On the Bandstructure in GaInN/GaN Heterostructures - Strain, Band Gap and Piezoelectric Effect


Christian Wetzel, Shugo Nitta, Tetsuya Takeuchi, Shigeo Yamaguchi, H. Amano, I. Akasaki
Department of Electrical and Electronic Engineering, Meijo University

This article was received on Friday, August 28, 1998 and accepted on Tuesday, October 6, 1998.

Abstract

A study of the optoelectronic properties of strained 40 nm Ga1-xInxN layers on GaN films is presented. The fact of pseudomorphic strain leads to a new interpretation of the film composition when derived from x-ray scattering. In addition we directly confirm that strain induces huge piezoelectric fields in this uniaxial system by the observation of Franz-Keldysh oscillations in photoreflection. As a function of composition (0 < x < 0.2) and strain we derive the electronic band gap energy and the piezoelectric field strength. We interpret both in terms of effective bowing parameters and piezoelectric coefficients, respectively. From a spatially resolved micro photoluminescence at room temperature we find no evidence for spatial band gap or composition variations of more than 60 meV over the length scale from 1 to 50 µm (x=0.187) in our material. At the same time, an observed discrepancy between photoluminescence peak energy and photoreflection band gap energy increases with x to some 160 meV. We attribute this redshift to photon assisted tunneling in the huge piezoelectric fields (Franz-Keldysh effect).

Outline

  • Introduction
  • Experimental
  • Strain and Composition
  • Spatial Fluctuations
  • Electronic Band Gap Energy (0<x<0.2)
  • Piezoelectric Fields
  • Piezoelectric Constants
  • Luminescence Band Gap
  • Conclusions
  • Acknowledgments

    • Linked Pages

    Cite this article as: MRS Internet J. Nitride Semicond. Res. 3, 31(1998).

    last updated Wednesday, April 5, 2000 5:18:50 PM.

    © 1998-2000 The Materials Research Society MRS Internet Journal of Nitride Semiconductor Research
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