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Electroluminescence & Photocurrent Generation from InSe-GaSe Heterojunction

Heterostructures of 2D van der Waals semiconductor materials o er a diverse play-ground for exploring fundamental physics and potential device applications. In InSe/GaSe heterostructures formed by sequential mechanical exfoliation and stacking of 2D monochalco- genides InSe and GaSe, we observe charge transfer between InSe and GaSe due to the 2D van der Waals interface formation and a strong hysteresis e ect in the electron transport through the InSe layer when a gate voltage is applied through the GaSe layer. A gate voltage dependant conductance decay rate is also observed. We relate these observations to the gate voltage dependant dynamical charge transfer between InSe and GaSe layers.

Additional data for charge transfer experiment

(a) Gate-transfer curves (𝑉𝑔 scanning rate = 13.33 V/s) before and after GaSe transfer for an additional sample (InSe sample 2) – sample structure and experiment is the same as described in Figure 2 in main text. Arrows indicate Vg scanning directions.

(b),(c) I-V characteristics of an InSe FET device (InSe Sample 1 –Figure 2 in main text) before and after GaSe transfer and anneal, respectively. Applied Vg values are indicated in the plots.

Gate-transfer characteristics of bare InSe and GaSe devices

Room temperature gate-transfer characteristics at Vsd=1V for a bare GaSe device on 300 nm SiO2 substrate (Vg scanning rate = 13.33 V/s).

Gate-transfer characteristics of bare InSe and GaSe devices

Room-temperature gate-transfer characteristics at Vsd = 0.1V for bare fewlayer (20 nm thick) InSe FET at different scanning rates, measured in vacuum of 50mTorr (Arrows indicate Vg scanning directions). These measurements were done on devices fabricated and annealed under the same conditions as described for the InSe/GaSe heterostructures in main text.

characteristics of InSe-GaSe heterostructures

Room temperature I-V characteristics at different gate-voltages for the InSe-GaSe heterostructure sample shown in Figure 3 in main text. For each set gatevoltage value, source-drain voltage was swept from -0.5V to 0.5V in 1s, before setting the next gate-voltage value. I-V scans were done from low to high gate-voltage

Surface characterization of InSe and GaSe nanoflakes

Atomic Force Microscopy surface characterization of (a) InSe and (b) GaSenanoflakes from the same bulk crystals and exfoliated using the same methods as usedin this study. Red dotted line in inset image of flakes marks the scan region. (c),(d) show corresponding scans to estimate flake thickness.

Note that the AFM scans shown in Figure S5(c) and (d) were done at a lower resolution over a larger thickness range with the purpose of estimating flake thickness and therefore do not reflect the actual surface profile of the flakes. Flake thickness: InSe –25 nm, GaSe – 6 nm.

Temperature dependent gate-transfer characteristics of InSe-GaSe heterostructures

Gate-transfer curves (𝑉𝑔 scanning rate = 13.33 V/s) at different temperatures for InSe-GaSe heterostructure sample – same data as shown in Figure 6 in main text, device structure in Figure 3 of main text.

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