Nuclear Instruments and Methods in Physics Research A 491 (2002) 444–451 The X-ray response of InP: Part B, synchrotron radiation measurements Alan Owens a, *, A. Peacock a , M. Bavdaz a , G. Brammertz a , F. Dubeck " y b , V. Gostilo c , D. Gryaznov c , N. Haack d , M. Krumrey e , A. Loupilov c a Science Payloads Technology Division, ESA/ESTEC, Postbus 299, 2200AG Noordwijk, The Netherlands b Institute of Electrical Engineering, Slovak Academy of Sciences, D ! ubravsk ! a cesta 9, 842 39 Bratislava, Slovakia c Baltic Scientific Instruments, Ganibu dambis 26, P.O. Box 33, LV-1005 Riga, Latvia d HASYLAB at DESY, Notkestrasse 85, D 22607 Hamburg, Germany e Physikalisch-Technische Bundesanstalt, Abbestrasse 2-12, D-10587 Berlin, Germany Received 28 April 2002; accepted 30 May 2002 Abstract In this, the second part of a detailed study into the X-ray response of InP, we present results of a series of X-ray measurements on a 3.142mm 2  180 mm thick semi-insulating InP detector at the BESSY II and HASYLAB synchrotron radiation research facilities. Photon metrology was carried out at energies ranging from 8 to 100keV. Additional measurements were made using radioactive and fluorescent target sources. At 601C, under full-area illumination, the FWHM energy resolution was 2.4keV at 5.9keV rising to 8.5keV at 59.54keV. Under pencil-beam illumination,themeasuredresolutionsweregenerallyless,being2keVFWHMat8keVrisingapproximatelylinearlyto 5keV at 100keV. Analysis of the energy resolution function indicates that poor charge transport presently limit the performanceofInPdetectorsandspecificallyholetrapping.Thisisborneoutbytheobservedlow-energytailingofthe pulseheightspectraatintermediateandhighenergies.Atverylowcountrates,itwasfoundthatthedevicewaslinearto within 1%. However, for count rates above B100s 1 and energies above B50keV,thedetectorbegantodisplaytime variable gain shifts indicative of polarization effects. Thespatialuniformityofthedetectorwasinvestigatedbyrasterscanninga50  50 mm 2 ,15keVmonoenergeticX-ray beam across the active area. Apart from a few localized areas, the detector response was found to be reasonably uniform at the 10% level, although inconsistent with that expected from counting statistics alone (2%). r 2002 Elsevier Science B.V. All rights reserved. PACS: 07.85n; 29.40Wk; 61.80e Keywords: Compound semi-conductors; InP; X-rays; Spectroscopy 1. Introduction Indium phosphide (InP) is a group III–V direct band-gap material whose structural and electronic propertiesaresimilartoSiandGaAs.Ithasoneof *Corresponding author. Tel.: +37-71-565-5326; fax: +31- 71-565-4690. E-mail address: aowens@rssd.esa.int (A. Owens). 0168-9002/02/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. PII:S0168-9002(02)01179-8