Annealing effects on polycrystalline GaN using nitrogen and ammonia ambients

Abstract This paper describes effects of using post-annealing treatment in different conditions on the properties of polycrystalline GaN layer grown on m -plane sapphire substrate by electron beam (e-beam) evaporator. Without annealing, GaN surface was found to have a low RMS roughness with agglomeration of GaN grains in a specific direction and the sample consisted of gallium oxide (Ga 2 O 3 ) material. When the post-annealing treatment was carried out in N 2 ambient at 650 °C, initial re-crystallization of the GaN grains was observed while the evidence of Ga 2 O 3 almost disappeared. As the NH 3 annealing was conducted at 950 °C, more effect of re-crystallization occurred but with less grains coalescence. Three dominant XRD peaks of GaN in ( 10 1 ¯ 0 ) , (0002) and ( 10 1 ¯ 1 ) orientations were evident. Near band edge (NBE) related emission in GaN was also observed. The significant improvement was attributed to simultaneous recrystallization and effective reduction of N deficiency density. The post-annealing in a mixture of N 2 and NH 3 ambient at 950 °C was also conducted, but has limited the effectiveness of the N atoms to incorporate on the GaN layer due to ‘clouding’ effect by the inert N 2 gas. Further increase in the annealing temperature at 980 °C and 1100 °C, respectively caused severe deteriorations of the structural and optical properties of the GaN layer. Overall, this work demonstrated initial potential in improving polycrystalline GaN material in simple and inexpensive manner.