LATERAL CONFINEMENT BY LOW-PRESSURE CHEMICAL-VAPOR DEPOSITION-BASED SELECTIVE EPITAXIAL-GROWTH OF SI1-XGEXSI NANOSTRUCTURES

Among the growth approaches being considered currently to realize quan tum dots and quantum wires is the selective epitaxial growth on patter ned substrates. With this technique the feature size and geometry are mainly limited by the lithographic process. With optical lithography w e achieved a lateral dimension of greater than or equal to 0.4 mu m. T herefore, to further reduce the lateral dimension, but still using opt ical lithography, the;tendency toward facet formation during selective epitaxial growth was investigated. Si0.70Ce0.30 multiple quantum well structures with Si0.935Ge0.065 spacers and buffers were deposited on (001) Si. The buffer thickness was varied so as to achieve facet junct ion. While on large areas the Si0.935Ge0.065 buffer was relaxed, for d ots less than or equal to 300 mu m or narrower the structures remained strained even for buffer thicknesses exceeding by a factor of two-thr ee the critical thickness of large area. In dots and wires where facet junctioning has taken place a rounded region between facets (approxim ately 50 nm broad) in the quantum well layers was observed. In wires o riented parallel to [100] sidewalls self-organized wire formation and vertical correlation of these growth induced wires was observed. The p hotoluminescence of all dots and wires down to the lowest achieved dim ension and including the self-organized wires is strong, with the inte gral intensity normalized to the surface coverage for 100 nm dots exce eding by a factor of 50 the emission from unpatterned areas. (C) 1997 American Institute of Physics.