Approaching the Intrinsic Threshold Breakdown Voltage and Ultrahigh Gain in a Graphite/InSe Schottky Photodetector

Abstract

Realizing both ultralow breakdown voltage and ultrahigh gain is one of the major challenges in the development of high-performance avalanche photodetector. Here, it is reported that an ultrahigh avalanche gain of 3 × 10⁵ can be realized in the graphite/InSe Schottky photodetector at a breakdown voltage down to 5.5 V. Remarkably, the threshold breakdown voltage can be further reduced down to 1.8 V by raising the operating temperature, approaching the theoretical limit of 1.5 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics> <mml:mrow><mml:msub><mml:mi>E</mml:mi> <mml:mi>g</mml:mi></mml:msub> </mml:mrow> <mml:annotation>\[{{\cal E}_{\bf g}}\]</mml:annotation></mml:semantics> </mml:math> /e, with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics> <mml:mrow><mml:msub><mml:mi>E</mml:mi> <mml:mi>g</mml:mi></mml:msub> </mml:mrow> <mml:annotation>${{\cal E}_{\bf g}}$</mml:annotation></mml:semantics> </mml:math> the bandgap of semiconductor. A 2D impact ionization model is developed and it is uncovered that observation of high gain at low breakdown voltage arises from reduced dimensionality of electron-phonon scattering in the layered InSe flake. These findings open up a promising avenue for developing novel weak-light detectors with low energy consumption and high sensitivity.