Fabrication of GaN nano-towers based self-powered UV photodetector

Abstract

The fabrication of unique taper-ended GaN-Nanotowers structure based highly efficient ultraviolet photodetector is demonstrated. Hexagonally stacked, single crystalline GaN nanocolumnar structure (nanotowers) grown on AlN buffer layer exhibits higher photocurrent generation due to high quality nanotowers morphology and increased surface/volume ratio which significantly enhances its responsivity upon ultraviolet exposure leading to outstanding performance from the developed detection device. The fabricated detector display low dark current (~ 12 nA), high ILight/IDark ratio (> 104), fast time-correlated transient response (~ 433 µs) upon ultraviolet (325 nm) illumination. A high photoresponsivity of 2.47 A/W is achieved in self-powered mode of operation. The reason behind such high performance could be attributed to built-in electric field developed from a difference in Schottky barrier heights will be discussed in detail. While in photoconductive mode, the responsivity is observed to be 35.4 A/W @ − 3 V along with very high external quantum efficiency (~ 104%), lower noise equivalent power (~ 10–13 WHz−1/2) and excellent UV–Vis selectivity. Nanotower structure with lower strain and dislocations as well as reduced trap states cumulatively contributed to augmented performance from the device. The utilization of these GaN-Nanotower structures can potentially be useful towards the fabrication of energy-efficient ultraviolet photodetectors.

Surface-dependent band structure variations and bond deviations of GaN

“…Although the {10% 11} faces are less common, tapered GaN nanotowers expose such surfaces. 38 Because the slab structures for tunable plane layers do not simply repeat with each additional layer, varying the plane number yields dissimilar band structures and hence DOS diagrams. Alternating band gap values are also observed.…”

Ultrafast and Highly Stable Photodetectors Based on p-GeSe/n-ReSe2 Heterostructures

“…To confirm the n-type carriers in the ReSe 2 device, the transfer characteristics with Sc/Au contact were measured at V ds of 1.0 V (Figure 2b). A high value of the current I on /I off ratio (>10 5 ) is observed. The conceived values of electrons mobility are 96, 79, 67, and 39 cm 2 /Vs with Sc/Au, Al/Au, Ti/Au, and Pt/Au, respectively (Figure S6a).…”

“…Photodetection in the near-infrared (NIR) region is invaluable for upcoming remote sensing, imaging, biomedical optics and images, spectroscopy, optical communication, and space communication applications. − Commercially available, metal-oxide-semiconductor (MOS)-based photodetectors have gained noteworthy consideration of industry over the past few decades. Light of different wavelengths is detected by using different photoactive semiconductors such as Si (400–1100 nm), InGaAs (800–1600 nm), Hg 1– x Cd x Te (2–5.5 μm), and GaN (<400 nm). − Some of them show extraordinary performance but require intricate fabrication process, growth at high temperature, and low and high temperature for operation with expensive facilities …”

Advances in Self-Powered Ultraviolet Photodetectors Based on P-N Heterojunction Low-Dimensional Nanostructures

“…In recent years, biological and medical research has shown the very important role of the UV-A (400–320 nm) and UV-B (320–280 nm) bands on the Earth’s biosystem and human health (erythema, eye cataracts, skin cancer, etc.). Thus, it is of great research value to develop wide-bandgap semiconductor photodetectors tailored to the various solar UV bands and blind to the visible and IR emissions [ 89 , 90 ]. Although a variety of semiconductor photodetectors are able to respond to UV photons, it has been recognized that GaN-based photodetectors are excellent candidates for the detection of UV radiation, and moreover, AlGaN-based photodetectors with threshold energies of 3.4 eV (GaN) up to 6.2 eV (AlN) can be fabricated by a proper choice of the Al mole fraction, which provides a good opportunity for deep UV detection [ 91 , 92 , 93 , 94 ].…”