Suppression of Persistent Photoconductivity in AlGaN/GaN Ultraviolet Photodetectors Using In Situ Heating

Abstract

Photodetectors based on the AlGaN/GaN heterostructure suffer from persistent photoconductivity (PPC) in which recovery from the optical stimulus can take days. This behavior is unsuitable for many applications where reliable and consistent optical response is required. This letter presents a method for suppressing PPC in AlGaN/GaN photodetectors by employing device suspension and in situ heating. The highly conductive two-dimensional electron gas (2DEG) at the interface of AlGaN and GaN serves as both a sensor and a heater (via Joule heating). Microfabricated AlGaN/GaN-on-Si ultraviolet (UV) photodetectors (suspended and unsuspended) were exposed to UV (365 nm) for 60 s and the transient responses were measured under various in situ heating conditions. The measured transient response showed a decay time of ~39 h when the photodetector was not heated and 24 s for a suspended photodetector with in situ 2DEG heating (270°C with a power of 75 mW). This remarkable suppression of the PPC in AlGaN/GaN UV photodetectors can be attributed to the novel device architecture and in situ heating capability, which enables acceleration of the carrier capture rate during operation.