Bilateral Geiger mode avalanche in InSe Schottky photodiodes

Avalanche photodiodes (APDs) are crucial in emerging weak light signal detection fields. The major challenge of high-performance APDs is to achieve both an ultrahigh gain and ultralow breakdown voltage. The key to efficient carrier multiplication is searching for a high-mobility semiconductor and constructing a novel device structure with an alternative mechanism. Herein, we demonstrate the bilateral Geiger mode avalanche in two-dimensional (2D) Graphene/InSe/Cr asymmetrical Schottky junction (SJ) APDs. An ultrahigh gain of 6.3 × 107 is yielded at an extremely low breakdown voltage down to 1.4 V approaching its threshold limit of bandgap of InSe. A positive temperature coefficient of the ionization rate and an ultralow critical electric field (11.5 kV/cm) are present in the Graphene/InSe/Cr SJ APDs (GISC-SJ APDs). These support the low-bias triggering impact ionization and low-loss carrier multiplication for outstanding performance along with the unique asymmetric Schottky barrier configurations. Such device architecture enables an ultralow dark current of 100 fA, and a high sensitivity with weak light signals detection ability down to around 2900 photons at room temperature. These characteristics show the prospects of the asymmetrical InSe SJs for developing energy-efficient and high-gain APDs.