The Application of Photon-Driven Cryoetching to - and Nanostructure Fabrication

The application of a photon-driven, dry, low-temperature etching technique to the fabrication of features in GaAs and related materials is described. A unique feature of this etching is that it does not rely on the bombardment of the sample by accelerated ions, which has been shown to induce damage to the underlying material. The chemistry of the etching, as well as the etching apparatus, are described. The dependence of the etch rate on the various system parameters is measured, and a phenomenological model of the etching based on multilayer physisorption is proposed. The use of this etching for different materials, including GaAs, Al_{rm x}Ga _{rm 1-x}As, InAs, and GaSb, and the ability to achieve deep-submicrometer lateral resolution with this etch technique are shown. Photoluminescence spectroscopy and Schottkey-barrier formation on the etched surface show that the etching induces minimal or no damage to the sample substrate. This technique is applied to the etching of small features from quantum-well material, an application that is especially sensitive to sidewall damage. The luminescence of these features shows that this etching technique induces minimal damage to the sample sidewall. To study the effects of ion etching on the luminescence of these features, we use magnetron-enhanced reactive ion etching to etch identical structures. Samples etched with a 30 V bias exhibit a damage-induced decrease in luminescence efficiency as the etch depth is increased, while sample etched with a 75 V bias show no detectable damage. Lateral confinement of the charge carriers to the center of the feature by electrostatic bandbending is observed in the spectra of the smallest features etched by magnetron-enhanced reactive ion etching at 75 V. Finally, the use of cryoetching in conjunction with various novel patterning techniques is shown.