Composition and Carrier Concentration Dependence of the Electronic Structure of InyGa1-yAs1-xNx Films With Nitrogen Mole Fraction Less Than 0.012

Published

November 1, 2005

Author(s)

Youn S. Kang, Lawrence H. Robins, Anthony Birdwell, Alexander J. Shapiro, W. R. Thurber, Mark D. Vaudin, M M. Fahmi, D Bryson, S N. Mohammad

Abstract

The electronic structure of Si-doped InyGa1-yAs1-xNx films on GaAs substrates, grown bynitrogen-plasma-assisted molecular-beam epitaxy, was examined by photoreflectance PR spectroscopy at temperatures between 20 and 300 K. The films were approximately 0.5 m thickand had nitrogen mole fraction between x=0.0014 and x=0.012, measured indirectly by asecondary-ion-mass spectrometry calibration; indium mole fraction between y=0.052 and y=0.075, measured by electron-dispersive x-ray spectroscopy; and carrier concentration between 2 1016 and 1.1 1018 cm-3, measured by Hall effect. Three critical-point transitions were identifiedby PR: the fundamental band gap highest valence band to the lowest conduction band ; thespin-orbit split valence band to the lowest conduction band; and the highest valence band to anitrogen impurity band above the lowest conduction band . The measured critical-point energieswere described by a band anticrossing BAC model with the addition of a Burstein-Mossband-filling term. The fitted BAC parameters were similar to previously reported values. The Nimpurity level was located 0.3004 0.0101 eV above the conduction-band edge at 20 K and0.3286 0.0089 eV above the conduction-band edge at 295 K. The BAC interaction parameter was2.588 0.071 eV. From the small magnitude of the Burstein-Moss energy shift with increasingcarrier concentration, it was inferred that the carrier concentration probed by PR is reduced from thebulk Hall-effect carrier concentration by a reduction factor of 0.266 0.145. The PR linesbroadened with increasing carrier concentration; the line broadening tracked the predictedBurstein-Moss energy shift for the bulk carrier concentration. The surface-normal lattice constantsof the films were measured by x-ray diffraction. Comparison of the measured lattice constants withVegard s law showed the presence of tensile strain in the surface-normal direction with magnitudebetween 1.5 10-3 and 3.0 10-3. The effect of strain on the PR energies was too small toobserve.

Citation

Journal of Applied Physics

Volume

98

Pub Type

Journals

Keywords

band anti-crossing model, band structure, Burstein-Moss effect, compound semiconductors, Hall effect, photoreflectance, x-ray diffraction

Citation

Kang, Y. , Robins, L. , Birdwell, A. , Shapiro, A. , Thurber, W. , Vaudin, M. , Fahmi, M. , Bryson, D. and Mohammad, S. (2005), Composition and Carrier Concentration Dependence of the Electronic Structure of InyGa1-yAs1-xNx Films With Nitrogen Mole Fraction Less Than 0.012, Journal of Applied Physics (Accessed April 18, 2024)