Avalanche Gain in Metal–Semiconductor–Metal Ga₂O₃ Solar-Blind Photodiodes

Abstract

Metal–semiconductor–metal structured photodetectors based on β-Ga2O3 thin films were fabricated. Because of the high dark-resistance and considerable photoconduction, extremely uneven distribution of electric field is formed in the device under solar-blind UV light-illumination when a bias is added. Avalanche multiplication takes place in the high-field area near the electrode edges. Responsivity up to 46 A/W and the corresponding external quantum efficiency of 23 000% are observed. The photodetector shows a peak response at 248 nm, a sharp cut off edge at 262 nm (at −20 dB), and a fast response speed with a fall time of about 26.7 μs. Because of the ultralow response out of band, the rejection ratio R 254/365nm is larger than 7 orders of magnitude, where the illumination intensity at 254 and 365 nm are 0.5 and 1.2 mW/cm2, respectively.

A Strategic Review on Gallium Oxide Based Deep‐Ultraviolet Photodetectors: Recent Progress and Future Prospects

“…The increase in photocurrent mechanism in Ga 2 O 3 based devices is often attributed to either the carrier multiplication via impact ionization or to the presence of STHs which help in the lowering of the Schottky barrier height. [125][126] In the former case, a very high electric field region at the metalsemiconductor interface or the heterojunctions interface develops due to a space charge being formed. Once the illumination is switched on, the resistivity of gallium oxide drops because of the generation of electron-hole pairs.…”

Avalanche Effect and High External Quantum Efficiency in MgZnO/Au/ZnO Sandwich Structure Photodetector

“…For the 275 nm illumination, the photocurrent saturates at ≈20 V. With the increase in the bias beyond ≈63 V, the free carriers passing through the MgZnO-Au junction begin to get accelerated to high energy which can generate more charge carriers by ionization collisions. [13,14,29] The electric field between the interdigital electrodes is 2.1 × 10 5 V cm −1 . This current increase is the onset of avalanche behavior.…”

“…The research on avalanche effect has received extensive attention owing to its excellent low-light detection capability. [11][12][13][14] Under normal conditions, the avalanche effect is usually realized by p-n or p-i-n photodiodes because of the realization of collision ionization requiring absorption area, transition area, and multiplication area. Therefore, achievement of the avalanche effect in the MgZnO-based MSM PDs still faces many difficulties and challenges.…”

Current advances in solar-blind photodetection technology: using Ga2O3 and AlGaN

“…While testing the developed detection device, the photocurrent switching ratio of ∼10 8 with a dark current as low as 100 fA was acquired under a 20 V bias. Qiao et al 122 fabricated an SB UV detector based on a Ga 2 O 3 thin film, where an extremely high EQE of 23 000% was acquired due to the highly unbalanced distribution of the electric field, which caused avalanche multiplication in the device. Fig.…”

“…159,160 The MSM PDs based on thin films and nanostructures display an I light / I dark ratio surpassing 10 8 and reduced dark current in the range of ∼10 −13 –10 −9 A, while a specific detectivity and photoresponse rejection ratio ( R 254 / R 365 ) of 5.67 × 10 14 Jones, and 3.7 × 10 7 , respectively. 122,123,163…”