-Area Ratios

Differing from those conventional HPTs with and without the base electrode reported in the past, we introduce a three-terminal heterojunction phototransistor with double emitters (DE-HPT). The double emitters in the HPT are designed to exhibit a series of different area ratios (A1:A2), but the same total area. Furthermore, the two emitters together with the common collector form a new three-terminal device. Instead of current-bias base, a voltage-bias emitter is used to tune the collector photocurrent. It is found that the collector photocurrent for the DE-HPT is enhanced and tunable when compared to a SE-HPT (single emitter-HPT) with the same total emitter area. In addition, a circuit model with three sets of parallel diodes is employed to explain how the enhancement can be seen.