Anomalous Temperature dependence of Fermi-edge singularity in modulation-doped AlGaAs/InGaAs/GaAs hetero-structures

摘要

The temperature and power dependence of Fermi-edge singularity (FES) in high-density two-dimensional electron gas, specific to pseudomorphic AlxGai-xAs/InyGa^. yAs/GaAs heterostructures is studied by photoluminescence (PL). In all these structures, there are two prominent transitions Ei i and E21 considered 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 E21 transition. At 4.2 K, FES appears as a lower energy shoulder to the E21 transition. The PL intensity of all the three transitions E| 1, FES and E21 grows linearly with excitation power. However, we observe anomalous behavior of FES with temperature. While PL intensity of E| 1 and E21 decrease 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.