Takeshi Aoki

Photoluminescence lifetime distribution of a-Si:H and a-Ge:H expanded to nanosecond region using wide-band frequency-resolved spectroscopy

Abstract We present the first survey on quadrature frequency-resolved spectroscopy (QFRS) spectra in the nanosecond (ns) region of photoluminescence (PL) of a-Si:H and a-Ge:H. Our QFRS study reveals that there is no evidence of a peak or shoulder for the ns PL lifetime component, and thus the PL lifetime distribution has basically a double-peak structure with two components of μs and ms lifetimes in both materials. The μs component in the lifetime distribution is enhanced at higher PL photon energy, which favors the exciton model. Generation rate ( G ) dependence of QFRS spectra shows a common feature, for both a-Si:H and a-Ge:H, where excitonic emission shifts to non-geminate radiative recombination as G increases.

Kinetic Inductance of Superconducting Coplanar Waveguides

An analytical expression for the kinetic inductance of the superconducting coplanar waveguide is given using the conformal mapping technique. This expression is shown to be in good agreement with experimental results obtained from the temperature dependence of the resonant frequency of the NbN coplanar waveguide resonators, especially in the case of a film thickness smaller than the magnetic penetration depth. It is also shown that the magnetic penetration depth of the superconducting thin films can be evaluated by this method.

Hydrogen dilution effects on properties of ECR plasma deposited a-Ge:H

Abstract Highly photoluminescent, photosensitive a-Ge:H films are prepared by decomposing H 2 -diluted GeH 4 in an ECR plasma reactor designed for minimizing microwave power reflection. Film qualities are not only dependent on H 2 -dilution but also on total gas flow rate. Samples prepared at high total flow rates are good in both optoelectronic and structural properties and this is interpreted in terms of hydrogen radical coverage and ion bombardment on the growing surface.

50.2: High Reliable In-Ga-Zn-Oxide FET Based Electronic Global Shutter Sensors for In-Cell Optical Touch Screens and Image Sensors

A 6 inch XGA LCD touch screen with optical sensors in its pixels, using oxide semiconductor (OS) FETs has been developed. The extremely low off-state current of the OS FET facilitates the use of a global shutter and leads to an improved accuracy of touch detection. The possibility of a novel application of a touch screen and an image sensor that is an application of the combination of OS FETs and global shutter is proposed.

Crystalline In?Ga?Zn?O FET-based configuration memory for multi-context field-programmable gate array realizing fine-grained power gating

A multi-context (MC) field-programmable gate array (FPGA) enabling fine-grained power gating (PG) is fabricated by a hybrid process involving a 1.0 ?m c-axis aligned crystalline In?Ga?Zn?O (CAAC-IGZO) field-effect transistor (FET), which is one of CAAC oxide-semiconductor (OS) FETs, and a 0.5 ?m complementary metal oxide semiconductor (CMOS) FET. The FPGA achieves a 20% layout area reduction in a routing switch and an 82.8% reduction in power required to retain data of configuration memory (CM) cells at 2.5 V driving compared to a static random access memory (SRAM)-based FPGA. A controller for fine-grained PG can be implemented at an area overhead of 7.5% per programmable logic element (PLE) compared to a PLE without PG. For each PLE, the power overhead with fine-grained PG amounts to 2.25 and 2.26 nJ for power-on and power-off, respectively, and break-even time (BET) is 19.4 ?s at 2.5 V and 10 MHz driving.

An Improved Optical Lever Technique for Measuring Film Stress

This letter describes a simple and accurate method of measuring film stress. This method differs principally from the conventional optical lever method in utilizing two parallel beams instead of translating a sample. The apparatus assembled experimentally demonstrates a detectable deflection of the sample on the order of 1 µm.

High-rate deposition of a-Si:H using electron cyclotron resonance plasma

Abstract Hydrogenated amorphous silicon(a-Si:H)films of device quality with high deposition rate up to 250A/s have been obtained from decomposition of SiH 4 H 2 mixture by using electron cyclotron resonance (ECR) plasma. Deposition rate, optoelectric properties and IR absorption spectra have been investigated against substrate temperature, SiH 4 fraction and microwave power.

Photoluminescence in high-quality a-Ge:H

We present quadrature frequency resolved spectroscopy (QFRS) measurements of photoluminescence (PL) in photoconductive and luminescent films of a-Ge:H with a defect density1 10 16 cm ˇ3 obtained from electron cyclotron resonance (ECR) plasma chemical vapor deposition (PCVD), together with a study of PL and PL excitation (PLE) spectra. A double-peak lifetime distribution is observed with a short lifetime at1 ls and a long one at0.1 ms as observed in a-Si:H. The dependence of the two lifetimes and their corresponding relative quantum eAciencies on the e‐h pair generation rate and temperature is also investigated. The occurrence of double peaks is attributed to the radiative recombination from singlet and triplet exciton states, and the exchange energy between singlet and triplet states is estimated to be3.3 meV in a-Ge:H. ” 2000 Published by Elsevier Science B.V. All rights reserved.

Photoluminescence lifetime distributions of chalcogenide glasses obtained by wide-band frequency resolved spectroscopy

Photoluminescence (PL) lifetime distributions for amorphous arsenic chalcogenides g-As2Se3 and g-As2S3, and amorphous selenium a-Se, are obtained for the first time using a quadrature frequency resolved spectroscopy (QFRS) technique modified for nanosecond resolution. The g-As2S3 and a-Se chalcogenides exhibit double-peak lifetime distributions, whereas the lifetime distribution of g-As2Se3 peaks uniquely at around 10−4 s, which is consistent with earlier results. PL fatigue is found to reduce the intensity of PL but not affect the observed PL lifetimes. A self-trapped exciton model is adopted to explain the experimental results, providing reasonable mechanisms for the two-component lifetimes and associated phenomena. For a-Se, singlet–triplet exchange energy of ≈160 meV is estimated.

Excitonic contribution to photoluminescence in amorphous semiconductors

Excitonic contribution to photoluminescence in amorphous semiconductors Jai Singh a , T. Aoki b & K. Shimakawa c a Faculty of Site B-28, Northern Territory University, Darwin, Northern Territory, 0909, Australia b Department of Electronics and Computer Engineering and Joint Research Center of High Technology, Tokyo Institute of Polytechnics, Atsugi, 243-0297, Japan c Department of Electrical and Electronic Engineering, Gifu University, Gifu, 501-1193, Japan