THE ROLE OF DIFFUSION CURRENT IN THE ELECTROLUMINESCENCE OF GaAs DIODES

The intensity of the principal emission band of zincdiffused GaAs p-n junctions with about 2 x 10 to the 17th power cu cm in the n-type region is proportional to exp(qV/kT). The energy of the peak of this band is independent of the forward bias V for these diodes. If the principal emission band results from the recombination of electrons that diffuse across the junction, and if nonradiative recombination is by far the more probable, then the intensity of the principal emission band is proportional to tau exp(qV/kT), where tau is the minority carrier lifetime in the p-type region. This dependence on tau comes, in part, from the gradient of acceptor concentration in the p-type region. Irradiation with 2-MeV electrons decreases the intensity and increases the forward current at a given voltage. The decrease in intensity is consistent with the above model if 1/tau increases linearly with integrated flux. The increase in current is greater for larger bias, suggesting that only the diffusion component of current is affected by irradiation. (Author)