Microwave-modulated photoluminescence of a two-dimensional electron gas

Abstract

The low-temperature photoluminescence ͑PL͒ of GaAs/ AlGaAs quantum wells and heterojunctions containing a high mobility two-dimensional electron gas ͑2DEG͒ is studied under microwave ͑mw͒ irradiation of 36 GHz. The analysis of the mw-modulated PL ͑MPL͒ spectra allows us to elucidate the effects of mw radiation on the 2DEG. For low magnetic field strengths ͑B Ͻ 0.5 T͒, we show that the MPL spectral shape is due to energy redistribution of the photoexcited holes, as affected by the mw-heated 2DEG. For the mechanism that causes the nonequilibrium hole-energy redistribution, we propose that it is the interaction of the holes with low-energy acoustic phonons emitted by the mw-heated 2DEG. This underlying physical mechanism gives rise to the optically detected 2DEG cyclotron resonance at low B. For B Ͼ 0.5 T, optically detected resonances are observed at B values that depend on the 2DEG density, and they occur near integer electron filling factors. We argue that these resonances result from a slight 2DEG density increase under mw irradiation with a concurrent, low-energy PL spectral shift due to small band-gap narrowing.

Imaging of magnetoplasmons excited in a two-dimensional electron gas

“…1b,c are due to mw-heating of the 2D-electrons. [7][8][9][18][19][20] Fig . 2 shows the PL spectral variations along the excitation strip (y-direction) as imaged through the spectrometer.…”

Dynamics of microwave‐induced processes in photoexcited GaAs/AlGaAs heterostructures

“…Recently, we proposed that the MPL spectrum of the 2DEG-hole PL results from the hole energy redistribution caused by non-equilibrium acoustic phonons that are emitted by the hot 2DEG [7]. We invoke this process in order to explain the observed decrease in PL peak intensity (at 1.5215 eV, Fig.…”

Magneto-photoluminescence of charged excitons from MgxZn1−xO/ZnO heterojunctions

“…Although the reason is not clear at the moment, stronger localization effect in ZnO/Mg 0.2 Zn 0.8 O SHJ may be responsible for this difference. It should be noted that three kinds of the 2DEG-related recombination have been reported so far: (1) recombination between the two-dimensional electrons and the localized hole near the interface [11,23], (2) two-dimensional electron-hole recombination between the 2DEG and a photoexcited hole (2De-h) [21], and (3) recombination of the charged excitons [24].…”

“…The bulk crystal is a commercial single crystal from Tokyo-Denpa Company Ltd., grown by hydrothermal method, followed by chemo-mechanical polish (Mitsubishi Chemicals) [18,19]. PL [21,22]. A weaker PL peak observed for the bulk is assigned to the donor-bound exciton (D 0 5 X) [20].…”