First-principles simulations have been performed for [001]-ordered Mn/Ge and Mn/GaAs " digital alloys " , focusing on the effects of i) a larger band-gap and ii) a different semiconducting host on the electronic structure of the magnetic semiconductors of interest. Our results for the exchange constants in Mn/Ge, evaluated using a frozen-magnon scheme, show that a larger band-gap tends to give ...

A far-infrared p-type germanium laser with active crystal prepared from ultra pure single-crystal Ge by neutron transmutation doping ~NTD! is demonstrated. Calculations show that the high uniformity of Ga acceptor distribution achieved by NTD significantly improves average gain. The stronger ionized impurity scattering due to high compensation in NTD Ge is shown to have insignificant negative i...

We have computed the contribution of UV-light-induced densification to the refractive-index modulation of fiber Bragg gratings. Our results confirm that, for strong gratings written in Ge-doped silica fibers with 248-nm UV light, density changes account for a major part of the photosensitivity effect.

Relativistic band theoretical calculations reveal that intrinsic spin Hall conductivity in hole-doped archetypical semiconductors Ge, GaAs, and AlAs is large [approximately 100(planck/e)(Omega cm)(-1)], showing the possibility of a spin Hall effect beyond the four-band Luttinger Hamiltonian. The calculated orbital-angular-momentum (orbital) Hall conductivity is one order of magnitude smaller, i...

This work presents the fabrication of thermopiles with high output voltage. A series of mixed thick/thin-film thermopiles were performed – one of the arms of the thermocouples was screen-printed (PdAgor Ag-based thick-film layers), the second was made of magnetron sputtered semiconductor (compositions based on Ge). The output parameters (thermoelectric force ET [V], internal resistance Ri [Ω], ...

We discuss the analytical expressions that describe the displacement field resulting from the inscription of a Bragg grating in a Ge-doped optical fiber. The equations stem from a phenomenological approach and allow calculation of the induced stresses. Our model provides an efficient tool to analyze the effects of radiation-induced density variations on the properties of fiber Bragg gratings.

Semiconductors that exhibit room-temperature ferromagnetism are central to the development of semiconductor spintronics. Transition metal (TM)-doped ABC2 are a promising class of such system. These ternary compound semiconductors have two metal sites A and B that can be substituted by the TMs. A site preference for TM incorporation is crucial for a possible explanation of ferromagnetism since d...

Permanent photobleaching of blue luminescence with a maximum at ~390 nm in Ge-doped fiber preforms by exposure to the third harmonic (354 nm) of a Nd:YAG laser has been observed. The experimental results show that photodestruction of a germanium oxygen-deficient center can occur without photoionization.

Stark broadening of Zeeman absorption lines caused by inhomogeneous electric fields in highly compensated Ge has been studied by means of far-infrared magneto-optical absorption spectroscopy measurements. A number of transmutation-doped Ge single crystals with a systematically varying compensation ratio were employed. The broadening of the full width at half maximum ~FWHM! of an absorption line...

The anisotropic thermoelectric transport properties of bulk silicon strained in the [111]-direction were studied by detailed first-principles calculations focusing on a possible enhancement of the power factor. Electron and hole doping were examined in a broad doping and temperature range. At low temperature and low doping an enhancement of the power factor was obtained for compressive and tens...