Chemical solution deposited GaN films from oxygen- and nitrogen-based precursors

Abstract

GaN films were produced by the chemical solution deposition method (CSD) using two different precursors—gallium dimethyl amide (GDA; containing gallium–nitrogen bonds) and gallium isopropoxide (GIP; containing gallium–oxygen bonds). Pyrolysis of the GDA film at 600 °C produced a continuous layer of GaN grains with a single orientational relation with the substrate [GaN (0001) ∥ Al₂O₃ (0001) and GaN (1010) ∥ Al₂O₃ (1120)], and an overlying polycrystalline film. At temperatures greater than 600 °C, the oriented grains consumed the polycrystalline layer via an evaporation–condensation mass transport. Pyrolysis of the GIP films at 600 °C produced a continuous layer of gallium oxynitride having the corundum structure [i.e., α–Ga₂O_(3−x)N_2/3x] with an epitaxial relation to the substrate (α–Ga₂O_(3−x)N_2/3x[0001] ∥ Al₂O₃ [0001] and α–Ga₂O_(3−x)N_2/3x [1010] ∥ Al₂O₃ [1120]), and an overlaying polycrystalline gallium oxynitride film with a spinel structure. Increasing temperature caused growth of oriented grains in contact with the substrate and conversion of the oxynitride to wurtzite GaN at 800 °C. Room-temperature (300 K) and low-temperature(77 K) photoluminescence measurements behaved similarly to metal-organic chemical vapor deposition based GaN with additional photoluminescence most likely due to nitrogen vacancy impurities.