AlGaN-based solar-blind UV heterojunction bipolar phototransistors: structural design, epitaxial growth, and optoelectric properties

Abstract

An AlGaN-based solar-blind UV heterojunction bipolar phototransistor (HBPT) with an AlGaN-based multiple quantum well (MQW) layer as the light absorption layer is proposed in this paper. On the basis of the individually optimized growth of the MQW light absorption layer and the p-type AlGaN base layer, the material growth, device preparation, and performance evaluation of the solar-blind UV HBPT are investigated in detail. The evaluations show that the fabricated two-end NPN-type phototransistor with a floating base presents a low dark current density of about 4.8 × 10⁻⁸ A cm⁻² and a high peak responsivity of 4.55 A W⁻¹ at 267 nm as the device is biased at a V_CE of 12 V, corresponding to a high EQE of 2.1 × 10³%. It also exhibits a quick transient response speed of 13.47 ns at a lower bias voltage (V_CE = 3 V). These results favorably prove the feasibility of realizing a high performance solar-blind UV photodetector based on the AlGaN-based MQW HBPT.