THEORY OF THE EFFECT OF MAGNETIC-FIELD ON THE EXCITONIC PHOTOLUMINESCENCE LINEWIDTH IN SEMICONDUCTOR ALLOYS

We report a calculation on the effect of the magnetic field on the excitonic photoluminescence linewidth in intentionally undoped semiconductor alloys. We assume that the dominant mechanism for the line broadening is due to the potential fluctuations caused by the disorder of the components of the alloy. Variations in the local concentrations from the global value are accounted for by using statistical mechanical arguments developed by Lifshitz [Adv. Physics 13, 483 (1965)] and then related to the linewidth. When a magnetic field is applied to the system, the effective volume of the optical probe, namely, the excition, is reduced causing it to become more responsive to the statistical potential fluctuations. This results in the broadening of the photoluminescence line as a function of the magnetic field. Variation of the excitonic linewidth as a function of the magnetic field and alloy composition in Al(x)Ga1-xAs is presented.