Lasing mechanisms in high-quality T-shaped quantum-wire lasers

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T-shaped quantum wire laser structures containing 20 wires of 14nmx6nm size each with atomically flat interfaces have been fabricated by cleaved edge overgrowth with growth interrupt annealing in MBE. We studied these laser structures by PL scanning measurements with our home made motor scanning system, excitation power dependent PL measurements, lasing measurements with optical excitations, gain measurements by Shaklee method and Hakki-Paoli method. We made similar measurements for a single wire laser structures containing only one quantum wire with the same cross-sectional size. We also performed detailed PL scanning measurements for an n-type modulation-doped single quantum wire structure with a gate to tune one-dimensional electron gas density like a FET.Thanks to the PL scanning measurements we were able to select high-quality quantum wire regions with PL width of 1-1.5meV from regions with larger PL width or with localized states. From PLE measurement results, reliable assignments to one-dimensional free excitons and continuum states have been done on the basis of comparison with rigorous theoretical calculations including the Coulomb interactions. Line shape of continuum state was measured for the first time.Finally, excitation power dependent PL measurements have demonstrated formation of biexcitons and electron-hole plasmas in the wires. Comparison with the lasing data have shown that the origins of gain in lasing are not free excitons that were claimed before, but are strongly-Coulomb correlated electron-hole plasmas.