OPTICAL 3RD-HARMONIC INVESTIGATIONS OF GALLIUM NITRIDE NUCLEATION LAYERS ON SAPPHIRE

The magnitude of the chi(xxxx)((3)) element of the third-order optical susceptibility was measured in a series of wurtzite phase GaN nucleat ion layers (similar to 450 Angstrom) deposited on (00.1) sapphire at 5 40 degrees C and annealed to various temperatures up to 1050 degrees C . The nonlinear optical response exhibited a significant increase in f ilms that were annealed to temperatures in the range of 1015 to 1050 d egrees C. In addition, the correlation between the magnitude of chi(xx xx)((3)) with both the maximum value of the linear absorbance gradient and the residual homogeneous strain in the overlayer suggests that va riations in the crystalline content of the film and the bonding distan ce between the Ga and N atoms are primary factors in determining the t hird-order nonlinearity in GaN.