High-density electron gas induced by atomic ordering in undoped Ga0.5In0.5P/GaAs heterostructure

We investigated two-dimensional properties of electrons accumulated at a long-range ordered Ga_0.5In_0.5P/GaAs heterointerface by magneto-photoluminescence (PL) measurements. The disordered Ga_0.5In_0.5P/GaAs sample shows a typical GaAs-PL spectrum for the bulk GaAs grown by metalorganic vapor-phase epitaxy. On the other hand, the GaAs-PL spectrum for the ordered sample with order parameter η of 0.30 shows transitions related to a quantized electron state in a triangular potential buried at the heterointerface and emission of the Fermi-edge singularity. The observed PL spectrum for the ordered sample demonstrates that a two-dimensional electron gas is induced at the Ga_0.5In_0.5P/GaAs heterointerface. In magneto-PL measurements, anisotropy of the reduced mass between parallel and perpendicular to the heterointerface was confirmed. Furthermore, the clear optical Shubnikov-de Haas oscillation was found in PL transition energy under the perpendicular magnetic field. The sheet-carrier density of 2DEG is deduced from the period of the observed Shubnikov-de Haas oscillation to be ∼1.20×10¹² cm^-2.