Gain mechanism and carrier transport in high responsivity AlGaN-based solar blind metal semiconductor metal photodetectors

Abstract

We report on the highest responsivity for III-nitride Metal Semiconductor Metal solar-blind photodetectors on sapphire. Devices on unintentionally doped AlGaN epilayers grown by Metal Organic Chemical Vapor Deposition exhibited sharp absorption cut-off in the range of 245–290 nm. Very high responsivity >5 A/W at 10 V bias was achieved with visible rejection exceeding three orders of magnitude for front illumination. Compared to the responsivity values reported in the literature for state-of-the-art solar-blind photodetectors, this work presents the highest values of responsivity at a given bias and up to sub-250 nm detection threshold. The high responsivity is attributed to an internal gain mechanism operating on these devices. The reverse-bias leakage current across these samples was found to be dominated by thermionic field emission at low biases and Poole-Frenkel emission from a deep trap level (0.7 eV from the conduction band-edge for Al0.50Ga0.50 N) at high biases.

Microwave irradiation-assisted deposition of Ga2O3 on III-nitrides for deep-UV opto-electronics

“…As the M-S junction has to maintain charge neutrality, more electrons have to flow from the metal side, subsequently lowering the Schottky barrier, thereby leading to gain in the PD. A similar phenomenon has been reported in GaN, AlGaN, and β-Ga2O3 MSM-based PDs earlier 15, [41][42][43] .…”

Gate-controlled amplifiable ultraviolet AlGaN/GaN high-electron-mobility phototransistor

“…Since the 10 nm thick AlGaN barrier has a relatively lower 2-DEG than the 30 nm thick AlGaN barrier, the photogenerated carrier can easily exceed 2-DEG in the 10 nm thick AlGaN barrier, resulting in a fast rising time of photocurrent. In addition, the higher Al composition and thicker AlGaN barrier grown on GaN channel layer may have more crystal defects forming impurity-related deep levels such as misfit dislocations and point defects that can play a role in absorbing UV ligth at the top AlGaN barrier 36 . As a result, these crystal defects can delay the formation of the photogenerated carriers in the AlGaN barrier and the GaN channel layer, resulting in a low response time of the AlGaN/GaN HEMT with a 30 nm thick AlGaN barrier layer.…”

Light based underwater wireless communications

“…Table II summarizes the performance of semiconductor based solar-blind PDs. 88,[96][97][98][99][100][101][102][103][104][105][106][107][108][109][110][111][112][113] The table is ordered by the use of different groups of materials. As indicated in the table, III-nitride based PDs are among the first and ideal choices for high efficiency and high-speed devices.…”

“…The direct bandgap AlGaN material is tunable from its binary alloy from 3.4 eV (GaN) to 6.2 eV (AlN) at room temperature enables the wide spectrum coverage from blue to UVC. [97][98][99][100][101]114,115) The past 20 years have witnessed the improvement in AlGaN based PDs with different device configurations of metalsemiconductor-metal (MSM), PN heterostructure, PIN, and Schottky diodes. 90,94) The bandwidth can reach GHz range.…”