Cathodoluminescence study of orientation patterned GaAs films for non linear optics
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0891-EE03-20.1
Cathodoluminescence study of orientation patterned GaAs films for non linear optics M.Avella1, J. Jiménez1, D.Bliss2, C. Lynch2, D Weyburne2 1 Física de la Materia Condensada, ETSII, 47011 Valladolid, Spain 2 Air Force Research Laboratory, Hanscom AFB, MA 01731, USA
ABSTRACT Zincblende semiconductor materials such as GaAs and ZnSe are very promising for the generation of tunable IR signals by quasi phase-matched nonlinear optical frequency conversion. Orientation patterned GaAs crystals (OP-GaAs) were grown by low-pressure hydride vapor phase epitaxy (HVPE) on lithographically prepared templates. Cathodoluminescence (CL) imaging was used to study these epitaxial films, which consist of periodic domains of inverted crystallographic orientation. The challenge is to achieve thick vertical domains and to minimize sources of optical loss. Both the domain walls and crystal defects may contribute to transmission losses, therefore, a characterization of both is necessary to improve the OP-GaAs crystal performance. The stress and non radiative recombination activity of the domain walls were investigated. The presence of dislocation glide was revealed and CL spectral imaging was used to observe the stress distribution around both the domain walls and the dislocations. INTRODUCTION Tunable sources in the mid-IR spectral range are potentially useful for applications such as remote sensing, medical imaging, spectroscopy, and military IR countermeasures. Non linear optical frequency conversion is an attractive approach for the generation of tunable infrared signals (1-3). GaAs is a good candidate material for use in frequency conversion due to its large second order non linear optic coefficient (d14=96 mp/V), its transparency in the spectral range of interest (1µm-15 µm), its high damage threshold and its excellent mechanical and thermal properties. It also offers the possibility of integration with semiconductor lasers. Unfortunately, GaAs does not have intrinsic properties, which allow for phase matching of the waves involved in the nonlinear frequency conversion process. GaAs is an optically isotropic material without birefringent phase matching and electric poling induced birefringence is not possible because GaAs is not a ferroelectric material. By use of an appropriate modulation of the second order susceptibility in the wave propagation direction, it is possible to obtain quasi phase matching (QPM). One method for producing quasi phase matched GaAs involves the use of arrays of periodically inverted crystallographic domains. Such periodic antiphase domains (APDs) have been demonstrated to be suitable for frequency conversion (4). When fabricated by epitaxial growth on templates patterned with stripes of alternating crystallographic orientation, these types of structures are called orientation patterned GaAs (OP-GaAs) (4). Propagation losses are one of the concerns for the use of OP-GaAs crystals as frequency converters. The challenge is to maintain the domain structure patterned on the template through ove
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