Direct magneto-optical observation of a quantum confined one-dimensional electron gas

Abstract

The energy spectra of isolated one-dimensional (1D) electron channels have been studied by photoluminescence (PL) in zero and finite magnetic fields B. Arrays of periodic quantum wires (period = 290–400 nm, width = 150–170 nm) were etched fr modulation-doped Al xGa 1−xAs/GaAs heterojunctions, with special low concentration Be δ-doping in the buffer layer to increas the PL intensity. PL recombination with holes bound to acceptors of this δ-layer offers the possibility to measure directly the density of states of a degenerate electron system below the Fermi edge. We were able to attain the 1D quantum limit, i.e., occupation of only the lowest 1D subband at B = 0 and to measure, at small B, a characteristic quadratic B-dispersion of the 1D subband edge and thereby to determine the 1D confinement energy, ħohms 0. We find typical values of h ̷ ohms 0 = 3–5 meV which a compatible with the rather narrow channel width of 30–40 nm.