Annealing effects on polycrystalline GaN using nitrogen and ammonia ambients. (September 2016)

• Record Type: Journal Article
• Authors: Ariff, A.; Zainal, N.; Hassan, Z.
• Is Part Of: Superlattices and microstructures. Volume 97(2016)
• Page Start: 193
• Page End: 201
• Publication Date: 2016-09
• Subjects: Polycrystalline GaN -- m-plane substrate -- e-beam evaporator -- Post-annealing -- Ammonia; Superlattices as materials -- Periodicals; Microstructure -- Periodicals; Semiconductors -- Periodicals; Superréseaux -- Périodiques; Microstructure (Physique) -- Périodiques; Semiconducteurs -- Périodiques; 621.38152
• DOI: 10.1016/j.spmi.2016.05.005
• Languages: English
• ISSNs: 0749-6036

Abstract

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 (Ga2 O3 ) material. When the post-annealing treatment was carried out in N2 ambient at 650 °C, initial re-crystallization of the GaN grains was observed while the evidence of Ga2 O3 almost disappeared. As the NH3 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 N2 and NH3 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 N2 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. Highlights: Polycrystalline GaN was successfully grown by a combination of e-beam evaporator and post-annealing at optimum condition. Initial potential in producing improved polycrystalline GaN material in a simple and inexpensive manner is presented here. The formation of Ga2 O3 grains has been eliminated by the annealing at elevated temperature in NH3 ambient. The annealing in NH3 ambient at 950 °C has improved the crystal structure and luminescent properties of the GaN layer.