Speaker
Tamiraa Ganbold
Description
This work deals with investigation of novel position sensitive devices
based on InGaAs/InAlAs Quantum Well (QW) for several applications of either
synchrotron or conventional light sources. Such QW devices may be used as fast and efficient detectors due to the
direct, low-energy band gap and high electron mobility at Room Temperature
(RT).
Metamorphic In0.75Ga0.25As/
In0.75Al0.25As QWs containing a two-dimensional electron
gas (2DEG) were grown by Molecular Beam Epitaxy (MBE). The carrier mobility at
RT was 1.2×104 cm2 V-1 s-1.
Two devices with size of 5×5-mm2
were prepared by using optical lithography. In the first, the active layers
were segmented into four electrically insulated quadrants. Indium Ohmic
contacts were realized on the corner of each quadrant (for readout) and on the
back surface (for bias).
In the second, the QW was left unsegmented
and covered by 400 nm of Al providing a single bias electrode, while four
readout electrodes were fabricated on the back side by depositing and
segmenting a Ni/Ge/Au layer. This configuration should be beneficial for the
fabrication of pixelated detectors.
Photo-generated carriers can be collected
at the readout electrodes by biasing form either the QW side or the back side
of the devices during beam exposure. Individual currents obtained from each
electrode allow to monitor both the position and the
intensity of the impinging beam for photon energies ranging from visible to
hard X-ray.
Such detector prototypes were tested with
Synchrotron Radiation (SR), conventional X-rays and 400-nm laser light. The
results obtained with X-ray SR show how these devices exhibit high charge
collection efficiencies, which can be imputed to the charge-multiplication
effect of the 2DEG inside the QW. Moreover, the position of the beam can be
estimated with a precision of 800 nm in the segmented QW. A lower precision of
10 µm was recorded in the unsegmented QW due to the charge diffusion through
the 500-µm-thick wafer. When tested with a 400-nm, 100-fs table-top laser,
these devices responded with 100-ps rise-times to such ultra-fast laser pulses.
Author
Tamiraa Ganbold
Co-authors
Dr
Diane Eichert
(Elettra – Sincrotrone Trieste S.C.p.A., Trieste, Italy)
Dr
Giorgio Biasiol
(IOM CNR, Laboratorio TASC, Area Science Park, Trieste, Italy)
Dr
Giuseppe Cautero
(Elettra – Sincrotrone Trieste S.C.p.A.,Trieste, Italy)
Dr
Matias Antonelli
(Elettra – Sincrotrone Trieste S.C.p.A.,Trieste, Italy)
Dr
Ralf Menk
(Elettra – Sincrotrone Trieste S.C.p.A., Trieste, Italy)
Dr
Riccardo Cucini
(Elettra – Sincrotrone Trieste S.C.p.A., Trieste, Italy)
Dr
Werner Jark
(Elettra – Sincrotrone Trieste S.C.p.A., Trieste, Italy)
