Review of polarity determination and control of GaN


M. Sumiya
Shizuoka Univeristy
and
CREST-JST

S. Fuke
Shizuoka Univeristy

This article was received on Friday, November 21, 2003 and accepted on Monday, February 9, 2004.

Abstract

Polarity issues affecting III-V nitride semiconductors are reviewed with respect to their determination and control. A set of conditions crucial to the polarity control of GaN is provided for each of the following growth techniques; molecular beam epitaxy (MBE), pulsed laser deposition (PLD) and hydride vapor phase epitaxy (HVPE). Although GaN films might have been deposited by identical growth methods using the same buffer layer technologies, there is often a conflict between the resulting polarities achieved by different research groups. In this paper, we present the implications of the conditions used in each of the processes used for two-step metalorganic chemical vapor deposition (MOCVD), demonstrating systematic control of the polarity of GaN films on sapphire substrates. The potential for confusion in polarity control will be explained, taking into account the implications clarified in our studies. The correlation between the polarity and the growth conditions will be discussed in order to provide a mechanism for the determination and control of the crystal polarity during the growth of GaN films.

Outline

  • Introduction
  • Characterization of GaN polarity
  • Notation of GaN polarity
  • Spontaneous polarization of nitride semiconductor material
  • History of polarity evaluation
  • 1984-1994: XPS and thermal stability
  • 1996: CBED
  • 1997-1998: Surface reconstruction, chemical stability and CAICISS
  • Recent movements
  • Polarity characterization by CAICISS
  • Principle and advantages
  • Application of CAICISS to an InGaN SQW
  • Management of polarity in MBE, PLD, and HVPE-GaN
  • MBE
  • Conditions used for treatment of the sapphire and for the buffer layer
  • Substrate nitridation
  • Conditions used for AlN and GaN buffer layers
  • Insertion of a metal layer
  • Mg accumulation layer
  • Deposition of GaN film: V/III ratio and growth rate
  • Factors for controlling the polarity in MBE-GaN on sapphire substrate
  • PLD
  • HVPE
  • Until 1992: Direct growth, GaCl treatment, and ZnO insertion
  • 1997-1999: AlN and GaN buffer layers
  • 2000-2003: Kinetic effect and a new approach
  • Features for controlling polarity in HVPE-GaN
  • Polarity management in MOCVD-GaN
  • Previous work
  • Our sample conditions in MOCVD
  • Substrate treatment and GaN buffer layer
  • Article 1: Surface of the treated sapphire substrate
  • Article 2: Structure of the LT-GaN buffer layer on the nitrided sapphire substrate
  • Article 3: Interface between the GaN buffer and the treated sapphire substrate
  • Recipe 1: Thickness and annealing of the GaN buffer layer on nitrided substrates
  • Thickness
  • V/III ratio
  • Annealing conditions for the buffer layer
  • Recipe 2: Growth on H2 cleaned substrates
  • AlN buffer layer
  • Article 4: Comparison with LT-GaN buffer layers
  • Recipe 3: High-temperature AlN buffer layers
  • Polarity of the HT-GaN
  • Article 5: Correlation between the polarity and the growth process
  • Recipe 4: Application of the road map
  • Polarity dependence of properties and device performance
  • Optical properties and defect formation
  • Schottky barrier
  • Ohmic contact
  • Surface state
  • Summary and Remarks
  • Acknowledgments

    • Linked Pages

    Cite this article as: MRS Internet J. Nitride Semicond. Res. 9, 1(2004).

    last updated Tuesday, October 18, 2005 9:56:54 AM.

    © 2004-2005 The Materials Research Society MRS Internet Journal of Nitride Semiconductor Research