Effect of Yb concentration on the resistivity and lifetime of CdTe:Ge:Yb codoped crystals

The resistivity and electron lifetime of CdTe:Ge:Yb crystals are reported, demonstrating that the effect of Yb concentration is crucial for accurate electrical compensation. It is also demonstrated that the codoping of CdTe with Ge as deep donor and with Yb as rare-earth element could be a promising way to obtain semiinsulating CdTe crystals with good transport properties. High resistivity 5 10 9 cm and lifetime 9 s were obtained, thus confirming the beneficial effect of rare-earth dopingThis work has been partly supported by the projects CAM SENSORCDT S-0505/MAT/0209, CAM FOTOFLEX S-0505/ENE-123, and EU FP6 PHOLOGIC 017158. E.S. also acknowledges the Spanish MEC for the fellowship FPU 2003-1388.Peer reviewe

EBL Bi-layer resist scheme for CdTe/Si submicron structures for lift-off processing

The fabrication of CdTe multi-pixel imaging detectors with the pixels of submicron size and photonic structures requires the use of high resolution lithography technique such as electron beam lithography (EBL). The main drawback of CdTe submicron structures made by the combination of EBL and conventional lift-off processes is the large roughness at the edges of CdTe structure, due of the use of a single polymethylmethacrylate (PMMA). To solve this problem, we used a bi-layer resist scheme of two polymers with different lithography characteristics. The bottom layer was a copolymer which has both minor molecular weight and higher sensibility than the upper PMMA layer. Different exposure doses were experimented, and the length and shape of the undercutting of copolymer layer under PMMA were characterized in the optimum range from 250 to 500 μC/cm2. These results were applied to the fabrication of submicron CdTe structures by EBL, and subsequent CdTe vapor phase epitaxy (VPE) and lift-off step processing. © 2007 Elsevier B.V. All rights reserved.Peer Reviewe

Vapour growth of Cd(Zn)Te columnar nanopixels into porous alumina

4 páginas, 4 figuras.-- PACS: 81.05.Dz; 81.07.Bc; 81.15.Kk; 68.55.Jk.-- New Developments in Radiation Detectors - Proceedings of the 10th European Symposium on Semiconductor Detectors, 10th European Symposium on Semiconductor Detectors.The vapour phase growth (VPG) of CdTe and Cd1−xZnxTe was performed in order to investigate the formation of Cd(Zn)Te columnar nanostructures, which could serve as a basis for micropixels usable for further development of X- and gamma-ray high-resolution imaging devices. The possibility to form the “Cd(Zn)Te-in-porous alumina” nanostructures by VPG has been demonstrated. The Cd(Zn)Te crystals integrated into nanoporous alumina have shown to have photoluminescence properties compatible with those of the bulk crystals and planar epitaxial layers. Further investigations are going on to improve the structural quality of Cd(Zn)Te nanocrystals.This work has been partly supported by the European Commission (FP6 program, PHOLOGIC project, Contract No. 017158) and the Spanish Ministry of Science and Technology via the program ‘Ramon y Cajal’ and project MAT2003-09873-C02.Peer reviewe