D. V. Podlesnik

Laser fabricated GaAs waveguiding structures

We have applied the technique of laser‐induced etching to fabricate rib waveguides on a GaAs/AlGaAs heterostructure system. Light confinement of these guides was controlled by varying the depth of the etched trenches. Additionally, we have demonstrated directional couplers and two‐level waveguides using the in situ depth control of this single‐step process.

GaAs surface oxidation and deoxidation using electron cyclotron resonance oxygen and hydrogen plasmas

We have used x‐ray photoelectron spectroscopy to investigate electron cyclotron resonance oxygen plasma oxidation and hydrogen plasma deoxidation of GaAs surfaces. Experimental evidence shows that ECR oxidation at room temperature forms a stoichiometric oxide layer that is primarily composed of As2O5 and Ga2O3. A hydrogen plasma is shown to clean GaAs surfaces and recover surface order, even at room temperature. Sample heating (200–300u2009°C) expedites the removal of Ga2O3 and improves surface order. In addition, no significant differences in oxidation and deoxidation were observed for sample biasing, either positively or negatively.

Ultraviolet‐light‐enhanced reaction of oxygen with gallium arsenide surfaces

Light‐enhanced reaction of oxygen with gallium arsenide surfaces by irradiation with deep‐UV, near‐UV, and visible light was studied using Auger electron spectroscopy and x‐ray photoelectron spectroscopy for submonolayer and above monolayer regimes, respectively. The onset of a strong wavelength dependence of the enhanced oxidation was observed after the oxygen coverage reached more than one‐half a monolayer. An abrupt threshold for this wavelength dependence was also observed at ∼4.1‐eV photon energy. A possible mechanism is presented to explain this strong wavelength dependence.

Effect of carrier confinement on the laser-induced etching of GaAs/AlGaAs heterostructures

Laser‐induced photochemical etching was used to etch GaAs/AlGaAs multilayered material. In this carrier‐driven process, the confinement of photogenerated holes to the alternating GaAs layers resulted in the controlled lateral etching of buried GaAs layers. An application of this etching technique to forming microcleaved laser facets is described.

Study of Thermal Oxide Solid-State Reaction on GaAs Surfaces

In this paper, we will present a study of the thermal reaction of AsjOs with GaAs at temperatures below 550°C using monochromatic X-ray photoelectron spectroscopy (MXPS). A solid-state interface reaction of 4GaAs + 3AS 2 O 5 → 2Ga 2 O 3 + 3AS 2 O 3 + 4As, which includes the usual native oxide thermal reaction: 2GaAs + AS 2 O 3 → Ga 2 O 3 + 4As, as well as a decomposition reaction AS 2 O 5 → AS 2 O 3 + O 2 is responsible for the thermal reaction in this temperature range.

The effect of a thin ultraviolet grown oxide on metal–GaAs contacts

Photochemistry has been used to grow very thin oxide layers (3–10 A) on GaAs(100) surfaces. Some of these oxides have been annealed to produce Ga‐rich oxide surface layers. Electrical characterization of metal contacts deposited on these surfaces show a much greater variation of Schottky barrier heights for the oxidized surfaces, especially for the Ga‐rich oxide surfaces. The observed variation is ∼25% of the GaAs band gap for Ga‐rich oxide surfaces, compared to ∼8% for clean surfaces. The change in barrier heights is toward the ideal Schottky limit for contacts without interface states. This behavior suggests that the oxidized surface has reduced the density of interface states present in the metal–GaAs contacts.