PHOTOREFLECTANCE STUDIES OF (AL, GA)AS GAAS HETEROSTRUCTURES AND DEVICES/

Experimental and theoretical PR spectra are reported for (AlGa)As/GaAs single heterostructures, (AlGa)As/GaAs quantum well structures as wel l as MESFET and HEMT structures. The theoretical spectra are calculate d by means of a novel technique which combines the two methods previou sly used for spatially inhomogeneous systems: the transfer matrix meth od for light propagation between different layers, and perturbation th eory for light propagation within each weakly inhomogeneous layer. The electric field distribution is calculated from an integral equation w hich holds under quite general conditions including incomplete dopant ionizations and carrier degeneracies. In most of the spectra, pronounc ed interference effects show up. Due to them, PR spectra from quantum wells are sensitive to the well distance from the surface. Besides int erference effects, field inhomogeneities like broadening of Franz-Keld ysh oscillations manifest themselves in the reported spectra. A contro versy in the literature concerning PR spectra from (AlGa)As/GaAs singl e heterostructures is solved by means of the novel calculation techniq ue.