Growth of GaN Using Lithium Flux at Super-Atmospheric Pressures

Abstract

Gallium nitride (GaN) is a wide-bandgap semiconductor with excellent electrical and optical properties, making it a leading candidate for next-generation power electronic devices and optoelectronic devices. The widespread adoption of GaN in high-power applications is hindered by the lack of inexpensive, large-area, high-quality single crystals for substrates. In this work, we demonstrate the growth of GaN single crystals from a lithium (Li)-flux at temperatures and nitrogen pressures up to 935 °C and 10 MPa, respectively, expanding the previously reported growth window by approximately 130 °C and a 35-fold increase in pressure. Through systematic systematically increasing synthesis temperature at elevated pressures, we identify parameters that influence crystal morphology and quality. Spontaneously nucleated, single crystals grown from the melt achieved sizes up to 3 mm in 100 h, with best growth conditions achieved at 935 °C, ∼ 8 MPa N₂ pressure and a 2.4 Ga/Li₃N ratio. Characterization of the grown crystals demonstrates promising structural properties consistent with high-purity, low-defect, chemically and phase-pure wurtzite GaN with an ω-rocking curve full width at half maximum of 87 arcsec.