Surface and Interface Properties of Metal-Organic Chemical Vapor Deposition Grown a-Plane MgxZn1-xO (0 <= x <= 0.3) Films

G. Saraf, J. Zhong, O. Dulub, U. Diebold, T. Siegrist, Y. Lu

Department of Electrical and Computer Engineering, Rutgers University, Piscataway, New Jersey 08854, U.S.A.
Department of Physics, Tulane University, New Orleans, Louisiana 70118, U.S.A.
Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974, U.S.A.

J. Electron. Mater. 36 (2007) 446-451

The a-plane MgxZn1-xO (0 <= x <= 0.3) films were grown on r-plane (0 1 -1 2) sapphire substrates using metal-organic chemical vapor deposition (MOCVD). Growth was done at temperatures from 450 °C to 500 °C, with a typical growth rate of ~500 nm/h. Field emission scanning electron microscopy (FESEM) images show that the films are smooth and dense. X-ray diffraction (XRD) scans confirm good crystallinity of the films. The interface of MgxZn1-xO films with r-sapphire was found to be semicoherent as characterized by high-resolution transmission electron microscopy (HRTEM). The MgxZn1-xO surfaces were characterized using scanning tunneling microscopy (STM) in ultrahigh vacuum (UHV). Low-energy electron diffraction (LEED) shows well-ordered and single-crystalline surfaces. The films have a characteristic wavelike surface morphology with needle-shaped domains running predominantly along the crystallographic c-direction. Photoluminescence (PL) measurements show a strong near-band-edge emission without observable deep level emission, indicating a low defect concentration. In-plane optical anisotropic transmission was observed by polarized transmission measurements.

Reprints available from U. Diebold (diebold at iap_tuwien_ac_at).

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