FERMI-EDGE SINGULARITY OBSERVED IN A MODULATION-DOPED ALGAN GAN HETEROSTRUCTURE/

In this letter, we report on the observation of Fermi-edge singularity in a modulation-doped AlGaN/GaN heterostructure grown on a c-face sap phire substrate by NH3 source molecular beam epitaxy. The two-dimensio nal electron gas (2DEG) characteristic of the structure is manifested by variable temperature Hall effect measurements down to 7 K. Low-temp erature photoluminescence (PL) spectra show a broad emission band orig inating from the recombination of the 2DEG and localized holes. The en hancement in PL intensity in the high-energy side approaching Fermi le vel was observed at temperatures below 20 K. At higher temperatures, t he enhancement disappears because of the thermal broadening of the Fer mi edge. (C) 1998 American Institute of Physics. [S0003-6951(98)02543- 1].