Abstract:

The measurement of dislocation densities in heteroepitaxial semiconductor GaN film is important for the developement of blue light-emitting diodes, laser diode and high temperature, high-frequency electronic devices. As there is no matching substrate material, GaN thin films prepared by epitaxial growth often contain a large number of defects, most of which are edge dislocations. High resolution X-ray diffraction method and the mosaic model were used to measure and analyze the dislocation density of GaN film fabricated by metal organic chemical vapor deposition (MOCVD) on a 4H-SiC substrate with an AlGaN buffer layer. The crystal face tilting angle, in-plane twisting angle, grain size and crystal bending radius were investigated by symmetry and oblique symmetry diffraction methods. By eliminating the instrumental broadening width (mainly the incident beam divergence), grain size and wafer curvature influenced on the contribution to the full width at half maximum of rocking curves, Screw dislocation density and edge dislocation density of the GaN film were accurately determined to be 4.62×10⁷ cm^-2 and 5.20×10⁹ cm^-2, respectively. The total dislocation density was 5.25×10⁹ cm^-2. There were less than 1% screw dislocations, and the ratio of mixed to edge dislocation failed to be determined.

Key words: GaN film, high resolution X-ray diffraction, dislocation density