Bulk photovoltaic effect and high mobility in the polar 2D semiconductor SnP <sub>2</sub> Se <sub>6</sub>
Vinod K. Sangwan, Daniel G. Chica, Ting-Ching Chu, Matthew Cheng, Michael A. Quintero, Shiqiang Hao, Christopher Mead, Hyeonseon Choi, Rui Zu, Jyoti Sheoran, Jingyang He, Yukun Liu, Eric K. Qian, Craig C. Laing, Min‐A Kang, Venkatraman Gopalan, Chris Wolverton, Vinayak P. Dravid, Lincoln J. Lauhon, Mark C. Hersam, Mercouri G. Kanatzidis
Abstract
The growth of layered 2D compounds is a key ingredient in finding new phenomena in quantum materials, optoelectronics, and energy conversion. Here, we report SnP 2 Se 6 , a van der Waals chiral ( R 3 space group) semiconductor with an indirect bandgap of 1.36 to 1.41 electron volts. Exfoliated SnP 2 Se 6 flakes are integrated into high-performance field-effect transistors with electron mobilities >100 cm 2 /Vs and on/off ratios >10 6 at room temperature. Upon excitation at a wavelength of 515.6 nanometer, SnP 2 Se 6 phototransistors show high gain (>4 × 10 4 ) at low intensity (≈10 −6 W/cm 2 ) and fast photoresponse (< 5 microsecond) with concurrent gain of ≈52.9 at high intensity (≈56.6 mW/cm 2 ) at a gate voltage of 60 V across 300-nm-thick SiO 2 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 2 at 20.6 W/cm 2 .