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We report design, growth, and characterization of midwavelength infrared nBn photodetectors based on a type-II InAs/InAs1-xSbx superlattice on a GaSb substrate grown by metal-organic chemical vapor deposition. An InAs/AlAs1-ySby/InAs/InAs1-xSbx superlattice design was used as the large bandgap electron barrier in the photodetectors. At 150 K, the photodetector exhibits a peak responsivity of 1.23 A/W, corresponding to a quantum efficiency of 41% at an applied bias voltage of −100 mV under front-side illumination, with a 50% cut-off wavelength of 4.6 μm. With an R × A of 356 Ω cm2 and a dark current density of 1.6 × 10−4 A/cm2 under an applied bias of −100 mV at 150 K, the photodetector exhibits a specific detectivity of 1.4 × 1011 cm Hz1/2/W. [ABSTRACT FROM AUTHOR]

We report the growth and characterization of mid-wavelength infrared type-II InAs/InAs1−xSbx superlattice photodiodes on GaSb substrates grown by metal-organic chemical vapor deposition. At 150 K, the 50% cut-off wavelength is 5.0 μm, the dark current density is 3.3 × 10−4 A/cm2 under −20 mV bias, and the peak responsivity is 1.76 A/W corresponding to a quantum efficiency of 55% without anti-reflection coating. A specific detectivity of 1.2 × 1011 cm Hz1/2/W is achieved at 4.0 μm under −20 mV bias at 150 K. [ABSTRACT FROM AUTHOR]

Monolithic integration of antimonide (Sb)-based compound semiconductors on Si is in high demand to enrich silicon photonics by extending the detection range to longer infrared wavelengths. In this paper, we have demonstrated the damage-free transfer of large-area (1×1 cm 2) narrow-bandgap Sb-based type-II superlattice (T2SL)-based thin-film materials onto a Si substrate using a combination of wafer-bonding and chemical epilayer release techniques. An array of Sb-based T2SL-based long-wavelength infrared (LWIR) photodetectors with diameters from 100 to 400 μm has been successfully fabricated using standard "top-down" processing technique. The transferred LWIR photodetectors exhibit a cut-off wavelength of ~8.6 μm at 77 K. The dark current density of the transferred photodetectors under 200 mV applied bias at 77 K is as low as 5.7×10 -4 A/cm 2 and the R×A reaches 66.3 Ω·cm 2, exhibiting no electrical degradation compared with reference samples on GaSb native substrate. The quantum efficiency and peak responsivity at 6.75 μm (@77 K, 200 mV) are 46.2% and 2.44 A/W, respectively. The specific detectivity (D*) at 6.75 μm reaches as high as 1.6×10 11 cm·Hz1/2 /W under 200 mV bias at 77 K. Our method opens a reliable pathway to realize high performance and practical Sb-based optoelectronic devices on a Si platform. [ABSTRACT FROM AUTHOR]

We report the demonstration of high-performance long-wavelength infrared (LWIR) nBn photodetectors based on InAs/InAs1-xSbx type-II superlattices. A new saw-tooth superlattice design was used to implement the electron barrier of the photodetectors. The device exhibited a cut-off wavelength of ~10 μm at 77 K. The photodetector exhibited a peak responsivity of 2.65 A/W, corresponding to a quantum efficiency of 43%. With an R X A of 664 Ωcm2 and a dark current density of 8 X 10-5 A/cm2, under -80 mV bias voltage at 77 K, the photodetector exhibited a specific detectivity of 4.72 X 1011 cm√Hz/W and a background-limited operating temperature of 110 K. [ABSTRACT FROM AUTHOR]

