Low-Dark-Current and Wide-Dynamic-Range InGaAs/InAlAs Avalanche Photodiodes with a Dual-Charge Layer

This study explores the impact of a dual-charge layer structure on the performance of InGaAs/InAlAs avalanche photodiodes (APDs) with a separate absorption, charge, multiplication, charge, and transit (SACMCT) structure. The dual-charge layer, consisting of p-doped and n-doped charge layers on either side of the avalanche layer, is designed to precisely control the internal electric field, effectively reduce the dark current, and extend the dynamic range. Simulation results guided the fabrication of a backside-illuminated APD, which achieved a linear operating range of 10–30 V and a dark current as low as 80 nA. The optimized design significantly reduced the dark current and increased the breakdown voltage compared to previously reported APDs. These improvements demonstrate the potential of dual-charge-layer APDs for high-speed optical communications and precision photodetection applications.