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Pure semiconductor tungsten oxide (WO 3 ), indium oxide (In 2 O 3 ) and mixed nanocomposites with different WO 3 to In 2 O 3 ratios were successfully synthesized by simple sol-gel method following calcination at 600 °C. The morphology, phase composition and features of crustal structure of the materials were studied by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transition electron microscopy and electron paramagnetic resonance spectroscopy. It was found that the nanocomposite materials are characterized by fine crystallinity of 8–38 nm, highly defective crystal cells and presence of delocalized electrons in their structures, which can significantly affect gas sensitivity. The gas sensors based on WO 3 –In 2 O 3 composite structures exhibited excellent CO and NO 2 detecting performance at optimal operating temperature of ∼240 °C and ∼140 °C, respectively. © 2019, QC 20201008

Epitaxial lateral overgrowth (ELOG) of GaInP on GaAs by hydride vapor phase epitaxy (HVPE) is carried out as a pre-study to obtain GaInP/Si heterointerface. We present first results on the growth of GaInP/Si by a modified ELOG technique, corrugated epitaxial lateral overgrowth (CELOG)., QC 20170307

We report in detail on the luminescence imaging setup developed within the last years in our laboratory. In this setup, the luminescence emission of silicon solar cells or silicon wafers is analyzed quantitatively. Charge carriers are excited electrically (electroluminescence) using a power supply for carrier injection or optically (photoluminescence) using a laser as illumination source. The luminescence emission arising from the radiative recombination of the stimulated charge carriers is measured spatially resolved using a camera. We give details of the various components including cameras, optical filters for electro- and photo-luminescence, the semiconductor laser and the four-quadrant power supply. We compare a silicon charged-coupled device (CCD) camera with a back-illuminated silicon CCD camera comprising an electron multiplier gain and a complementary metal oxide semiconductor indium gallium arsenide camera. For the detection of the luminescence emission of silicon we analyze the dominant noise sources along with the signal-to-noise ratio of all three cameras at different operation conditions. © 2011 American Institute of Physics.

Magnetotransport properties of GaMnAsInGaAsGaMnAs trilayer structures have been investigated by Hall measurements. The samples in the series are identical except for the InGaAs spacer thickness, which varies from 5 to 50 nm. The Hall measurements revealed the systematic change of magnetic easy axes from in-plane to out-of plane with increasing InGaAs spacer thickness. Such dependence of magnetic easy axes of the trilayer systems was understood in terms of the magnetic anisotropy change with spacer thickness. In the magnetization reversal process, various configurations of magnetization between the two GaMnAs layers were observed both in in-plane and out-of plane samples by the planar and the anomalous Hall effects. © 2009 American Institute of Physics., References: Baibich, M.N., Broto, J.M., Fert, A., Vandau, F.N., Petroff, F., Eitenne, P., Creuzet, G., Chazelas, J., (1988) Phys. Rev. Lett., 61, p. 2472; Binasch, G., Grunberg, P., Saurenbach, F., Zinn, W., (1989) Phys. Rev. B, 39, p. 4828; Parkin, S.S.P., Roche, K.P., Samant, M.G., Rice, P.M., Beyers, R.B., Scheuerlein, R.E., O'Sullivan, E.J., Gallagher, W.J., (1999) J. Appl. Phys., 85, p. 5828; Ohno, H., Chiba, D., Matsukura, F., Omiya, T., Abe, E., Dietl, T., Ohno, Y., Ohtani, K., (2000) Nature (London), 408, p. 944; Lee, S., Chung, S.J., Choi, I.S., Yuldeshev, S.U., Im, H., Kang, T.W., Lim, W.L., Furdyna, J.K., (2003) J. Appl. Phys., 93, p. 8307; Koshihara, S., Oiwa, A., Hirasawa, M., Katsumoto, S., Iye, Y., Urano, C., Takagi, H., Munekata, H., (1997) Phys. Rev. Lett., 78, p. 4617; Chung, S.J., Lee, S., Park, I.W., Liu, X., Furdyna, J.K., (2004) J. Appl. Phys., 95, p. 7402; Chung, S.J., Shin, D.Y., Kim, H., Lee, S., Liu, X., Furdyna, J.K., (2008) J. Electron. Mater., 37, p. 912; Xiang, G., Sheu, B.L., Zhu, M., Schiffer, P., Samarth, N., (2007) Phys. Rev. B, 76, p. 035324; Ge, Z., Zhou, Y.Y., Cho, Y.J., Liu, X., Furdyna, J.K., Dobrowolska, M., (2007) Appl. Phys. Lett., 91, p. 152109; Shen, A., Ohno, H., Matsukura, F., Sugawara, Y., Akiba, N., Kuroiwa, T., Oiwa, A., Iye, Y., (1997) J. Cryst. Growth, 175, p. 1069; Abolfath, M., Jungwirth, T., Brum, J., MacDonald, A.H., (2001) Phys. Rev. B, 63, p. 054418; Dietl, T., Ohno, H., Matsukura, F., (2001) Phys. Rev. B, 63, p. 195205; Stoner, E.C., Wohlfarth, E.P., (1948) Philos. Trans. R. Soc. London, Ser. A, 240, p. 74; Farle, M., (1998) Rep. Prog. Phys., 61, p. 755; Son, H., Chung, S.J., Yea, S.Y., Lee, S., Liu, X., Furdyna, J.K., (2008) J. Appl. Phys., 103, pp. 07F313QC 20130513

