Molecular beam epitaxial growth of InGaAsInGaAsP quantum wires on V-grooved InP substrates with (1 1 1) sidewalls

Bulk InGaAsP and InGaAsInGaAsP quantum well structures have been grown by gas source molecular beam epitaxy on V-grooved InP substrates having (1 1 1)A and (1 1 1)B sidewalls. The growth of the InGaAsP layer in a (1 1 1)A V-groove results in a flat and wide bottom, which rules out the possibility of the formation of InGaAsInGaAsP quantum wires (QWRs). However, the growth of the InGaAsP layer in (1 1 1)B V-grooves results in a sharper bottom so that crescent-shaped InGaAsInGaAsP quantum wells are formed such that QWR behaviour is possible. Transmission electron microscopy shows that the crescent-shaped InGaAs layer has a very large thickness variation at the V-groove bottom and that all layers at the V-groove bottom are free of extended defects. The photoluminescence from different spatial regions of the sample has been identified using a selective etching technique. Two peaks are associated with the QWRs at V-groove bottom, with the higher energy one apparently being from the second lateral subband transition. The energy separation between these two peaks is consistent with values calculated from the measured thickness variation. Consistent with QWR behaviour, the photoluminescence is polarized, with a stronger signal along the wire direction than perpendicular to the wire direction.