Effect of nucleation period on the physical properties of InN epilayers

The influence of structural and optoelectronic properties of InN epilayers on the duration of initial nucleation has been studied. High pressure chemical vapor deposition (HPCVD) has been utilized to deposit InN epilayers on GaN/sapphire (0001) templates at a reactor pressure of 15 bar. The initial nucleation period was varied between 10 s and 60 s, leaving all other growth parameters constant. The structural properties of the grown samples have been investigated by X-ray diffraction (XRD) spectroscopy and Raman spectroscopy. The optoelectronic properties were analyzed by Fourier transform infra-red (FTIR) spectroscopy. The layer thickness, free carrier concentration and void fraction were obtained by simulating IR spectra, using multi-layer stack model for epilayers and Lorentz-Drude model for dielectric function. Raman, X-ray diffraction (XRD) and void fraction calculation results suggest that the optimum nucleation time is between 10 - 20 s. However, simulation results revealed that the free carrier concentration of the bulk layer does not show any significant dependency on the duration of initial nucleation.