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A 16-channel monolithically integrated index-coupled distributed-feedback laser array has been fabricated using nanoimprint technology. Selective lasing wavelengths with 300 and 100 GHz frequency space are obtained. The fine tenability for an individual laser in the array is achieved with a Ti-Au thin-film resistor integrated on the chip. The typical threshold current is between 10 and 15 mA without current in the thin-film resistor. The optical output power of each channel is about 6 mW at an injection current of 70 mA [ABSTRACT FROM AUTHOR]

A novel tunable laser with digital concatenated grating reflectors, which has a flatter envelope of reflection peaks, is designed and fabricated. The key concept of the approach is to utilize multi-sampled gratings which have different Bragg wavelengths and the same sampling period. The difference of each Bragg wavelength is integer multiple of the space between the peaks of sampled gratings. Here, nanoimprint lithographic technology is used to fabricate the complex gratings. The typical threshold current of the tunable laser is 34 mA, and the tuning range is larger than 32 nm. The non-uniformity of the output power is less than 2 dB. [ABSTRACT FROM AUTHOR]

In this paper we report the superconductivity above 40 K in the electron doping single crystals Ca1−xRxFe2As2 (R = La, Ce, Pr). The x-ray diffraction patterns indicate high crystalline quality and c-axis orientation. The resistivity anomaly in the parent compound CaFe2As2 is completely suppressed by partial replacement of Ca with rare-earth elements and the superconducting transition reaches as high as 46 K, which is higher than the value in electron doping FeAs-122 compounds formed by substituting Fe ions with transition metal, and even surpasses the highest value observed in hole doping systems with a transition temperature up to 38 K. The upper critical fields have been determined with the magnetic field along the ab-plane and c-axis, yielding an anisotropy of 2–3. Hall effect measurements indicate that the conduction in this material is dominated by electron-like charge carriers. Our results confirm the feasibility of inducing superconductivity in Ca122 compounds via electron doping using aliovalent rare-earth substitution into the alkaline earth site, which should add more ingredients to the underlying physics of the iron-based superconductors. [ABSTRACT FROM AUTHOR]

In this paper, we successfully demonstrated a high quality p-Si/n-GaN heterojunction diode through van der Waals bonding implemented by nanomembrane lift-off and transfer-print technique. A nanoscale native oxide layer is observed at the interface by transmission electron microscope, which plays a role as passivation-layer. The heterojunction diode has excellent electrical performance with a high rectification ratio of 4.75 × 105 at V and a low reverse dark current density of 4.03 × 10–4 A cm−2 at −3 V. In addition, the heterojunction diode responds to both near ultraviolet (375.6 nm) and red light (650 nm) with responsivity of 429.9 mA W−1 and 66.8 mA W−1 (at −3 V) respectively. This result indicates that a large-lattice-mismatched semiconductor heterojunction can be fabricated based on GaN by using transfer-print technique, thereby expanding the operating band of GaN-based detectors from ultraviolet region to visible region. [ABSTRACT FROM AUTHOR]

The conventional D flip flop (DFF) consists of six pseudo-CMOS NOR gates integrated by monotype transistors. By analyzing the six logic states of the conventional DFF, it is found that the three-input NOR gate can be replaced by a new three-input NOR gate with a pull-up control signal and the pull-up control signal is connected to an output of another NOR gate. As a result, a new DFF is developed by using such an internal feedback control method. The static power consumption can be reduced by cutting off the dc path properly in the proposed DFF. For comparison, the conventional DFF and the proposed DFF are both fabricated by metal oxide thin film transistors with an etch stop layer structure on the basis of the same design parameters. Both the conventional DFF and the proposed DFF have the same function and both work using the negative edge triggered method. The measured power consumption of the proposed DFF is at least 13% less than that of the conventional DFF under the condition of a 20 kHz clock signal. [ABSTRACT FROM AUTHOR]

This paper proposes a new gate driver employing only a single negative power source, which is integrated by In-Zn-O TFTs with an etch stop layer (ESL) structure. A negative voltage generating module (NVGM) is developed to generate a lower voltage level than that of the negative power source, in order to completely shut down the pull-down transistors of the output module. 30 stages of the proposed gate driver are fabricated on glass substrate. It is shown that the gate driver successfully achieves full swing output signals at different clock frequencies (6.67 kHz, 66.7 kHz) and negative power sources (−4 V, −5 V, −6 V) with resistive load RL = 3 kΩ and capacitive load CL = 30 pF. The measured power consumption per stage of the proposed gate driver is 101 μW at the clock frequency of 66.7 kHz. [ABSTRACT FROM AUTHOR]

An Al-based ohmic process assisted by an inductively coupled plasma (ICP) recess treatment is proposed for AlGaN/GaN heterostructure field-effect transistors (HFETs) to realize ohmic contact, which is only needed to anneal at 500 °C. The recess treatment was done with SiCl4 plasma with 100 W ICP power for 20 s and annealing at 575 °C for 1 min. Under these conditions, contact resistance of 0.52 Ωmm was confirmed. To suppress the ball-up phenomenon and improve the surface morphology, an Al/TiN structure was also fabricated with the same conditions. The contact resistance was further improved to 0.30 Ωmm. By using this plasma-assisted ohmic process, a gate-first HFET was fabricated. The device showed high drain current density and high transconductance. The leakage current of the TiN-gate device decreased to 10−9 A, which was 5 orders of magnitude lower than that of the device annealed at 800 °C. The results showed that the low-temperature ohmic contact process assisted by ICP treatment is promising for the fabrication of gate-first and self-aligned gate HFETs. [ABSTRACT FROM AUTHOR]

Using Zn(NO3)2, H2SeO3 and graphene oxide as precursors, the zinc oxide/selenium/reduced graphene oxide (ZnO/Se/RGO) composite was facilely electrodeposited on the surface of indium tin oxide glass. The conditions for electrochemical synthesis such as electrodeposition potential and electrolyte composition were studied. The morphology and crystallization of the products as-prepared were characterized using scanning electron microscopy (SEM) and x-ray diffractometry (XRD) respectively. The light absorption and conductivity of the products were studied by UV-visible spectroscopy (UV-vis) and electrochemical impedance spectroscopy (EIS). Based on a series of experimental results, the photoelectrical conversion mechanism and effect factors of the products were explored. By means of synergistic action of n-type ZnO, p-type Se and conductive RGO, the ZnO/Se/RGO composite showed excellent photoelectric conversion under visible light irradiation. [ABSTRACT FROM AUTHOR]