Direct growth of (AlGa)As/GaAs quantum wires by metalorganic vapour phase epitaxy

Abstract

Trapezoidal or triangular (AlGa)As/(GaAs quantum wire structures are realized by direct growth using metalorganic vapour phase epitaxy (MOVPE). The principle of the new approach as well as detailed growth investigations are presented and discussed. The concept takes advantage of the different growth rates on (100) and {111} planes as a function of substrate temperature to transfer a trapezoidal GaAs stripe structure (stripe width in the μm-range), defined by simple photolithography and selective wet chemical etching, into a (AlGa)As/GaAs trapezoidal or triangular quantum wire structure in the nm-range. A growth rate enhancement on the (100) top stripe plane for submicrometer widths is observed for both GaAs as well as (AlGa)As, this behaviour being of key importance for a precise design of geometrical wire widths. Using high-resolution scanning electrom microscopy (SEM) investigations, the realization of (AlGa)As/GaAs quantum wire structures with lateral structures sizes of about 30 nm is proven. Optical investigations by using photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy reveal the intrinsic character of the quantum wire luminescence. A distinct difference in the polarization dependence of these 1d structures as compared to quantum well systems is found. A blue shift of up to 170 meV with respect to the GaAs band gap is observed for triangular quantum wires with a reduction in nominal geometrical width to 5 nm.