On the Scope of GaN-Based Avalanche Photodiodes for Various Ultraviolet-Based Applications

Abstract

We present a review of GaN avalanche photodiodes. GaN-based avalanche photodiodes are of emerging interest to the device community. The review covers various important aspects of the device such as the design space, substrate choice, edge termination efficacy, and last, but not least, the physics behind the avalanche breakdown in GaN. The study comprehends the reported impact ionization coefficients and how they may affect the device performances. Finally various reported GaN APDs are summarized and compared. We conclude that hole-initiated GaN APDs on free-standing GaN substrates can offer unprecedented advantages as ultraviolet light detectors, due to their ultra-high responsivity and low dark current.

Enhancing Linearity of Light Response in Avalanche Photodiodes by Suppressing Electrode Size Effect

“…This observation significantly enriches the theoretical framework regarding the nonlinearity of APDs. Additionally, in multi-junction structured APDs and certain specific configurations [ 25 ], similar charge accumulation phenomena may occur at the mesa’s edge, where differences in mesa size may cause local carrier accumulation, thereby affecting the device’s electrical characteristics.…”

Ultraviolet Photodetectors: From Photocathodes to Low-Dimensional Solids

“…Edge termination provides additional negative charges to terminate the electric field lines at the device boundary to reduce any localized peak electric field at each surface or corner. Figure 31 shows several edge terminations proposed for GaN APDs, including an edge termination based on ion implantation and etching and a field-based edge termination in which the field plate is connected to the anode electrode [62]. They effectively uniformize the electric field distribution, help reduce the dark current, and prevent the early breakdown of a device.…”

“…Figure 30. Avalanche photodiodes: (a) impact ionization process in a reverse-biased p-i-n junction; the separated absorption and multiplication (SAM) APD GaN structures: (b) based on GaN-onsapphire and the corresponding electric field distribution along the vertical direction; (c) the proposed SAM structure based on GaN-on-GaN and the corresponding electric field along the vertical direction.Adopted with permission from Ref [62]…”

The Effect of Nanopipes and an Inserted n‐AlGaN Interlayer on GaN Avalanche Photodiodes Performance

“…Gallium nitride (GaN) has the properties of a wide bandgap, high thermal conductivity, high breakdown voltage, high electron saturation velocity, high electron mobility, and strong radiation resistance, which makes it particularly suitable for applications requiring high temperatures and harsh environments. [1,2] Because of these advantages, GaN-based detectors have been extensively studied and one specific area of focus in GaN-based research is the development of ultraviolet (UV) detectors. UV detectors have a wide range of military and civil applications, such as missile warning, flame detection, medical imaging, sterilization, purification, and so on.…”

“…However, GaN films grown on conventional substrates like sapphire can lead to dislocation densities on the order of 10 8 cm −2 . [ 1 ] The high density of dislocations increases the leakage current, disrupts the electric field distribution, results in a premature breakdown, and limits the avalanche gain, all of which make it challenging to grow high‐performance GaN‐based APDs. [ 7 ] It is known that an excessive dark current affects the photo‐generated carrier multiplication process, which will significantly affect the sensitivity of light detection.…”