MICROSCALE CHARACTERIZATION OF EPITAXIAL SEMICONDUCTING HOMOLAYERS .1. CATHODOLUMINESCENCE

A model of the cathodoluminescence (CL) intensity originated from Gallium Arsenide epitaxial layers is developed. The dependence of the CL intensity on the electron beam voltage is investigated in the particular case of a structure which resembles field effect transistors: . an n type uppermost layer grown on a acceptor doped ([N(A)] congruent-to 10(15) CM-3) layer, the substrate being semiinsulating. The influence of the parameters on which the CL intensity depends is detailed. The surface and interface recombination velocities and the minority carrier diffusion length can be determined in regions of the order of one micron3. As an illustration of the proposed method of characterisation, experiments were performed at room temperature, in a scanning electron microscope, on GaAs homojunctions grown by molecular epitaxy with an uppermost layer silicon doping level of 4 x 10(17) and 2 x 10(18) CM-3. The minority carrier diffusion length is found to decrease from about 1 mum to 0.5 mum when increasing the doping level. The surface and interfaces recombination velocities are estimated to be as high as 10(6) cm/s.