ELECTRON-HOLE PLASMA IN PULSE PHOTOEXCITED SINGLE QUANTUM WELLS

We report photoluminescence studies of MOCVD grown, GaAs-Al//xGa//1// minus //xAs single quantum wells which were intensely excited with a pulse dye laser at T equals 2K. For a well width of d approximately equals 40 A, the spectra are interpreted as due to the radiative recombination of a hot electron-hole plasma confined to the well. The density of charge carriers and their temperature depend upon the excitation intensity, and vary in the range of 10**1**1-10**1**3 cm** minus **2 and 100-500K for an absorbed photon flux of 10**1**3-10**1**6 photons-cm** minus **2 per pulse, respectively. The observed spectral features are identified as the e1-hh1 and e1-1h1 transitions and two additional bands which are tentatively assigned to transitions involving virtual bound states of either the electron or the hole. The electron-hole plasma spectra of the d approximately equals 40A sample are strongly polarized perpendicular to the well quantization axis. For wider wells (d approximately equals 80 and 150A) smaller photoexcited carrier densities were observed.