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

Abstract

Photoluminescence (PL) of high‐quality GaAs/AlGaAs–based heterostructures (HS) shows a remarkable time‐dependent response to microwave irradiation pulses at temperature 2 K. The mw‐frequency was 36 GHz and the modulation pulse widths varied in a wide range. Sharp PL intensity flashes (reaching 100 fold enhancement) at the leading or/and trailing mw‐pulse edges are observed. The transient PL response exhibits a complex interplay of various mw‐induced physical processes: electron heating, electron and exciton density changes as well as an interaction of electrons, holes and excitons with non‐equilibrium acoustic phonons that are emitted by the mw‐heated 2DEG. It is noted that in commonly studied cw, mw‐induced PL (or resistivity) modulation, the observed (cw) effects are determined by a combination of these processes. We developed a model that considers the instantaneous mw‐induced electron heating and following relaxation of the photoexcited electrons, excitons and acoustic phonon flux. Using this model we simulate various types of mw‐induced PL transients observed in undoped HS's as well as in HS's that contain a 2DEG. These simulations prove that non‐equilibrium acoustic phonons play an important role in the mw‐induced PL dynamics. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Imaging of magnetoplasmons excited in a two-dimensional electron gas

“…7,17 Under mw irradiation, the 1S and 2S FE PL intensities strongly increase (solid curves) as compared to those at P mw =0 (curves with circle symbols). 7,18 For the MDQW sample, 2De-h PL spectra are shown for two 2DEG density values (Fig.1c). Under mw irradiation, the spectra broaden, and the PL intensity increases at high photon energies (gray-colored area), as compared to the spectra observed at P mw = 0.…”

“…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.…”

Mechanism of microwave-induced photoluminescence modulation and optically detected resonances due to a two-dimensional electron gas in a heterostructure

“…The relaxation times of ␦n, ␦n x are slower ͑ϳ10 −4 -10 −7 s͒. 19,22,24 The bolometric effect relaxation ͑⌬T L ͒ is very long. 14 Therefore, studying transient dynamics is important in clarifying the physical mechanisms that govern the effects caused by electron heating in semiconductor heterostructures.…”