Sanjun Yang, Lejing Pi, Liang Li, Kailang Liu, Ke Pei, Wei Han, Fakun Wang, Gang Cheng, Tianyou Zhai*, 2D Cu9S5/PtS2/WSe2 Double Heterojunction Bipolar Transistor with High Current Gain, Advanced Materials 2021, 2106537.
Abstract: Bipolar junction transistor (BJT), one important circuit element in the integrated circuits, is now widely used in high-speed computation and communication for its capability of high-power signal amplification. 2D materials and their heterostructures are promising in building high-amplification and high-frequency BJTs because they can be naturally thin and highly designable in tailoring components properties. However, currently the low emitter injection efficiency results in only moderate current gain achieved in the pioneer researches, severely restraining its future development. Herein, we show an elaborately designed double heterojunction bipolar transistor (DHBT) can greatly promote the injection efficiency, improving the current gain by order of magnitude. In this DHBT we use high-doping-density wide-bandgap 2D Cu9S5 as emitter and narrow-bandgap PtS2 as base. This heterostructure efficiently suppress the current ratio of reverse electron flux from base and increase the injection efficiency. By exploiting this high injection efficiency, our DHBT experimentally achieves an excellent common-base current gain (α = ~0.996) and common-emitter current gain ( β= ~910). This work systematically explores the electrical behavior of 2D materials based DHBT, and provides deep insight of the architecture design for building high gain DHBT, which may promote the applications of 2D-materials based heterojunctions in the fields of integrated circuits.
