Bilateral Geiger mode avalanche in InSe Schottky photodiodes

Avalanche photodiodes are crucial in emerging weak light signal detection fields. However, most avalanche photodiodes either suffer from relatively high breakdown voltage or relatively low gain, impairing the advantages of avalanche multiplication. Herein, we report the bilateral Geiger mode avalanche in two-dimensional Graphene/InSe/Cr asymmetrical Schottky junction. A high gain of 6.3 × 10⁷ is yielded at low breakdown voltage down to 1.4 V approaching InSe's threshold limit of bandgap. In addition to the separated carrier injection region and avalanche multiplication region, a positive temperature coefficient of the ionization rate and a very low critical electric field (11.5 kV cm^-1) are demonstrated, leading to the nice performance. Such device architecture also enables low dark current and noise equivalent power, showing weak light signals detection ability down to around 35 photons at room temperature. This study provides alternative strategies for developing energy-efficient and high-gain avalanche photodiodes.