The thermal treatment method was employed to prepare nickel-cobalt oxide (NiO/Co3O4) nanoparticles. This method was attempted to achieve the higher homogeneity of the final product. Specimens of nickel-cobalt oxide were characterized by various experimental techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). X-ray diffraction results showed that there was no crystallinity in the predecessor, and it still had the amorphous phase. The formations of the crystalline phases of the nickel-cobalt oxide nanoparticles started from 350-500 °C, and the final products had different crystallite sizes ranging from 11-35 nm. Furthermore, the variation of DC conductivity (σdc), impedance, tangent loss (tgδ) and dielectric constant (ε') of the calcined specimens with frequency in the range of 10²-106 Hz was investigated. σdc showed a value of 1.9 × 10-6 S/m, 1.3 × 10-6 S/m and 1.6 × 10-6 S/m for the specimens calcined at 350, 400 and 450 °C, respectively. Additionally, a decrease in tgσ values with an increase in temperature was observed. Finally, the formed nanoparticles exhibited ferromagnetic behaviors, which were confirmed by using a vibrating sample magnetometer (VSM). [ABSTRACT FROM AUTHOR]

The fabrication of Double gate (DG) and Single gate (SG) Junctionless silicon nanowire transistor (JLSNWT) was investigated in this research. The transistors used silicon nanowire patterned on lightly doped (105 cm-3) p-type silicon-on-insulator (SOI) wafer fabricated with an atomic force microscope (AFM) nanolithography technique. The top Si layer has a thickness of 90 nm and a resistivity (p) of 13.5-22.5 Ω cm. The modified RCA method implemented for sample preparation. The local anodic oxidation (LAO) followed by two wet etching steps, KOH etching for Si removal and HF etching for oxide removal, have implemented to reach the structures. The writing speed and applied tip voltage were held in 0.6 μm/s and 8.5 volt respectively. Scan speed was held in 1.0 |im/s. The etching processes were elaborately optimized by 30% wt. KOH + 10% vol. IPA in appropriate time, temperature and humidity. The structure is a gated resistor turned off based on a pinch-off effect principle, when essential positive gate voltage is applied and made a sufficiently large barrier in the gating region. Negative gate voltage is unable to make significant effect on drain current to drive the device into accumulation mode. [ABSTRACT FROM AUTHOR]

A multi-gate n-type In0.53Ga0.47As MOSFET is fabricated using gate-first self-aligned method and air-bridge technology. The devices with different gate lengths were fabricated with the Al2O3 oxide layer with the thickness of 8 nm. In this letter, impact of gate length variation on device parameter such as threshold voltage, high and low voltage transconductance, subthreshold swing and off current are investigated at room temperature. Scaling the gate length revealed good enhancement in all investigated parameters but the negative shift in threshold voltage was observed for shorter gate lengths. The high drain current of 1.13 A/mm and maximum extrinsic transconductance of 678 mS/mm with the field effect mobility of 364 cm2/Vs are achieved for the gate length and width of 0.2 µm and 30µm, respectively. The source/drain overlap length for the device is approximately extracted about 51 nm with the leakage current in order of 10−8 A. The results of RF measurement for cut-off and maximum oscillation frequency for devices with different gate lengths are compared. [ABSTRACT FROM AUTHOR]

Zinc sulphide (ZnS) nanoparticles were synthesized via simple, rapid and energy efficient microwave technique. The obtained nanoparticles were found to possess a cubic structure with an average particle size of less than 5 nm. By changing the microwave irradiationtime from 5 to 30 min, the average size of nanoparticles increased and a broader size distribution was obtained. The degree of crystallinity also increased with increasing irradiation time and reached to maximum at 25 min and then fell by rising further the irradiation time. The absorption spectra of prepared ZnS nanoparticles revealed a blue shift in the band gap energy with respect to the bulk counterpart owing to the quantum confinement effect. The photoluminescence study showed the emission intensity increased with increasing the irradiation time up to 25 min due to the increment in crystallinity of the obtained nanoparticles. Further study indicated that the microwave irradiation time has also influenced the electrical properties of nanoparticles, so that the DC conductivity increased from 1.08×10-6 to 1.67×10-4 S/m for irradiation time of 5-25min and decreased to 1.74×10-6 S/m for further irradiation time at 30 min. The dielectric constant showed a power law dispersion with no observed peak for all samples with different irradiation times. [ABSTRACT FROM AUTHOR]