UV Photodetector Based on Mg-Doped GaN Thin Films Prepared by Sol-Gel Spin Coating

Abstract

In this work, sol-gel spin coated of magnesium (Mg) doped gallium nitride (GaN) thin films grown on AlN sapphire substrate was reported. The structural, lattice vibrational, and electrical properties of the deposited films were investigated and compared. X-ray diffraction results show that the deposited films composed of wurtzite structure with preferred orientation of GaN(002). The Raman active phonon modes correspond to the E2(high) and A1(LO) at 568 cm-1 and 733 cm-1 phonon modes of the hexagonal GaN were observed, while a broad peak attributed to the Mg-related lattice vibrational mode was detected at 669 cm-1. The Raman phonon modes were detected by using Raman spectroscopy. Hall effects results show that the resistivity, carrier concentration, and hall mobility of the Mg-doped GaN film was 0.1397 Ω cm, 1.77 × 1018 cm3, and 6.04 cm2/Vs, respectively. Besides, the characteristics of the ultraviolet (UV) photoresponse of the fabricated detector were investigated. The current-voltage characteristics of the Mg-doped GaN UV photodetector exhibits Schottky behaviour. The current-voltage measurements were carried out at room temperature with a computer-controlled integrated Source Meter (Keithley 2400). Lastly, the ideality factor and Schottky barrier heights were calculated using thermionic emission theory.