Bulk photovoltaic effect and high mobility in the polar 2D semiconductor SnPSe.

The growth of layered 2D compounds is a key ingredient in finding new phenomena in quantum materials, optoelectronics, and energy conversion. Here, we report SnPSe, a van der Waals chiral (3 space group) semiconductor with an indirect bandgap of 1.36 to 1.41 electron volts. Exfoliated SnPSe flakes are integrated into high-performance field-effect transistors with electron mobilities >100 cm/Vs and on/off ratios >10 at room temperature. Upon excitation at a wavelength of 515.6 nanometer, SnPSe phototransistors show high gain (>4 × 10) at low intensity (≈10 W/cm) and fast photoresponse (< 5 microsecond) with concurrent gain of ≈52.9 at high intensity (≈56.6 mW/cm) at a gate voltage of 60 V across 300-nm-thick SiO dielectric layer. The combination of high carrier mobility and the non-centrosymmetric crystal structure results in a strong intrinsic bulk photovoltaic effect; under local excitation at normal incidence at 532 nm, short circuit currents exceed 8 mA/cm at 20.6 W/cm.