Nitrogen-Activated Bowing Of Dilute Inyga1-Yas1-Xnx Based On Photoreflectance Studies

The dependence of the fundamental band gap and higher-lying critical-point energies of dilute-nitrogen Ga1-yInyAs1-xNx epilayers on nitrogen mole fraction (x), for xless than or equal to0.0125, and temperature, from 20 to 300 K, was investigated by photoreflectance spectroscopy. The band gap, E-G, was found to decrease with increasing x in a highly nonlinear manner. The bowing parameter (the second-order parameter b in a quadratic expression for the dependence of E-G on x) was found to become less negative with increasing x; the value of b changed from -50 eV, at very low nitrogen fraction, to -20 eV, at x>0.01. These results strongly suggest that nitrogen-related impurity levels arise within the band gap of dilute-nitrogen Ga1-yInyAs1-xNx alloys. (C) 2003 American Institute of Physics.