Free-to-bound and interband recombination in the photoluminescence of a dense two-dimensional electron gas

Low-temperature photoluminescence (PL) measurements of a pseudomorphic modulation-doped $\mathrm{GaAs}/{\mathrm{In}}_{0.2}{\mathrm{Ga}}_{0.8}\mathrm{As}/{\mathrm{Al}}_{0.2}{\mathrm{Ga}}_{0.8}\mathrm{As}$ quantum well containing a dense two-dimensional electron gas ${(n}_s=1.6\mathrm{}\times {10}^{12}{\mathrm{cm}}^{-2})$ in a magnetic field are reported. Two well-defined high-energy cutoffs of the PL spectra are observed. Results of the magnetospectroscopic study indicate that these cutoffs are due to the recombination of free electrons from the vicinity of the Fermi level with localized and free holes, respectively. The localization energy of the bound hole is determined. It is shown that the free-to-bound recombination is much more effective that the interband recombination in the investigated structure.