CALCULATION OF EXCHANGE ENERGY IN QUANTUM DOTS - APPLICATION TO POROUS SILICON

We present a variational calculation of the envelope wave function of an exciton inside a cube, in the effective mass approximation, with on e parameter which plays the part of a Bohr radius. This geometry allow s one to reduce the sixfold integrals to threefold integrals which sho rtens tremendously computer calculations. This wave function is used t o obtain the exchange energy and the oscillator strength. The limiting cases (large or small cubes) are recovered. We show that recent exper imental results in porous silicon can be explained without further hyp othesis.