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

Lalit Goswami,Jahangeer Ahmed,Pargam Vashishtha,Rajeshwari Pandey,Govind Gupta,M A Majeed Khan,Shubhendra Kumar Jain,Neha Aggarwal,Shruti Nirantar

doi:10.1038/s41598-021-90450-w

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.

Highlights

Gallium nitride (GaN) ultraviolet (UV) photodetectors (PDs) attracted a lot of attention due to their versatility and ability to serve in an extreme environment
We report the utilization of AlN buffer layer (800 °C) for growth of less strained and stress relaxed, higher aspect ratio hexagonally stacked GaN-nanocolumnar structures i.e. nanotowers (GaN-NTs) on Si (111) substrate via plasma assisted molecular beam epitaxy (PAMBE) system
The growth of GaN-NT structure is carried out on reconstructed Si (111) 7 × 7 surface and in-situ monitored by reflection high electron diffraction (RHEED) technique.The crystallinity of grown structure was evaluated by High-Resolution X-ray Diffraction (HRXRD) 2θ–ω scan and its peak positions were utilized to calculate the strain via lattice constant estimation using Bragg’s law[22]

Summary

Introduction

Gallium nitride (GaN) ultraviolet (UV) photodetectors (PDs) attracted a lot of attention due to their versatility and ability to serve in an extreme environment.

Results

Conclusion