Epitaxial Ge-crystal arrays for X-ray detection

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Authors

KREILIGER Thomas FALUB Claudiu Valentin ISA Fabio ISELLA G. CHRASTINA D. BERGAMASCHINI R. MARZEGALLI A. KAUFMANN R. NIEDERMANN P. NEELS A. MÜLLER E. MEDUŇA Mojmír DOMMANN Alex MIGLIO Leo VON KANEL Hans

Year of publication 2014
Type Article in Periodical
Magazine / Source Journal of Instrumentation
MU Faculty or unit

Central European Institute of Technology

Citation
Web http://iopscience.iop.org/1748-0221/9/03/C03019
Doi http://dx.doi.org/10.1088/1748-0221/9/03/C03019
Field Solid matter physics and magnetism
Keywords Materials for solid-state detectors; Solid state detectors; X-ray detectors
Description Monolithic integration of an X-ray absorber layer on a Si CMOS chip might be a potentially attractive way to improve detector performance at acceptable costs. In practice this requires, however, the epitaxial growth of highly mismatched layers on a Si-substrate, both in terms of lattice parameters and thermal expansion coefficients. The generation of extended crystal defects, wafer bowing and layer cracking have so far made it impossible to put the simple concept into practice. Here we present a way in which the difficulties of fabricating very thick, defect-free epitaxial layers may be overcome. It consists of an array of densely packed, three-dimensional Ge-crystals on a patterned Si(001) substrate. The finite gap between neighboring micron-sized crystals prevents layer cracking and substrate bowing, while extended defects are driven to the crystal sidewalls. We show that the Ge-crystals are indeed defect-free, despite the lattice misfit of 4.2%. The electrical characteristics of individual Ge/Si heterojunction diodes are obtained from in-situ measurements inside a scanning electron microscope. The fabrication of monolithically integrated detectors is shown to be compatible with Si-CMOS processing.
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