We present an experimental study of the main modes involved in the emission properties of InGaAs-GaAs quantum-well oxide-confined long wavelength vertical-cavity surface-emitting lasers. Lasing properties are dominated by the so-called "oxide modes" and by aperture modes, respectively, for small and large driving currents. We present complementary investigations of the laser emission including far-field angular distribution and spectroscopic near-field optical microscopy to a better understanding of the nature of the "oxide modes.", QC 20120305

In this Letter, the first spin noise spectroscopy measurements in semiconductor systems of reduced effective dimensionality are reported. The nondemolition measurement technique gives access to the otherwise concealed intrinsic, low temperature electron spin relaxation time of n-doped GaAs (110) quantum wells and to the corresponding low temperature anisotropic spin relaxation. The Brownian motion of the electrons within the spin noise probe laser spot becomes manifest in a modification of the spin noise line width. Thereby, the spatially resolved observation of the stochastic spin polarization uniquely allows to study electron dynamics at equilibrium conditions with a vanishing total momentum of the electron system. © 2008 The American Physical Society.

A controlled method of manipulation of nanowires was found using the tip of an Atomic Force Microscope (AFM). Manipulation is done in the ‘Retrace Lift’ mode, where feedback is turned off for the reverse scan and the tip follows a nominal path. The effective manipulation force during the reverse scan can be changed by varying an offset in the height of the tip over the surface. Using this method, we have studied InAs nanowires on different substrates. We have also investigated interactions between wires and with gold features patterned onto the substrates.

A controlled method of manipulation of nanowires was found using the tip of an Atomic Force Microscope (AFM). Manipulation is done in the ‘Retrace Lift’ mode, where feedback is turned off for the reverse scan and the tip follows a nominal path. The effective manipulation force during the reverse scan can be changed by varying an offset in the height of the tip over the surface. Using this method, we have studied InAs nanowires on different substrates. We have also investigated interactions between wires and with gold features patterned onto the substrates.

It was shown experimentally that charging InAs quantum dots (QDs) embedded in a small-area GaAs/AlAs double-barrier resonant tunneling diode (RTD) effectively modified the carrier transport properties of the RTD. By adopting and comparing the one-dimensional plane-wave and three-dimensional (3D) wave-packet transport theories we show that the electron transports in the QDRTD device are in the form of 3D wave packets, which are strongly affected by the 3D long-range Coulomb potential induced by charged InAs QDs. This explains well experimental data and indicates that the 3D wave-packet transport model is more appropriate for the QDRTD device., QC 20100902. Uppdaterad från In press till Published (20100902)

The what-if analysis process is essential in symbiotic simulation systems. It is responsible for creating a number of alternative what-if scenarios and evaluating their performance by means of simulation. Most applications use a reactive approach for triggering the what-if analysis process. In this paper we describe a preventive triggering approach which is based on the detection of a future critical condition in the forecast of a physical system. With decreasing probability of a critical condition, using preventive what-if analysis becomes undesirable. We introduce the notion of a Gvalue and explain how this metric can be used to decide whether or not to use preventive what-if analysis. In addition, we give an example for a possible application in semiconductor manufacturing., QC 20141015

