Relationship between photoluminescence spectra and low-field electrical properties of modulation-doped AlGaAs/GaAs quantum wells

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Abstract
We describe the influence of sheet charge density and crystalline quality on the photoluminescence (PL) spectra of AlGaAs/GaAs n-type modulation doped quantum wells (MDQWs). We discuss the various contributions to the PL linewidth at 4.2 K. The linewidth at 77 K is approximately equal to the Fermi energy, and is independent of crystalline quality, making it a good measure of sheet carrier density. At 4.2 K, the crystalline quality also influences the PL linewidths; however, the carrier density can be deduced from the high-energy cutoff point of the PL spectra. The ratio of 77 K to 4.2 K linewidths correlates fairly well with the crystalline quality, as measured by the 77 K Hall mobility. Our calculations of the band diagram, wavefunctions, and carrier densities provide a deeper understanding of these structures. Results of this work have applications in nondestructive testing of large area wafers for uniformity in sheet carrier density and mobility as well as in the design of novel optoelectronic devices.