Abstract
We deposited 300-nm-thick GaN films on an amorphous glass substrate at a substrate temperature of 300 °C by using pulsed direct current (DC) sputtering. A ZnO buffer layer was utilized to improve the crystalline quality of the GaN films. Scanning electron microscopy results showed that the GaN thin films were grown along the c-axis and possessed a columnar structure. Atomic force microscopy results revealed that the GaN film deposited at a sputtering power of 75 W had the maximum grain size (24.1 nm). Room-temperature photoluminescence measurement of the GaN films indicated an ultraviolet near-band-edge emission at 365 nm and a Zn impurity energy transition level at 430 nm. In addition, X-ray diffraction conducted on the GaN films revealed a predominant (002) hexagonal wurtzite structure. The GaN film deposited at the sputtering power of 75 W demonstrated a high optical transmittance level of 88.5% in the wavelength range of 400–1100 nm. The material characteristics of the GaN films and ZnO buffer layer were studied using cross-sectional high-resolution transmission electron microscopy. The deposition of GaN films by using pulsed DC magnetron sputtering can result in high material quality and has high potential for realizing GaN-related optoelectronic devices on glass substrates.
Highlights
Gallium nitride (GaN) films have a wide energy band gap along with inherent advantages of chemical and thermal stability, hardness, high thermal conductivity, high breakdown voltage, and electron mobility [1]
The X-ray diffraction (XRD) FWHM value is a vital parameter for assessing the average crystallite size according to the Scherrer formula [24,25]: The GaN films deposited on an amorphous glass substrate in this study demonstrated clear and narrow XRD FWHM values because of the superior crystal quality and optimal structural properties provided by the zinc oxide (ZnO) buffer layer, which contributed to the grain growth of the GaN films [19]
This study investigated the sputtering deposition of high-quality GaN films with a ZnO buffer layer on an amorphous glass substrate by using pulsed direct current (DC) sputtering
Summary
Gallium nitride (GaN) films have a wide energy band gap along with inherent advantages of chemical and thermal stability, hardness, high thermal conductivity, high breakdown voltage, and electron mobility [1]. Such films have high potential for application in high-quality optoelectronic devices such as light-emitting diodes; in addition, they can be applied in other electronic devices such as field-effect transistors, heterojunction bipolar transistors, and high-electron mobility transistors [2,3]. For high-temperature operations and high-power electronic applications, GaN films and their related compound materials are relatively favorable because of their wide energy band gap and excellent thermal stability. A large lattice mismatch of 15% exists between a sapphire substrate and a GaN
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