Photoluminescence of Double Quantum Wells: Asymmetry and Excitation Laser Wavelength Effects

Abstract

Circularly polarized photoluminescence (PL) spectroscopy measured at 19 K on GaAs/AlGaAs symmetric and asymmetric double quantum wells (DQW) is reported. The PL is obtained by exciting the sample with a circularly polarized (left or right) laser in order to create an initial unbalanced distribution of electron spins in the conduction band and, in this way, obtain the electron spin lifetime . The effects of the excitation laser wavelength are estimated by exciting with laser wavelengths of 701.0, 787.0, 801.5, and 806.5 nm. The increase of with the excitation wavelength is attributed to the lower initial quasimomentum k of the excited carriers, which also reduces spin–orbit relaxation processes. is found to be higher in asymmetric DQWs: this is attributed to the wider QWs in these samples, which reduces spin relaxation due to the Dresselhaus mechanism. In addition, a smaller contribution from the Rashba mechanism is also detected by comparing samples with built‐in electric fields of different orientations defined by doped barrier layers.