Effects of thermal annealing on the morphology of the AlxGa(1−x)N films

Abstract

Effects of thermal annealing on the morphology of the Al x Ga (1 À x) N films with two different high Al-contents (x =0.43 and 0.52) have been investigated by atomic force microscopy (AFM). The annealing treatments were performed in a nitrogen (N 2) gas ambient as short-time (4 min) and long-time (30 min). Firstly, the films were annealed as short-time in the range of 800-950 1C in steps of 50-100 1C. The surface root-meansquare (rms) roughness of the films reduced with increasing temperature at short-time annealing (up to 900 1C), while their surface morphologies were not changed. At the same time, the degradation appeared on the surface of the film with lower Al-content after 950 1C. Secondly, the Al 0.43 Ga 0.57 N film was annealed as long-time in the range of 1000-1200 1C in steps of 50 1C. The surface morphology and rms roughness of the film with increasing temperature up to 1150 1C did not significantly change. Above those temperatures, the surface morphology changed from step-flow to grain-like and the rms roughness significantly increased.

On the profile of frequency dependent dielectric properties of (Ni/Au)/GaN/Al0.3Ga0.7N heterostructures

“…Reliability, performance and life time combination of these devices are much higher than other devices. However, in order to improve the performance of these devices; the effects of surface passivation, dielectric layer (Al 2 O 3 , Si 3 N 4 ) insertion, surface treatments with chemical or plasma have been investigated [11][12][13][14][15][16][17][18][19]. However, it still difficult to obtain a high quality GaN epilayer because of the large lattice mismatch and large difference in the thermal expansion coefficients between the GaN film, sapphire, and SiC substrate.…”

“…However, it still difficult to obtain a high quality GaN epilayer because of the large lattice mismatch and large difference in the thermal expansion coefficients between the GaN film, sapphire, and SiC substrate. This fact causes threading dislocation density (DD) and interface states (N ss ) generation, as grown by metal-organic chemical vapor deposition (MOCVD) in the GaN layer [13][14][15][16][17][18][19]. The reason for the existence of DD and N ss is the interruption of the periodic lattice structure at the surface, surface preparation, impurity concentration of semiconductor and the formation of barrier high at M/S interface [20][21][22].…”

Structural investigation and electronic band transitions of nanostructured TiO2 thin films

“…With respect to these results, it can be said that the defect concentration in the lattice is decreased with increasing the annealing temperature. Thermal annealing has a strong impact on surface morphology of the thin films [14,26]. In the present study, surface morphology of the annealed-TiO 2 films was characterized by AFM technique.…”

Optimization of visible photoluminescence emission from Ni-Zn ferrite thin films

“…Moreover, the effect of annealing temperature is mainly on the crystallite size which should increase by annealing, i.e. the smoothing of the samples will increase which is the reason of the slight reduction of root mean square [40,41].…”