Piotr Becla

Application of strong vertical magnetic fields to growth of II–VI pseudo-binary alloys: HgMnTe

Abstract HgMnTe crystals are grown by the vertical Bridgman method in the presence of an applied vertical magnetic field of 30 kG. Reduction of convective intensity in the melt through application of the magnetic field is found to decrease radial macro-segregation and eliminate small-scale compositional undulations in the grown material; the axial compositional profile is found not to be influenced by the magnetic field. These observations are shown to be consistent with a previously proposed model for the residual convection present during growth of this and other similar materials.

Band anticrossing in group II-Ox–VI1−x highly mismatched alloys: Cd1−xMnyOxTe1−x quaternaries synthesized by O ion implantation

Highly mismatched group II-Ox–VI1−x alloys have been synthesized by oxygen implantation into Cd1−yMnyTe crystals. In crystals with y>0.02, incorporation of O causes a large decrease in the band gap. The band gap reduction increases with y; the largest value observed is 190 meV in O-implanted Cd0.38Mn0.62Te. This striking behavior is consistent with the band anticrossing model which predicts that repulsive interaction between localized states of O and the extended states of the conduction band causes the band gap reduction. These large, O-induced effects provide a unique opportunity by which to control the optical and electronic properties in II–VI alloys.

Monolithically integrated, resonant-cavity-enhanced dual-band mid-infrared photodetector on silicon

In this paper, we present experimental demonstration of a resonant-cavity-enhanced mid-infrared photodetector monolithically fabricated on a silicon substrate. Dual-band detection at 1.6 μm and 3.7 μm is achieved within a single detector pixel without cryogenic cooling, by using thermally evaporated nanocrystalline PbTe as the photoconductive absorbers. Excellent agreement between theory and experiment is confirmed. The pixel design can potentially be further extended to realizing multispectral detection.

Resonant-cavity-enhanced mid-infrared photodetector on a silicon platform

In this paper, we demonstrate high optical quantum efficiency (90%) resonant-cavity-enhanced mid-infrared photodetectors fabricated monolithically on a silicon platform. High quality photoconductive polycrystalline PbTe film is thermally evaporated, oxygen-sensitized at room temperature and acts as the infrared absorber. The cavity-enhanced detector operates in the critical coupling regime and shows a peak responsivity of 100 V/W at the resonant wavelength of 3.5 microm, 13.4 times higher compared to blanket PbTe film of the same thickness. Detectivity as high as 0.72 x 10(9) cmHz(1/2)W(-1) has been measured, comparable with commercial polycrystalline mid-infrared photodetectors. As low temperature processing (< 160 degrees C) is implemented in the entire fabrication process, our detector is promising for monolithic integration with Si readout integrated circuits.

Towards a Ge-based laser for CMOS applications

We report experimental observation of direct band gap photoluminescence (PL) and optical bleaching of band-engineered epitaxial Ge-on-Si at room temperature, confirming that this material is a promising candidate for efficient light emitting devices on Si.

Substitutionality of Ge atoms in ion implanted AlSb

The substitution of Ge atoms into ion implanted AlSb is investigated by extended x‐ray absorption fine structure spectroscopy. Our results reveal that in the as‐implanted material, the implanted Ge atoms are equally distributed between two specific sites, one surrounded by Al atoms and the other surrounded by Sb atoms. After annealing at 750 °C for 5 s, the coordination number of the Ge atoms increases from ∼3 to ∼4 indicating solid phase regrowth of the implantation induced amorphous surface layer. Moreover, in the annealed AlSb, the substitution of Ge atoms into the Al sublattice dominates with an estimated GeAl]:[GeSb]∼0.8:0.2. These results suggest that Ge atoms act preferentially as donor species in AlSb.

Room-temperature oxygen sensitization in highly textured, nanocrystalline PbTe films: A mechanistic study

In this paper, we report large mid-wave infrared photoconductivity in highly textured, nanocrystalline PbTe films thermally evaporated on Si at room temperature. Responsivity as high as 25 V/W is measured at the 3.5 μm wavelength. The large photoconductivity is attributed to the oxygen incorporation in the films by diffusion. Carrier concentration as low as 1017 cm−3 is identified to be the consequence of Fermi level pinning induced by the diffused oxygen. The successful demonstration of IR-sensitive PbTe films without the need for high-temperature processing presents an important step toward monolithic integration of mid-wave PbTe infrared detectors on Si read-out integrated circuits (ROICs).

Persistent holographic absorption gratings in AlSb:Se

Photoquenching of DX‐like defects in heavily doped AlSb:Se is used to write persistent volume absorption holograms. Read‐out diffraction efficiencies of ∼0.5% were observed in samples 280 μm thick. The optical gratings are metastable, and semipermanent at liquid nitrogen temperatures, and are reversibly erased by heating the crystal above 140 K. The activation energy of regeneration of the stable DX state is obtained by measuring the decay times of the diffracted signal for temperatures between 100 and 116 K. We obtain a regeneration energy of 180 meV. Larger regeneration energies are important for eventual application of this material class to holographic optical memories.

On-chip chalcogenide glass waveguide-integrated mid-infrared PbTe detectors

We experimentally demonstrate an on-chip polycrystalline PbTe photoconductive detector integrated with a chalcogenide glass waveguide. The device is monolithically fabricated on silicon, operates at room-temperature, and exhibits a responsivity of 1.0 A/W at wavelengths between 2.1 and 2.5 μm.

Advanced infrared photonic devices based on HgMnTe

This review is oriented toward practical technological aspects of growth and applications of narrow bandgap semimagnetic semiconducting HgMnTe alloys. It summarizes recent achievements in crystal growth, device fabrication, and device characterization. Current work is focused on analyses of the growth process, approaches for the achievement of improved composition uniformity, the relationship between material properties and device performance, a comparison of performance of HgMnTe and HgCdTe devices, and new magnetic exchanged- based IR devices.