A. E. Willner

The Laser‐Controlled Micrometer‐Scale Photoelectrochemical Etching of III–V Semiconductors

Laser-controlled photoelectrochemical etching of III-V semiconductors using micrometer-sized illumination regions has been investigated for varying laser parameters (power, spot size, wavelength) and etching solutions. The etching has been applied to a wide variety of semiconductor doping types. The micrometer spot size of the laser can induce higher etch rates for a given intensity when compared to broad illumination. In addition, the process has micrometer-scale resolution and highly directional etch anisotropy. In this electroless process the laser etching rate is influenced by light-induced voltage shifts in the surface potential. Finally, the dependence of the process resolution on carrier diffusion and etch depth is discussed

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.

Interaction of deep-ultraviolet laser light with GaAs surfaces in aqueous solutions

We have investigated the surface oxidation of GaAs and subsequent oxide dissolution that is caused by ultraviolet laser light at 257 nm in an aqueous environment. This process has a chemistry distinct from the related process that uses visible light. Further, unique light-guided surface-relief structures result from the ultraviolet chemistry and the ultraviolet optical properties of the semiconductor surface.

Graded-effective-index waveguiding structures fabricated with laser processing

The technique of laser direct-writing was used to fabricate low-loss, rib-like waveguides on GaAs/A1GaAs material. Since this is a inaskless fabrication process, laser-etched structures such as bends, tapers, and Y-branches are readily demonstrated. The ability to smoothly control the etch depth, and thus the effective index of refraction across the wafer, was used to make a compact directional coupler. Finally, the reduction of losses in waveguide tapers and bends by grading the effective index will be discussed.

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.

Modeling of riblike waveguides with isolation trenches of finite width

A method for calculating the propagation and loss characteristics of riblike waveguiding structures having isolation trenches of finite width is presented.

Surface Potential Characterization Of The Photoelectrochemical Etching System By Photoreflectance And Electroreflectance Techniques

We use the modulation techniques of electrolyte electroreflectance and photoreflectance to locally probe the semiconductor surface potential of various semiconductor/electrolyte interfaces. Changes in the surface potential are important in determining the rate of charge transfer in both electrode and electrodeless photochemical etching.