Journal of Crystal Growth, Vol.477, 114-117, 2017
CdTe layer structures for X-ray and gamma-ray detection directly grown on the Medipix readout-chip by MBE
This work investigates the potential of CdTe semiconducting layers used for radiation detection directly deposited on the Medipix readout-chip by MBE. Due to the high Z-number of CdTe and the low electronhole pair creation energy a thin layer suffices for satisfying photon absorption. The deposition takes place in a modified MBE system enabling growth rates up to 10 mu m/h while the UHV conditions allow the required high purity for detector applications. CdTe sensor layers deposited on silicon substrates show resistivities up to 5.8 x 10(8) Omega cm and a preferred (111) orientation. However, the resistivity increases with higher growth temperature and the orientation gets more random. Additionally, the deposition of a back contact layer sequence in one process simplifies the complex production of an efficient contact on CdTe with aligned work functions. UPS measurements verify a decrease of the work function of 0.62 eV induced by Te doping of the CdTe. (C) 2017 Elsevier B.V. All rights reserved.
Keywords:molecular beam epitaxy;semiconducting cadmium compounds;radiation detection;polycrystalline deposition