Stable multiplication gain in GaN p–i–n avalanche photodiodes with large device area

Abstract

Visible-blind p–i–n avalanche photodiodes (APDs) were fabricated with high-quality GaN epilayers deposited on c-plane sapphire substrates by metal-organic chemical vapour deposition. Due to low dislocation density and a sophisticated device fabrication process, the dark current was as small as ∼0.05 nA under reverse bias up to 20 V for devices with a large diameter of 200 µm, which was among the largest device area for GaN-based p–i–n APDs yet reported. When the reverse bias exceeded 38 V the dark current increased sharply, exhibiting a bulk avalanche field-dominated stable breakdown without microplasma formation or sidewall breakdown. With ultraviolet illumination (360 nm) an avalanche multiplication gain of 57 was achieved.