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Proceedings Paper

First demonstration and performance of AlGaN based focal plane array for deep-UV imaging
Author(s): J.-L. Reverchon; S. Bansropun; J. A. Robo; J. P. Truffer; E. Costard; E. Frayssinet; J. Brault; F. Semond; J. Y. Duboz; M. Idir
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Paper Abstract

We present several prototypes to extend the range of AlGaN focal plane arrays from near UV to deep UV range (200 nm - 4 nm). Arrays include 320x256 pixels with a pitch of 30 μm and are based on Schottky photodiodes. AlGaN is grown on a silicon substrate. After a flip-chip hybridization, silicon substrate is thinned and removed by dry etching. The tricky point is to maintain the membrane integrity. By using a honeycomb structure in the Si substrate, after hybridization, we were able to keep the membrane plane and rigid, avoid the crack expansion, and thus maintain the membrane integrity. The structure includes an Al.35Ga.65N active layer grown on a thick Al.55Ga .45N window layer, with a graded AlGaN layer in between. The high quality materials are grown by MBE. The Al.55Ga.45N window layer is also thinned by dry etching down to the gradual layer and desertion layer where a higher internal electric field takes place. The results show that the dry etching process doesn't affect the readout circuit properties. The dark current is negligible and non uniformity in etching slightly contributes into a constant offset. The measured noise factor, a bit more than 100 electrons rms, is due to reset noise in the integration capacitance and in other parasitic capacitances. With a peak response at 300 nm of 35%, the responsivity is 1% at 266 nm and in the deep UV range. The spectral responsivity measured on a synchrotron line at a wavelength of 2nm reaches more than 200% due to multiple photoexcitation.

Paper Details

Date Published: 23 September 2009
PDF: 10 pages
Proc. SPIE 7474, Sensors, Systems, and Next-Generation Satellites XIII, 74741G (23 September 2009); doi: 10.1117/12.830287
Show Author Affiliations
J.-L. Reverchon, Thales Research & Technology (France)
S. Bansropun, Thales Research & Technology (France)
J. A. Robo, Thales Research & Technology (France)
J. P. Truffer, Thales Research & Technology (France)
E. Costard, Thales Research & Technology (France)
E. Frayssinet, Ctr. de Recherche sur l'Hétéro-Epitaxie et ses Appliations, CNRS (France)
J. Brault, Ctr. de Recherche sur l'Hétéro-Epitaxie et ses Appliations, CNRS (France)
F. Semond, Ctr. de Recherche sur l'Hétéro-Epitaxie et ses Appliations, CNRS (France)
J. Y. Duboz, Ctr. de Recherche sur l'Hétéro-Epitaxie et ses Appliations, CNRS (France)
M. Idir, Synchrotron SOLEIL (France)

Published in SPIE Proceedings Vol. 7474:
Sensors, Systems, and Next-Generation Satellites XIII
Roland Meynart; Steven P. Neeck; Haruhisa Shimoda, Editor(s)

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