Nonpolar a-plane GaN grown on r-plane sapphire using multilayer AlN buffer by metalorganic chemical vapor deposition

C. H. Chiang, K. M. Chen, Y. H. Wu, Y. S. Yeh, Wei-I Lee, Jenn-Fang Chen, K. L. Lin, Y. L. Hsiao, W. C. Huang, Edward Yi Chang

Research output: Contribution to journalReview article

18 Scopus citations

Abstract

Mirror-like and pit-free non-polar a-plane (1 1 -2 0) GaN films are grown on r-plane (1 -1 0 2) sapphire substrates using metalorganic chemical vapor deposition (MOCVD) with multilayer high-low-high temperature AlN buffer layers. The buffer layer structure and film quality are essential to the growth of a flat, crack-free and pit-free a-plane GaN film. The multilayer AlN buffer structure includes a thin low-temperature-deposited AlN (LT-AlN) layer inserted into the high-temperature-deposited AlN (HT-AlN) layer. The results demonstrate that the multilayer AlN buffer structure can improve the surface morphology of the upper a-plane GaN film. The grown multilayer AlN buffer structure reduced the tensile stress on the AlN buffer layers and increased the compressive stress on the a-plane GaN film. The multilayer AlN buffer structure markedly improves the surface morphology of the a-plane GaN film, as revealed by scanning electron microscopy. The effects of various growth V/III ratios was investigated to obtain a-plane GaN films with better surface morphology. The mean roughness of the surface was 1.02 nm, as revealed by atomic force microscopy. Accordingly, the multilayer AlN buffer structure improves the surface morphology and facilitates the complete coalescence of the a-plane GaN layer.

Original languageEnglish
Pages (from-to)2415-2418
Number of pages4
JournalApplied Surface Science
Volume257
Issue number7
DOIs
StatePublished - 1 Jan 2011

Keywords

  • Crystal morphology
  • GaN
  • MOCVD
  • Nonpolar

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