Anomalous Temperature dependence of Fermi-edge Singularity in Modulation-doped AlGaAs/InGaAs/GaAs hetero-structures

Abstract

AbstractThe temperature and power dependence of Fermi-edge singularity (FES) in high-density two-dimensional electron gas, specific to pseudomorphic AlxGa1-xAs/InyGa1-yAs/GaAs heterostructures is studied by photoluminescence (PL). In all these structures, there are two prominent transitions E11and E21considered to be the result of electron-hole recombination from first and second electron sub-bands with that of first heavy-hole sub-band. FES is observed approximately 5 -10 meV below the E21transition. At 4.2 K, FES appears as a lower energy shoulder to the E21transition. The PL intensity of all the three transitions E11, FES and E21grows linearly with excitation power. However, we observe anomalous behavior of FES with temperature. While PL intensity of E11and E21decrease with increasing temperature, FES transition becomes stronger initially and then quenches-off slowly (till 40K). Though it appears as a distinct peak at about 20 K, its maximum is around 7 - 13 K.