Spatially Resolved Characterization of Plastic Deformation Induced by Focused-Ion Beam Processing in Structured InGaN/Ga
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1020-GG01-07
Spatially Resolved Characterization of Plastic Deformation Induced by Focused-Ion Beam Processing in Structured InGaN/GaN Layers R. Barabash1,2, G. Ice1, R. Kroger3, H. Lohmeyer3, K. Sebald3, J. Gutowski3, T. Bottcher3, D. Hommel3, W. Liu4, and J.-S. Chung1,5 1 Materials Science and Technology, Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge, TN, 37831-6118 2 University Of Tennessee, Knoxville, TN, 37996 3 Institute of Solid State Physics, Bremen, Germany 4 Advanced Photon Source, Argonne, IL, 60439 5 Soongsil University, Seoul, Korea, Republic of ABSTRACT Polychromatic X-ray microbeam analysis (PXM) results of structural changes caused by FIB machining in nitride heterostructures are discussed in connection with microphotoluminescence (µ-PL), fluorescent analysis, scanning electron (SEM) and transmission electron microscopy (TEM) data. It is shown that FIB processing distorts the lattice in the InGaN/GaN layer not only in the immediate vicinity of the processed area but also in surrounding volumes. A narrow amorphized top layer is formed in the direct ion beam impact area. INTRODUCTION Focused-ion beam (FIB) machining is a promising technique for the realization of novel micro- and nanostructured optoelectronic devices- especially for the important nitride materials system [1], which is difficult to process by conventional etching techniques. For example, there is intense recent research directed at the application of FIB machining to create vertical semiconductor microcavities that possess three-dimensionally confined optical modes for surface-emitting lasers. Because these and other potential optoelectronic devices are sensitive to defect distributions, there is a strong need to assess the damage induced on GaN and related materials by FIB machining. Although widely used for TEM-sample preparation and for processing of edge-emitters, FIB is increasingly applied to prepare mesa-structures for single-dot spectroscopy and for the preparation of micropillars out of planar vertical-cavity surface-emitting lasers (VCSEL) samples. In such materials induced damage can be important. Of course the damage induced by FIB machining has been previously studied in Si [2] and other materials [3]. For the nitrides however, there are only a few reports with respect to possible ion damage induced by FIB machining and similarly few reports on the induced damage impact on mesoscale structure and optical properties [4]. Below we present the results of polychromatic X-ray microbeam analysis of the damage in InGaN layers structured with FIB. The results are complemented by fluorescence, SEM, TEM and micro-photoluminescence (µ-PL) analyses.
EXPERIMENTAL DETAILS A FEI Nova 200 NanoLab FIB system was used to prepare reference structure samples consisting of InGaN/GaN multi quantum wells grown by metal-organic vapor phase epitaxy on GaN on sapphire templates (Fig. 1). Some samples were capped with 100nm SiO2 layer before FIB processing. Both capped and uncapped samples were studied. Each structure consists o
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