FERMI-EDGE SINGULARITIES IN THE OPTICAL-EMISSION OF DOPED DIRECT AND INDIRECT QUANTUM-WELLS

The luminescence spectrum of doped direct and indirect quantum wells i s studied. The Bethe-Salpeter equation is solved in a three band model of parabolic wells. By shifting the electron and the hole confining p arabolic potentials with respect to each other, we found a strong enha ncement at the Fermi edge. We take an infinite mass for the hole and w e find an increasing signal of the spectrum at the Fermi edge when two conditions are fulfilled: (i) the separation between the electrons an d hole gravity centers is of the order of the well width and (ii) the Fermi edge is close to the bottom of the second conduction subband. Th e effects of temperature are analyzed.