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Epitaxial growth of semipolar AlxGa1-xN(1-103) films on ZnO substrates using room temperature buffer layer

Kohei Ueno 1Atsushi Kobayashi 1Jitsuo Ohta 1Hiroshi Fujioka 1,2

1. Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, Tokyo 153-8505, Japan
2. Core Research for Evolutional Science and Technology, Japan Science and Technology Agency (CREST-JST), Chiyoda-ku, Tokyo 102-0075, Japan

Abstract

   Group III nitride light emitting devices fabricated on semipolar planes have attracted increasing attention due to the potential for significant reduction in the undesirable effects of the built-in field. As the substrates for growth of high quality semipolar AlxGa1-xN films, ZnO is a promising candidate because ZnO has the same crystal structure and the small lattice mismatch with AlxGa1-xN. However, there still remains one serious problem with the use of the ZnO substrate, which is formation of the interfacial layers at the heterointerface that negate all the advantages of the nearly lattice-matched substrates. This problem stems from the high growth temperatures for AlxGa1-xN by the conventional growth techniques. Therefore, it can be solved by development of a low temperature growth technique for AlxGa1-xN . Recently, we have found that the use of pulsed laser deposition (PLD) leads to dramatic reduction in the growth temperature of nitrides.

   We have found that RHEED patterns during the growth of AlGaN on ZnO (1-103) at room temperature (RT) remain nearly unchanged from the initial stages, indicating the epitaxial growth of high quality AlxGa1-xN (1-103) on this substrate. X-ray reflectivity measurements have revealed that the heterointerface between Al x Ga 1-x N and ZnO is atomically abrupt. This result indicates that the reduction in growth temperature down to RT is inherently important for suppression of the interfacial reactions. Figure 1 shows XRD 2θ/ω curves of AlxGa1-xN with various x values grown at 850°C on the RT AlGaN layers. One can clearly see 1-103 diffraction for all the samples, indicating that high quality semipolar AlGaN can be grown at all the Al concentrations with this technique. We also found the small tilt of the [1-103]AlGaN relative to that of ZnO from reciprocal space map near 1-103 diffraction shown in Fig. 2. This phenomenon can be attributed to the formation of the small tilt angle boundary at the heterointerface.

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Related papers

Presentation: Poster at E-MRS Fall Meeting 2009, Symposium C, by Kohei Ueno
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-07 14:20
Revised:   2009-06-07 00:48