Schottky CdTe X-ray detectors exhibit excellent spectroscopic performance but suffer from instabilities. Hence it is of extreme relevance to investigate their electrical properties. A systematic study of the electric field distribution and the current flowing in such detectors under optical perturbations is presented here. The detector response is explored by varying experimental parameters, such as voltage, temperature, and radiation wavelength. The strongest perturbation is observed under 850 nm irradiation, bulk carrier recombination becoming effective there. Cathode and anode irradiations evidence the crucial role of the contacts, the cathode being Ohmic and the anode blocking. In particular, under irradiation of the cathode, charge injection occurs and peculiar kinks, typical of trap filling, are observed both in the current-voltage characteristic and during transients. The simultaneous access to the electric field and the current highlights the correlation between free and fixed charges, and unveils carrier transport/collection mechanisms otherwise hidden.
Toyama, H.; Higa, A.; Yamazato, M.; Maehama, T.; Ohno, R.; Toguchi, M. Quantitative analysis of polarization phenomena in CdTe radiation detectors. Jpn. J. Appl. Phys. 2006, 45, 8842–8847.
[3]
Cola, A.; Farella, I. The polarization mechanism in CdTe Schottky detectors. Appl. Phys. Lett. 2009, 94, doi:10.1063/1.3099051.
[4]
Principato, F.; Gerardi, G.; Turturici, A.A.; Abbene, L. Time-dependent current-voltage characteristics of Al/p-CdTe/Pt X-ray detectors. J. Appl. Phys. 2012, 112, doi:10.1063/1.4764325.
[5]
Vartsky, D.; Goldberg, M.; Eisen, Y.; Shamai, Y.; Dukhan, R.; Siffert, P.M.; Koebel, J.M.; Regal, R.; Gerber, J. Radiation induced polarization in CdTe detectors. Nucl. Instrum. Method. Phys. Res. A 1988, 263, 457–462.
[6]
Du, Y.; LeBlanc, J.; Possin, G.E.; Yanoff, B.D.; Bogdanovich, S. Temporal response of CZT detectors under intense irradiation. IEEE Trans. Nucl. Sci. 2003, 50, 1031–1035.
[7]
Bale, D.S.; Szeles, C. Nature of polarization in wide-bandgap semiconductor detectors under high-flux irradiation: Application to semi-insulating Cd(1-x)Zn(x)Te. Phys. Rev. B 2008, 77, doi:10.1103/PhysRevB.77.035205.
[8]
Sato, G.; Fukuyama, T.; Watanabe, S.; Ikeda, H.; Ohta, M.; Ishikawa, S.; Shiraki, H.; Ohno, R. Study of polarization phenomena in Schottky CdTe using infrared light illumination. Nucl. Instrum. Method. Phy. Res. A 2011, 652, 149–152.
[9]
Dědi?, V.; Franc, J.; Sellin, P.J.; Grill, R.; Peruma, V. Study on electric field in Au/CdZnTe/In detectors under high fluxes of X-ray and laser irradiation. J. Instrum. 2012, 7, doi:10.1088/1748-0221/7/02/P02011.
[10]
Washington, A.L.; Teague, L.C.; Duff, M.C.; Burger, A.; Groza, M.; Buliga, V. Wavelength dependence on the space charge collection in CdZnTe detectors. J. Appl. Phys. 2012, 111, 113715–113721.
Prokesh, M.; Bale, D.S.; Szeles, C. Fast high-flux Response of CdZnTe X-ray detectors by optical manipulation of deep level occupations. IEEE Trans. Nucl. Sci. 2010, 57, 2397–2399.
[13]
De Antonis, P.; Morton, E.J.; Podd, F.J.W. Infra-red microscopy of Cd(Zn)Te radiation detectors revealing their internal electric field structure under bias. IEEE Trans. Nucl. Sci. 1996, 43, 1487–1490.
[14]
Zumbiehl, A.; Hage-Ali, M.; Fourgeres, P.; Koebel, J.M.; Regal, R.; Siffert, P. Electric field distribution in CdTe and Cd1-xZnxTe nuclear detectors. J. Cryst. Growth 1999, 197, 650–654.
[15]
Khusainov, K.; Antonova, Y.A.; Lysenlko, V.V.; Makhkamov, R.K.; Morozov, V.Z.; Ilves, A.G.; Arlt, R.D. Energy resolution of large-area CdTe p-i-n detectors with charge loss corrections. Nucl. Instrum. Method. Phys. Res. A 2001, 458, 242–247.
[16]
Cola, A.; Farella, I.; Auricchio, N.; Caroli, E. Investigation of the electric field distribution in X-ray detectors by Pockels effect. J. Opt. A Pure Appl. Opt. 2006, 8, S467–S472.
[17]
Sellin, P.J.; Prekas, G.; Franc, J.; Grill, R. Electric field distributions in CdZnTe due to reduced temperature and X-ray irradiation. Appl. Phys. Lett. 2010, 96, doi:10.1063/1.3373526.
[18]
Franc, J.; Dědi?, V.; Sellin, P.J.; Grill, R.; Veeramani, P. Radiation induced control of the electric field in Au/CdTe/In structures. Appl. Phys. Lett. 2011, 98, doi:10.1063/1.3598414.
[19]
Cola, A.; Farella, I.; Mancini, A.M.; Donati, A. Electric field properties of CdTe nuclear detectors. IEEE Trans. Nucl. Sci. 2007, 54, 868–872.
[20]
Uxa, S.; Belas, E.; Grill, R.; Praus, P.; James, R.B. Determination of electric-field profile in CdTe and CdZnTe detectors using transeint-current technique. IEEE Trans. Nucl. Sci. 2012, 59, 2402–2408.
Namba, S. Electro-optical effect of zincblende. J. Opt. Soc. Am. 1961, 51, 76–79.
[23]
Cola, A.; Farella, I.; Anni, M.; Martucci, M.C. Charge transients by variable wavelength optical pulses in CdTe nuclear detectors. IEEE Trans. Nucl. Sci. 2012, 59, 1569–1574.
[24]
Cuzin, M. Some new developments in the field of high atomic number materials. Nucl. Instrum. Method. Phys. Res. A 1987, 253, 407–417.
[25]
De Montmorillon, L.A.; Delaye, P.; Launay, J.C.; Roosen, G. Comparative study of CdTe and GaAs performances from 1 μm to 1.55 μm. Opt. Mater. 1995, 4, 233–236.
[26]
Ramo, S. Currents induced by electron motion. Proc. I.R.E. 1939, 27, 584–585.
[27]
Cola, A.; Farella, I. Electric fields and dominant carrier transport mechanisms in CdTe Schottky detectors. Appl. Phys. Lett. 2013, 102, doi:10.1063/1.4795942.
[28]
Zanichelli, M.; Pavesi, M.; Marchini, L.; Zappettini, A. Studies on charge collection and transport properties on semi-insulating materials in the presence of a non-uniform electric field. Solid State Commun. 2012, 27, 1212–1215.
[29]
Lampert, L.A. Simplified theory of space-charge-limited currents in an insulator with traps. Phys. Rev. 1956, 103, 1648–1656.
[30]
Rose, A. Space-charge-limited currents in solids. Phys. Rev. 1955, 97, 1538–1544.
[31]
Rose, A. Concepts in Photoconductivity and Allied Problems; Interscience: New York, NY, USA, 1963.