Mishra, Monu and Krishna, T. C. Shibin and Aggarwal, Neha and Gupta, Govind (2015) Surface chemistry and electronic structure of nonpolar and polar GaN films. Applied Surface Science, 345. 440-447 . ISSN 0169-4332

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Abstract

Photoemission and microscopic analysis of nonpolar (a-GaN/r-Sapphire) and polar (c-GaN/c-Sapphire) epitaxial gallium nitride (GaN) films grown via RF-Molecular Beam Epitaxy is reported. The effect of polarization on surface properties like surface states, electronic structure, chemical bonding and morphology has been investigated and correlated. It was observed that polarization lead to shifts in core level (CL) as well as valence band (VB) spectra. Angle dependent X-ray Photoelectron Spectroscopic analysis revealed higher surface oxide in polar GaN film compared to nonpolar GaN film. On varying the take off angle (TOA) from 0 degrees to 60 degrees, the Ga-O/Ga-N ratio varied from 0.11-0.23 for nonpolar and 0.17-0.36 for polar GaN film. The nonpolar film exhibited N-face polarity while Ga-face polarity was perceived in polar GaN film due to the inherent polarization effect. Polarization charge compensated surface states were observed on the polar GaN film and resulted in downward band bending. Ultraviolet photoelectron spectroscopic measurements revealed electron affinity and ionization energy of 3.4 +/- 0.1 eV and 6.8 +/- 0.1 eV for nonpolar GaN film and 3.8 +/- 0.1 eV and 7.2 +/- 0.1 eV for polar GaN film respectively. Field Emission Scanning Electron Microscopy measurements divulged smooth morphology with pits on polar GaN film. The nonpolar film on the other hand showed pyramidal structures having facets all over the surface.

Item Type:	Article
Uncontrolled Keywords:	GaN Photoemission Polarization Surface states
Subjects:	Chemistry > Physical Chemistry Materials Science Applied Physics/Condensed Matter
Divisions:	UNSPECIFIED
Depositing User:	Dr. Rajpal Walke
Date Deposited:	21 Oct 2016 05:30
Last Modified:	21 Oct 2016 05:30
URI:	http://npl.csircentral.net/id/eprint/2021

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