Fig. 1: Electroluminescence based on WSe2/hBN/CrI3 heterostructure.
a Schematic of the device structure. The back gate Vbg and top gate Vtg are used to control the doping of CrI3 and WSe2. The bias voltage Vbias is applied across the vertical junction going through the hBN tunneling barrier. hν indicates the emitted photon with circular polarization σ±. b The whitelight microscopic image of a monolayer WSe2/hBN/bilayer CrI3 device. The scale bar is 10 μm. The monolayer WSe2 is outlined by red dashed lines, blue dashed lines outline CrI3, the thin hBN (~2.5 nm) tunneling layer is denoted by the green dashed lines, and the source and drain contacts (from graphite stripes) are denoted by the gray lines. c Spatially-resolved electroluminescence (EL) image of the device. The notation of dashed lines is the same as b. The scale bar is 10 μm. The EL signal comes from the overlapped area of the source and drain contacts. d I–V characteristics of the heterostructure at different top gate voltages while keeping Vbg = 0 V. The red triangles denote the extracted threshold point for EL generation. e Band alignment schematics of the heterostructure under different bias voltages during EL generation with a positive Vbias (upper panel, WSe2 n-doped) and no EL generation with a negative Vbias (lower panel). The arrows indicate the direction of carrier tunneling and the dashed ellipse represents the exciton. f EL spectra at different Vbias with Vtg = 1 V and Vbg = 0 V. The inset shows the comparison of the normalized photoluminescence (PL) and EL spectra. The PL spectra was taken with a 633 nm continuous wave laser (10 μW). The EL spectrum was measured under Vbias = 2.5 V, Ibias = 0.49 μA with Vtg = 1 V.
