Thin-film GaSb diodes were fabricated and investigated for room-temperature radiation detection. GaSb PN junction-based detectors were fabricated by use of both ion-implantation and epitaxial methods, and were compared for crystal quality and detector performance. The implanted junctions were obtained by p-type Be ion-implantation in n-type GaSb substrates whereas the epitaxial junctions were grown by solid-source molecular beam epitaxy. Alpha-particle and fission-fragment peaks were observed in spectra from 241 Am and 252 Cf. A highly uniform response was obtained from epitaxially grown GaSb junctions whereas large pulse-height response variation was observed for the implanted diodes. The devices were fabricated in the form of metalized squares with dimensions varying from 2 9 2 mm 2 to 500 9 500 lm 2 . Reducing the size reduced detection efficiency but also increased the pulse height response and thus the signal-to-noise ratio, consistent with diode capacitance and output voltage pulse relationships. Cross-sectional transmission electron microscope imaging revealed very high-quality material for the epitaxial structure and implantation-induced damage for the implanted material.
The behavior of electron and hole transport in semiconductor materials is influenced by lattice-mismatch at the interface. It is well known that carrier scattering in a confined region is dramatically reduced. In this work, we studied the effects of coupling both the strain and confinement simultaneously. We report on the fabrication and characterization of nanoscale planar, wall-like, and wire-like Si/SiO2 structures. As the Si nanostructure dimensions were scaled down to the quantum regime by thermal oxidation of the Si, changes to the band structure and carrier effective mass were observed by both optical and electrical techniques. Transient-time response measurements were performed to examine the carrier generation and recombination behavior as a function of scaling. Signal rise times decreased for both carrier types by an order of magnitude as Si dimensions were reduced from 200 to 10 nm, meaning that the carrier velocity is increasing with smaller scale structures. This result is indicative of decreased Si bandgap energy and carrier effective mass. Photoluminescence measurements taken at 50K showed changes in the PL response peak energies, which illustrates changes in the band structure, as the Si/SiO2 dimensions are scaled.
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