OPTICAL STUDY OF SEGREGATION EFFECTS ON THE ELECTRONIC-PROPERTIES OF MOLECULAR-BEAM-EPITAXY GROWN (IN,GA)AS GAAS QUANTUM-WELLS/

Indium segregation in InxGa1-xAs/GaAs (0.3<x less than or equal to 0.5 ) quantum wells grown by molecular-beam epitaxy and its influence on t heir electronic properties are investigated using thermally detected o ptical absorption. A kinetic model is used to derive concentration pro files and applied to interpret experimental data. The dependence of th e In surface segregation on growth temperature and growth rate is stud ied. It is shown that a decrease of the substrate temperature is the b est method to limit the segregation process kinetically. From a fit of the kinetic model to experimental data, the conduction-band offset ra tio Q(c) is found to be independent of indium composition x between 0. 2 and 0.5 (Q(c)=0.64+/-0.01). The exciton wave function is calculated using a variational technique involving a transfer-matrix formalism to study the influence of potential shape on excitonic properties. Only a slight increase in oscillator strength with In segregation is observ ed for the fundamental excitonic transition.