A controlled method of manipulation of nanowires was found using the tip of an Atomic Force Microscope (AFM). Manipulation is done in the ‘Retrace Lift’ mode, where feedback is turned off for the reverse scan and the tip follows a nominal path. The effective manipulation force during the reverse scan can be changed by varying an offset in the height of the tip over the surface. Using this method, we have studied InAs nanowires on different substrates. We have also investigated interactions between wires and with gold features patterned onto the substrates.

In this article, we report on long wavelength (1.27 ÎŒm) single-mode micro-structured photonic crystal strained InGaAs quantum wells VCSELs for optical interconnection applications. Single fundamental mode room-temperature continuous-wave lasing operation was demonstrated for devices designed and processed with different two-dimensional etched patterns. The conventional epitaxial structure was grown by Metal-Organic Vapor Phase Epitaxy (MOVPE) and contains fully doped GaAs/AlGaAs DBRs, one oxidation layer and three strained InGaAs quantum wells. The holes were etched half-way through the top-mirror following various designs (triangular and square lattices) and with varying hole's diameters and pitches. We obtained up to 1.7 mW optical output power and more than 30 dB Side-Mode Suppression Ratio (SMSR) at room temperature and in continuous wave operation. Systematic static electrical, optical and spectral characterization was performed on wafer using an automated probe station. Numerical modeling using the MIT Photonic-Bands (MPB [1]) package of the transverse modal behaviors in the photonic crystal was performed using the plane wave method in order to understand the index-guiding effects of the chosen patterns, and to further optimize the design structures for mode selection at the given wavelength., QC 20120228

GaAs-based VCSELs emitting near 1.3 Όm are realized using highly strained InGaAs quantum wells and a large detuning of the cavity resonance with respect to the gain peak. The VCSELs have an oxide aperture for current and optical confinement and an inverted surface relief for suppression of higher-order transverse modes. The inverted surface relief structure also has the advantage of suppressing oxide modes that otherwise appear in VCSELs with a large detuning between the cavity resonance and the gain peak. Under large signal, digital modulation, clear and open eyes and error free transmission over 9 km of single mode fiber have been demonstrated at the OC-48 and 10 GbE bit rates up to 85°C. Here we review these results and present results from a complementary study of the RF modulation characteristics, including second order harmonic and third order intermodulation distortion, relative intensity noise (RIN), and spurious free dynamic range (SFDR). RIN levels comparable to those of single mode VCSELs emitting at 850 nm are demonstrated, with values from -140 to -150 dB/Hz. SFDR values of 100 and 95 dB·Hz2/3 were obtained at 2 and 5 GHz, respectively, which is in the range of those required in radio-over-fiber systems., QC 20120301

A controlled method of manipulation of nanowires was found using the tip of an Atomic Force Microscope (AFM). Manipulation is done in the ‘Retrace Lift’ mode, where feedback is turned off for the reverse scan and the tip follows a nominal path. The effective manipulation force during the reverse scan can be changed by varying an offset in the height of the tip over the surface. Using this method, we have studied InAs nanowires on different substrates. We have also investigated interactions between wires and with gold features patterned onto the substrates.

A controlled method of manipulation of nanowires was found using the tip of an Atomic Force Microscope (AFM). Manipulation is done in the ‘Retrace Lift’ mode, where feedback is turned off for the reverse scan and the tip follows a nominal path. The effective manipulation force during the reverse scan can be changed by varying an offset in the height of the tip over the surface. Using this method, we have studied InAs nanowires on different substrates. We have also investigated interactions between wires and with gold features patterned onto the substrates.

A controlled method of manipulation of nanowires was found using the tip of an Atomic Force Microscope (AFM). Manipulation is done in the ‘Retrace Lift’ mode, where feedback is turned off for the reverse scan and the tip follows a nominal path. The effective manipulation force during the reverse scan can be changed by varying an offset in the height of the tip over the surface. Using this method, we have studied InAs nanowires on different substrates. We have also investigated interactions between wires and with gold features patterned onto the substrates.