Large-area solar-blind AlGaN-based MSM photodetectors with ultra-low dark current

Abstract

Large-area metal -semiconductor -metal (MSM) solar-blind photodetectors with a device area of 5 × 5 mm 2 have been fabricated on Al 0.4 Ga 0.6 N/AlN/sapphire epistructure. The photodetector exhibits ultra-low dark current density of 3.2 × 10 212 A/cm 2 under 20 V bias and a corresponding breakdown voltage of up to 385 V. The solar-blind/ultraviolet rejection ratio of the photodetector is more than four orders of magnitude with a maximum quantum efficiency of 28% at 275 nm.Introduction: Wide bandgap AlGaN-based materials are especially suitable for detecting ultraviolet (UV) radiation owing to their tunable bandgap (3.4 -6.2 eV), good thermal conductivity, excellent radiation hardness and high breakdown electric field. Solar-blind AlGaN-based UV photodetectors (PDs) with cutoff wavelength smaller than 280 nm have important potential applications, including missile plume sensing, chemical/biological agent detection, solar astronomy and covert space-to-space communications [1]. For many of these applications, capability of detecting very weak UV signals is often required. Thus, the PDs are desired to have both large detector area and low dark current, which are nevertheless hard to be realised simultaneously. In past studies, small-area AlGaN-based solar-blind PDs with low dark current density and high signal-to-noise ratio have been reported [2][3][4][5]. Although there are limited reports on AlGaN-based solar-blind Schottky PDs with active area of more than 1 mm 2 , those devices suffer from high leakage current owing to material quality or uniformity-related issues [6]. In this work, by growing the AlGaN active layer on a high-temperature (HT) AlN buffer layer on sapphire, we demonstrate a high-performance AlGaN-based metal -semiconductor -metal (MSM) PD with large device area of up to 25 mm 2 , which exhibits record low dark current density and high solar-blind/ultraviolet rejection ratio.

Recent Progress in Solar‐Blind Deep‐Ultraviolet Photodetectors Based on Inorganic Ultrawide Bandgap Semiconductors

“…In general, the Al x Ga 1− x N layers for MSM device application grow on sapphire substrates via MOCVD, MBE, sputtering method, and metal–organic vapor phase epitaxy (MOVPE) . In order to push forward with the growth of high‐quality Al x Ga 1− x N layers and also to promote the adhesion between the layers and substrates, GaN or AlN layers with thickness of tens to hundreds of nanometers were often employed as buffer or nucleation layers . It has been found that with the increase of x value, the peak response as well as the cutoff wavelengths of the MSM photodetectors manifested obvious blue transfer to shorter wavelength, an indicative of variation in the Al x Ga 1− x N bandgap.…”

Status and Outlook of Metal–Inorganic Semiconductor–Metal Photodetectors

“…prepared a large‐area AlGaN MSM‐PD of 5 × 5 mm 2 with the structure of Al 2 O 3 /AlN/Al 0.4 Ga 0.6 N/Ni/Au, which exhibited an ultralow dark current density of 3.2 × 10 −12 A cm −2 at 20 V bias, a UV–visible suppression ratio up to 10 4 , and a very high breakdown voltage. [ 89 ]…”

Enhanced quantum efficiency of AlGaN photodetectors by patterned growth

“…Commonly, the AlGaN detector structures are realized on sapphire substrates. The large lattice mismatch between the absorber layer and the substrate results in a high threading dislocation density (TDD) in the absorber, which enhances carrier recombination and reduces the detector responsivity . Several approaches to reduce the TDD, e.g., selective area epitaxy, growth on patterned sapphire substrates (PSS), and mask‐less epitaxial lateral overgrowth (ELO) have been reported.…”