Properties of molecular-beam epitaxy-grown GaNAs from optical spectroscopy

Abstract

GaN x As 1−x layers with different nitrogen concentrations x grown on (001)GaAs substrates by molecular-beam epitaxy have been studied by photoluminescence, optical absorption, and Raman spectroscopy. The content of nitrogen in the layers was determined by x-ray diffraction and secondary-ion-mass spectrometry. The samples can be classified in three categories with respect to the concentration of N: with doping nitrogen concentration, with average content of N less than 0.3, and with x close to 1. From optical measurements and from analysis of x-ray diffraction spectra, different phases are observed in the GaNxAs1−x layers: GaAs, GaN, and the solid ternary solution GaNxAs1−x. In Raman spectra both GaAs-like and GaN-like optical phonons are observed. We have estimated the fundamental band-gap energy in the GaNxAs1−x alloy with low nitrogen concentration up to x=0.04 from absorption measurements, and in GaNxAs1−x with high nitrogen concentration x>0.96 from photoluminescence spectra. Fitting of the experimental data for low x values gives a constant bowing parameter as big as b=−18 eV. This value predicts the band-gap energy for the high nitrogen concentration in agreement with experimental data. Consequently, GaNxAs1−x is predicted to be semimetallic in the range 0.12<x<0.75.

Band Anticrossing in III-N-V Alloys

“…A reduction of the band gap of more than 100 meV per atomic percentage nitrogen was observed in GaNAs [4]. Similar gap reductions were also observed in other III-N-V semiconductor alloys [5][6][7][8][9][10][11][12][13][14][15]. The strong dependence of the band gap on the N content offers a possibility to use the N-containing alloys for a variety of long wavelength optoelectronic devices [9] and in hybrid solar cell designs [14,15].…”

“…However, despite years of extensive experimental and theoretical studies [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], there has been no general consensus on the proper description of the observed effects of N incorporation on the electronic structure of III-N-V alloys. Many of the early experiments on III-N-V alloys were analyzed in terms of the phenomenological Quantum Dielectric Theory [16,17].…”

New Developments in Dilute Nitride Semiconductor Research

“…13 The same result was inferred from studies of the GaNAs near the two binary limits, with the decrease in the energy gap being linear for N fractions as high as 3%. 40 A quadratic form with C=11 eV fit the results of an ellipsometry study for x=3.3% fairly well. 41 Other studies of dilute GaNAs indicated bowing parameters as large as 22 eV.…”

Band anticrossing in dilute nitrides

“…[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] In this article, we show that the effect of nitrogen on the electronic band structure of dilute nitrides can be consistently described in terms of an anti-crossing interaction between localized nitrogen states and the extended conduction-band states of the semiconductor matrix. 6,27 The interaction leads to a significant modification of the band structure of the dilute III-N-V alloys.…”