Large (45meV) electron subband separation in quantum wire arrays formed by self-ordering on v-grooved substrates

Abstract

Realization of uniform, dense arrays of semiconductor quantum wires (QWRs) with subband separation >kBT is important for the investigation and application of one-dimensional structures. We have demonstrated uniform arrays of GaAs/AlGaAs QWRs grown by organometallic chemical vapor deposition on V-grooved substrates showing record-large subband separation. The crescent-shaped wires are formed in situ at the comer of two intersecting {111} A planes due to diffusion of the Ga and Al species1. The smaller diffusion length of Al results in rapid recovery of the radius of curvature at the bottom of the GaAs crescents during growth of subsequent AlGaAs barriers. This recovery is characterized quantitatively using transmission electron microscopy (TEM) data. With sufficiently thick barriers, quantum well layers grown on the nonplanar substrate self-order to form vertical arrays of QWRs having identical size and shape. Modeling of the QWR subbads based on TEM cross sections of the structure yields subband separations of 45, 11 and 30meV for electrons, heavy holes and light holes, with effective wire width of 9.5nm for electrons. Photoluminescence excitation spectra show enhanced absorption at the QWR subbands at temperatures as high as 200K (kBT=17.2meV) with observed electron-heavy hole subband separation of ~50meV, in good agreement with the model.