Optical characterization of two-dimensional charge density in GaAs-(Al0.3Ga0.7As) multiple quantum wells

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Abstract
Utilizing the photoluminescence emission and excitation techniques, we can determine the concentration of two‐dimensional (2D) plasma in GaAs‐(Al0.3 Ga0.7As) multiple quantum wells (MQW) at lattice temperature ∼5 K; the results are consistent with the Hall densities. The optical processes investigated also provide the information on the uniformity of 2D electron gas concentration between the wells, which is not available by Hall measurements. The resonant Raman scattering method was taken as an auxiliary tool to confirm the intersubband transition in MQW and substantiates a two‐band model. The absorption edge of the photoluminescence excitation spectrum, especially the low‐energy tail, was fitted with a Fermi distribution function. The results indicate that the temperature of the 2D plasma, Tc, was around 20 K during the measurements.