Mishra, Monu and Krishna, Shibin TC and Aggarwal, Neha and Vihari, Saket and Chauhan, Amit Kumar Singh and Gupta, Govind (2014) A Comparative Photoelectron Spectroscopic Analysis of MBE and MOCVD Grown Epitaxial GaN Films. Science of Advanced Materials, 6. pp. 1-6. ISSN 1947-2935

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The report presents X-Ray Photoelectron Spectroscopic analysis of as-received and cleaned MBE and MOCVD grown undoped epitaxial GaN films. We correlate observed changes in electronic structure and surface properties after employing a newly derived approach to clean GaN surfaces. The adopted approach is a combination of two different standard cleaning procedures consisting of ex-situ wet chemical (HCl) etching followed by an in-situ ultrahigh vacuum anneal (up to 750 °C), and successfully yielded a clean and stoichiometric GaN surface. The method was employed to investigate cleanliness of MBE and MOCVD grown GaN films and it was observed that major contaminants such as carbon and oxygen were significantly removed from the surface. XPS analysis revealed that MBE grown films show higher amount of surface contamination than the MOCVD grown films but can also be cleaned more efficiently. Thermal annealing (≥ 750 °C) resulted in the dissociation of GaN bonds and accumulation of metallic gallium on the surface on MOCVD grown GaN films, which was confirmed by core level as well as the valence band spectra. The n O/n N ratio of the films reduced drastically from 1.79 to 0.04 and 0.73 to 0.09 after cleaning with the stoichiometry (N:Ga) of 1.0 ± 0.04 and 1.1 ± 0.05 for MBE and MOCVD grown GaN films respectively. The VB maximum position of MBE and MOCVD grown films was observed to be shifted from 2.9 ± 0 eV to 2.2 ± 0.1 eV and 2.8 ± 0.1 eV to 1.4 ± 0.1 eV after cleaning of the surface.

Item Type: Article
Uncontrolled Keywords: GaN; MBE; MOCVD; XPS
Subjects: Materials Science
Applied Physics/Condensed Matter
Nanoscience/ Nanotechnology
Depositing User: Dr. Rajpal Walke
Date Deposited: 12 Sep 2016 05:31
Last Modified: 12 Sep 2016 05:31
URI: http://npl.csircentral.net/id/eprint/1693

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