Impact of Carrier Gas on the GaN Layers Properties Grown on (001) and (11n) GaAs Substrates by AP-MOVPE: Comparative Study

Abstract

The impact of carrier gas on the GaN layers properties grown by atmospheric pressure metal-organic vapor-phase epitaxy (AP-MOVPE) on (001) and (11n) GaAs substrates were investigated. The Arrhenius plots of growth rate deduced from laser reflectometry measurements give an activation energy of Ea1 = 0.045 eV when the H2 was used as the carrier gas. In the case of using N2 as the carrier gas, the results give Ea2 = 0.081 eV as a value of activation energy, which is approximately 2 times greater than Ea1. Scanning electron microscopy results show that when N2 is used, the resulting material quality is low, but the use of H2 is successful to prevent the cracking of GaN layers and results in improvement of crystalline properties. From the X-ray diffraction result, we conclude that both (001) and (113) GaAs substrate orientations as well as the use of H2 as the carrier gas favors the GaN growth with cubic structure, whereas the GaN hexagonal structure is favored for growth on (112) and (111) GaAs substrates orientations with N2. Cathodoluminescence measurements show that a mechanism of phase transformation occurs when the growth temperature rise from 800 to 900°C.