Fig. 1: Bipolar-barrier tunnel heterostructures design and device optimization.
From: Bipolar-barrier tunnel heterostructures for high-sensitivity mid-wave infrared photodetection
a Schematic diagram of the BPt/MoTe2/BPb bipolar-barrier tunnel heterostructure with a Au reflector. BPt, top black phosphorus; BPb, bottom black phosphorus. b Band profiles of BPt, MoTe2, BPb before contact. c Simulated absorption for the BPt/MoTe2/BPb heterostructures on a 50 nm Au reflector, as a function of the BP layer thickness. The thickness of MoTe2 is set to 20 nm. d Band alignment of the heterostructure under a negative bias and mid-wave light illumination. Dark carriers and photogenerated carriers in BP are marked in gray and red, respectively. Under mid-infrared light illumination, the effective barrier height in the valence bands of BP/MoTe2 heterostructure decreases compared to the dark condition, promoting quantum tunneling of photo hole carriers and resulting in significant tunneling photocurrents. And the photogating effect induced by trap states in BP modulates carriers transport dynamics, contrbuting to gain. φD and φL refer to the effective barrier height in the dark and under light illumination, respectively
