Internal Transitions of Neutral and Charged Magneto-Excitons in GaAs/AlGaAs Quantum Wells

Abstract

We have used Optically Detected Resonance (ODR) spectroscopy to probe the electronic properties of undoped and barrier-doped GaAs/Al 0.3 Ga 0.7 As multiple-quantum-well (MQW) samples with well widths between 12.5 and 20 nm in magnetic fields up to 15 T at low temperatures. The simultaneous observation of electron and hole CR along with several internal transitions of neutral excitons (IETs) verifies the symmetry-related energy differences of the internal transitions to differences between electron and hole CR. The observed degeneracy of the 1s 3 2p + IET from the two radiative magneto-excitons is due to the very small electron g-factor. ODR measurements on 20 nm wide MQWs (not-intentionally-and barrier-doped) exhibit transitions of the negatively charged excitonic complex.

Charged excitons in a dilute two-dimensional electron gas in a high magnetic field

“…The magneto-optical properties of quasi-twodimensional (2D) electron systems have been intensively investigated experimentally [1][2][3][4][5][6][7][8][9][10][11][12][13] and theoretically.…”

Charged Magnetoexcitons in Two Dimensions: Isolated X? and Many-Electron Effects

“…The bulk of the experimental work to date has been concentrated on interband magneto-optics. More recently, intraband internal transitions of charged excitons have been studied [14]. Theoretically, the behavior of X À at high B (charged magnetoexcitons), has been studied in the strictly-2D geometry [15], in realistic QWs [16,17], in a confining potential of a donor ion [18] and a quantum dot [19], and in a spherical geometry [20,21] 2 Þ.…”

Dynamical equilibrium between excitons and trions in CdTe quantum wells in high magnetic fields

“…For the measurements in the magnetic field we used a setup which allowed us to perform PL and ODR measurements simultaneously. 35,36 The sample was placed in the Faraday geometry in a cryostat at a temperature Tϭ1.4 K inside a Bitter magnet, which can produce dc fields up to 17 T. To perform polarized measurements a /4 plate and a polarizer were mounted directly above the sample in the cryostat before the luminescence entered the fiber. The FIR radiation was produced by a methanol-gas-based FIR laser system, which was pumped by a 40-W cw CO 2 laser.…”

“…Furthermore, apart from the CR we do not see other resonant features such as intra-exciton or intra-trion transitions, which are reported for GaAs based structures. 33,36,44,45 The broad ⌬PL signal is attributed to non-resonant heating, because of the following reasons: ͑i͒ The signal is similar for all FIR laser lines used ͑Fig. 5͒ and has the same sign as the CR, which is unambiguously due to heating of the electron system.…”