Berdermann, E.

Fischer, M.

Gsell, S.

Kis, M.

Mayr, M.

Schmidt, C. J.

Schreck, M.

Stehl, C.

Träger, M.

GSI Repository

Development of Heteroepitaxial DoI Plates for Diamond Detectors∗E. Berdermann1, S. Gsell2, M. Fischer2, M. Kiš† 1, M. Mayr2, C.J. Schmidt2, M. Schreck2, C. Stehl2,and M. Träger11GSI, Darmstadt, Germany; 2University of Augsburg, GermanyTypical size of the chemical vapor deposition (CVD) ho-moepitaxially grown diamond material (also known as thesingle crystal - SC) is limited to some 5 x 5 mm2 due tothe availability of growth substrates made from the high-pressure high-temperature (HPHT) diamond. Presently, theonly material readily available for the production of dia-mond detectors with larger area (∼10 cm2) is polycrys-talline (PC) film grown on silicon wafers with electroniccharacteristics far inferior in comparison to SC material.In order to produce a large-surface high-quality materialfor diamond detectors different techniques for heteroepi-taxial growing of diamond films are being investigated anddeveloped at the University of Augsburg. By using yttrium-stabilized zirconium oxide (YSZ) buffer layer to produceiridium terminated substrate on silicon wafers [1] one cangrow diamond films (also know as the diamond on iridium- DoI) that are far more homogeneous than PC, however,still burdened with defects. In last few years a remarkableimprovement in lowering of the level of impurities and de-fects was achieved so that the presently produced samples -while still not comparable to SC material - are far superiorto any PC material.Most significant structural defect arising in heteroepitax-ial growth are dislocations.In a recent study [2] in which thedensity of threading dislocations was determined by fewmethods over a large sample thickness, an inverse growthdepth behaviour was found. While this at least in principleconfirms that films with very low density of dislocationscan be grown, presently procedure would not be economi-cally effective therefore different growing techniques - e.g.epitaxial lateral overgrowth - are being developed.In order to assess the quality i.e. electronic character-istics of new DoI samples a typical measurement of thecharge collection efficiency (CCE) is performed by us-ing the transient current technique (TCT). Alpha particles(241Am) are used to test the sample with different polariza-tions and drift fields so that the properties for both types ofcharge carriers can be evaluated. In Fig. 1 the set of mea-surements with a recent DoI sample of 190 µm thickness atdifferent drift fields is presented showing the saturation atvalues above 0.8 V/µm. While the overall triangular shapeof wave forms indicate the presence of the charge recombi-nation defects, additional flat-top slope is related to lossesdue to the charge carrier trapping within the sample. Forthis sample we have measured an average CCE of about60% for holes, which is below the level of the best samples∗This work was supported in part by HadronPhysics3 (grant agreementNo 283286 under the EU FP7.)† m.kis@gsi.deFigure 1: Pulse-shapes (waveforms) obtained for the driftof holes across the sample. The CCE is determined bywaveform integration. Each waveform is an average from1000 recorded events.tested (>90%) [3]. On the other hand, the CCE for elec-trons (shown in Fig. 2) of about 40% is much better thanpreviously measured (∼10 %). In this case the saturation isobserved at the higher drift field of 1.2 V/µm.Figure 2: Pulse-shapes for the drift of electrons across thesample with 42 dB pre-amplification.References[1] S. Gsell et al., Appl. Phys. Lett. 84, 4541 (2004)[2] C. Stehl et al., Appl. Phys. Lett. 103, 151905 (2013)[3] E. Berdermann et al., GSI Sci. Rep. 2011, 245FG-S-FRS-07 GSI SCIENTIFIC REPORT 2013342 doi:10.15120/GR-2014-1-FG-S-FRS-07

Development of Heteroepitaxial DoI Plates for Diamond Detectors

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Development of Heteroepitaxial DoI Plates for Diamond Detectors

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