We investigate the effects of light-induced wet etching ͑LIWE͒ on sidewall profile and etch rate for n-and p-type GaAs bulk, epitaxial AlGaAs layers and two different types of laser heterostructure using three different etch masks and three light-emitting diodes as light sources. The experiments show that the LIWE parameters ͑light-source wavelength, mask conductivity, sample layer structure͒ control the sidewall angle and etch rate. The technique successfully produced vertical sidewalls and "on-demand" etch-stop layers in laser heterostructure using sulfuric acid ͑H 2 SO 4 ͒: hydrogen peroxide ͑H 2 O 2 ͒: DI water ͑H 2 O͒ etch system. Wet etching has potential advantages over dry etching, 1-3 including lower cost, smoother surfaces, and larger etch rates. Integrated devices require a variety of etched-sidewall profiles and angles ranging from shallow etched-slopes for electrical contacts to vertical flat smooth surfaces for integrated laser mirrors. Vertical etches must maintain good control of lateral etching to inhibit smoothing of patterned features, prevent undercutting of metal contacts, and to increase the degree of integration for some types of devices including micro-optical-electrical-machines ͑MOEMs͒ with close-fitting moveable parts. 4 The sidewall profiles obtained from wet chemical etching normally depend on the etching solution and the material crystal direction. 5-8 Light-induced wet etching ͑LIWE͒ 9 potentially expands the fabrication options offered by anisotropic dry etching by using light to break the normal crystal-plane etching and thereby provides control over the sidewall profiles with angles ranging from several degrees to 90 degrees while retaining many favorable wetetching properties.The present research investigates the effects of LIWE on sidewall profiles and etch rate for n-and p-type GaAs bulk, epitaxial AlGaAs layers, and two different types of laser heterostructure with three different etch masks. The sidewall angle and etch rate are controlled by the etch condition including wavelength of the light source, electrical property of the mask, and layer structure of the material. The results show that a judicious choice of wavelength during the LIWE of heterostructure can transform a normally etching layer into an etch-stop layer or alter the etched-sidewall angle. The LIWE experiments reported here have successfully etched a vertical sidewall in laser heterostructure material.Photochemical etching has many possible applications such as maskless etching, selective etching, and control of the etched side wall profile. Podlesnik et al. 10 show that laser light increases the etch rate in illuminated regions of the sample. Deep trenches in n-type GaAs and AlGaAs have been fabricated by applying a focused laser beam 10-12 directly to a bulk sample positioned within the etching solution. Van de Ven et al. 13 fabricate square contours on GaAs samples by scanning a laser beam in a square pattern. The technique gives rise to the possibility of maskless etching whereby accurate control of the ...

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We present the effects of the photo-assisted (532 nm) semiconductor dissolution on sidewall profile and etch rate for two different types of GaAs/AlGaAs laser heterostructure and two different etch masks. The experiments show that the photo-assisted dissolution characteristics (dissolution rate and side angle profile) strongly depend on the sample layer structure and mask conductivity. The experiments apply optical interference and photoluminescence techniques to determine the surface and photo-carrier dynamics. The research evaluates the application of photo-assisted semiconductor etching to the fabrication of III-V devices using 532 nm coherent illumination. The technique successfully produces vertical sidewalls and on-demand etch-stop layers in laser heterostructure using Sulfuric acid (H2SO4): Hydrogen peroxide (H2O2): DI water (H2O) etch system.

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