A route to low temperature growth of single crystal GaN on sapphire

Abstract

Gallium nitride (GaN) is considered one of most important semiconductor materials for the 21st century due to its combination of properties (high breakdown field, high electron saturation velocity and mobility, and good thermal conductivity) that make it suitable for high power, high frequency and high temperature applications. In this paper we demonstrate a possible route for the deposition of single crystal GaN on sapphire at 275 °C using plasma enhanced atomic layer deposition. TEM images and electron diffraction show that the first 5 nm of growth is epitaxial then transitions to 3D growth. The films have a preferential (002) growth direction, and a small in-plane and out-of-plane misorientation. The refractive index, extinction coefficient, and optical band gap are on par with those of GaN films grown at higher temperatures. The films are p-type with a carrier concentration of 1.68 × 10¹⁸ cm⁻³ and hole mobility of 110 cm² V⁻¹ s⁻¹.