Abstract

One may strongly modify the linear and nonlinear optical properties of semiconductor materials by quantum confinement of carriers to wires or dots. We describe a new method for achieving this confinement, based on inhomogeneous strain, that applies to a wide variety of semiconductors. We deposit a compressively stressed overlayer onto a semiconductor substrate that contains, for example, an epitaxial layer, or a quantum well. The stressed overlayer is then patterned and etched into arrays of wires and dots. The inhomogeneous strain pattern thus produced in the substrate lowers the bandgap under the center of the wire or dot, creating both lateral and vertical electron, and exciton, confinement. For example, we have patterned strain in a GaAs epitaxial layer by etching a compressed diamondlike carbon overlayer into dots and wires of 100-400 nm in width. Potential wells for excitons in those structures, shown in photoluminescence red shifts, are >50 MeV, with electron zeropoint energies of up to 4 MeV for the smaller structures. We compare our photoluminescence, excitation spectroscopy, and photoluminescence decay time measurements for a variety of strain-confining structures with band structure theory based on finite-element calculations of the strain patterns.

© 1989 Optical Society of America