Infrared reflectance of GaN films grown on Si(001) substrates

GaN thin films on Si(001) substrates are studied by infrared reflectance (I RR) spectroscopy at room temperature (RT). Variations in the IRR spectral l ine shape with the microstructure of GaN/Si(011) film are quantitatively ex plained in terms of a three-component effective medium model. In this model , the nominally undoped GaN film is considered to consist of three elementa ry components, i.e., single crystalline GaN grains, pores (voids), and inte r-granulated materials (amorphous GaN clusters). Such a polycrystalline nat ure of the GaN/Si(001) films was confirmed by scanning electron microscopy measurements. It was demonstrated that based on the proposed three-componen t effective medium model, excellent overall simulation of the RT-IRR spectr a can be achieved, and the fine structures of the GaN reststrahlen band in the measured RT-IRR spectra can also be interpreted very well. Furthermore, the volume fraction for each component in the GaN/Si(001) film was accurat ely determined by fitting the experimental RT-IRR spectra with the theoreti cal simulation. These results indicate that IRR spectroscopy can offer a se nsitive and convenient tool to probe the microstructure of GaN films grown on silicon. (C) 2001 American Institute of Physics.