Organic passivation of Al_0.5Ga_0.5N epilayers using self-assembled monolayer of Zn(II) porphyrin for improved solar-blind photodetector performance

Abstract

We report on the passivation of surface states of Al0.5Ga0.5N epilayers by employing self-assembled monolayers (SAM) of organic molecules, which led to a significant improvement in the performance of Al0.5Ga0.5N based solar-blind photodetector. The formation of SAM of meso-(5-hydroxyphenyl)-10,15,20-tri(p-tolyl) porphyrin (ZnTPP(OH)) on the surface of Al0.5Ga0.5N was probed by contact angle measurement (CA), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The successful passivation of surface states was confirmed by Kelvin probe force microscopy (KPFM) as a significant decrease in the surface potential of Al0.5Ga0.5N by ~280 mV was observed. The inference was supported by a four-fold increase in the photoluminescence (PL) intensity of the near-band edge emission (NBE) peak upon passivation. As a result, the dark current of the as-fabricated solar-blind photodetector reduced by 2 orders of magnitude, without compromising with the magnitude of the photo current at 270 nm. The role of SAM was evident in improving the performance of the photodetector as the peak value of photo-to-dark current ratio (PDCR) enhanced by ~36 times. The peak responsivity of the photodetector increased from 1.6 to 2.2 mA/W at 10 V. The significant reduction in the dark current and enhancement in the responsivity led to an improvement in the specific detectivity by ~10 times. Additionally, the response speed of the photodetector was found to improve significantly from 4 to 0.5 s.

Deep-Ultraviolet Photodetectors Based on Hexagonal Boron Nitride Nanosheets Enhanced by Localized Surface Plasmon Resonance in Al Nanoparticles

“…To investigate the wavelength selectivity of the PDs, the response of the devices was studied by varying the incident wavelength over a broad range from 700 nm (visible) to 200 nm (deep UV). The responsivity is an important performance parameter of the PD and is mathematically given by , where P λ is the incident optical power corresponding to the wavelength λ. As shown in the inset of Figure b, all of the PDs were not responsive from 700 nm (visible) to 260 nm (UV).…”

“…To investigate the wavelength selectivity of the PDs, the response of the devices was studied by varying the incident wavelength over a broad range from 700 nm (visible) to 200 nm (deep UV). The responsivity is an important performance parameter of the PD and is mathematically given by 44,45 = −…”

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

“…The device exhibited an even higher EQE of 28% under 10 V bias together with a highly suppressed dark current value of <0.2 pA at a higher bias of 20 V. Here, the high temperature AlN buffer plays an important role of high energy barrier, restricting the lateral flow of the leakage current in the device, which resulted in an ultra-low dark current density and a high performance large-area PD. In a recent work, Kaushik et al 52 investigated a surface passivation method, where the performance of an SB PD was further improved by employing self-assembled monolayers of organic molecules on the surface of an Al 0.5 Ga 0.5 N-based device structure. This surface passivated device yielded a significant reduction in the dark current, which led to ∼10 times improvement in its specific detectivity, hence improving the overall performance of the SB UVPD.…”

A GaSe/Si-based vertical 2D/3D heterojunction for high-performance self-driven photodetectors

“…Moreover, the GaSe akes were mechanically exfoliated, and it has been reported that akes obtained by mechanical exfoliation are prone to edge defects, which serve as traps to the photogenerated electron-hole pairs and reduce the overall speed of the fabricated device. 36,54,55 We further carried out KPFM measurements on the vertical GaSe/Si p-n heterostructure to understand its band alignment. KPFM is one of the electrical modes of AFM; it is used to obtain workfunction values and information regarding the surface potential and charge at the nanoscale.…”