GROWTH OF MODULATION-DOPED GAAS ALGAAS QUANTUM WIRES ON V-GROOVE PATTERNED SUBSTRATES/

In order to achieve modulation-doped V-groove quantum wires for transp ort measurements, two different combinations of precursor groups have been tested: TMGa, TMAl and AsH3 (set 1) and TEGa, dimethylethylaminea lane (DMEAAI) and AsH3 (set 2). Perfect selectivity of growth on SiO2 masked substrates was obtained for set 1 and quantum wires were formed with lateral dimensions of 20 nm. However, selective epitaxy results in large local growth rate variations in areas of different SiO2 surfa ce coverage, complicating the design of modulation-doped structures. U sing precursor set 2, growth is not selective. Crystalline regions on unmasked areas join smoothly the polycrystalline film growing with a s imilar growth rate on SiO2 masked regions. The result is a growth rate independent of the local substrate patterns. Since the semi-insulatin g polycrystalline film does not degrade the quality of crystalline reg ions, these samples exhibit the first magnetotransport measurements th at clearly indicate the existence of a 2DEG in our V- and U-groove str uctures. As a result we are able to define a layer structure that comb ines the specific advantages of precursor set 1 and 2 for future work.