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We have fabricated Ge/Si heterojunction photodetectors with high responsivities of 550 mA/W at 1.32 mu m and 250 mA/W at 1.55 mu m and time responses shorter than 850 ps. High quality Ge was epitaxially grown on Si using ultrahigh vacuum/chemical vapor deposition followed by cyclic thermal annealing. The beneficial effect of the post-growth thermal annealing on the electrical properties of Ge epilayers, due to the reduction of threading-dislocation densities, is confirmed by the dramatic enhancement of the performance of the photodetectors. (C) 2000 American Institute of Physics. [S0003-6951(00)03410-0]

Deep level transient spectroscopy has been employed in a study of impurity-interstitial defect reactions in silicon following room-temperature electron irradiation. Three defects have been isolated and identified from their reactions and electrical properties as Cs-Ci, Ci-Oi, and Ps-Ci. The Cs-Ci, ME[(0.10), (0.17)] and Ps-Ci, ME[(0.21), (0.23), (0.27), (0.30)] defects exhibit metastable structural transformations. Our results reveal the multistructural nature and chemical reactivity of the silicon self-interstitial.

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We present data on oxygen diffusivity in silicon for the temperature range 270–400 °C. The diffusivity is determined from the recovery kinetics of a stress induced dichroism in the 9-μm oxygen infrared absorption band. We combine our data for well dispersed oxygen (i.e., crystals heat treated at 1350 °C for 20 h), with Mikkelsen’s recent mass transport work at higher temperature to obtain the diffusivity, D=0.17 exp (−2.54/kT), for the range 330–1240 °C. We have also found that the oxygen atomic hopping times can be as much as 100 times faster in crystals that have not received the 1350 °C heat treatment.