Atomic force microscopy analysis of morphology of the upper boundaries of GaN thin films prepared by MOCVD

In this paper the results of the atomic force microscopy analysis of the upper boundaries of the GaN nucleation and buffer films prepared by MOCVD are presented. It is shown that the upper boundaries of nucleation films exhibit morphology identical with statistical roughness. The values of the basic statistical roughness quantities, i.e. the RMS values of the heights and the autocorrelation length values, of these boundaries are determined in dependences on time and temperature of their annealing. These RMS values decrease with increasing values of both technological parameters. It is also found that the corresponding power spectral density functions of the upper boundaries of these films satisfy the Gaussian function very well. Furthermore, it is shown that the GaN buffer films created onto the selected nucleation film have the upper boundaries whose morphology is different from the typical statistical surface roughness. Both RMS values and autocorrelation length values decrease with increasing buffer film thickness and the power spectral density function of these films is rather different from the Gaussian function. It is shown that a correlation between the upper boundaries of the buffer films and the nucleation films is relatively weak.