EDGE LUMINESCENCE OF ALN-GAN SOLID-SOLUTIONS

Effects of alloy composition and crystalline structure on the luminesc ence of epitaxial layers of 2H-AlxGa1-xN(0 less than or equal to x les s than or equal to 0.3) solid solutions grown on 6H-SiC substrates wit h GaN sublayers have been investigated. The full width at half-maximum of the x-ray rocking curve for AlGaN has been determined as a functio n of the AIN concentration in the solid solution. From an analysis of the cathodoluminescence spectrum we have determined the position of th e luminescence band near the fundamental absorption edge as a function of the composition of an AlxGa1-xN solid solution at T=300 K: E(x)=3. 39+2.19x+0.65x(2) (eV). The broadening of this band has been studied a s a function of increasing AlN concentration in the solid solution. Th e experimental results have been interpreted using a model of broadeni ng of the edge luminescence band due to a random distribution of alloy components. This mechanism has been shown to produce much stronger br oadening of the edge luminescence band for AlGaN compared with narrowe r-gap III-V solid solutions. Some influence of the GaN sublayer on the structural and luminescence properties of the AlGaN layers has been i dentified. (C) 1996 American Institute of Physics.