Xin Zhou,†,‡ Songyi Lee,† Zhaochao Xu,* and Juyoung Yoon*,† †Department of Chemistry and Nanoscience, Ewha Womans University, Seoul 120-750, Republic of Korea ‡Research Center for Chemical Biology, Department of Chemistry, Yanbian University, Yanjii 133002, People’s Republic of China Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Shahekou, Dalian, Liaoning, People’s Republic of China

Recent Progress on the Development of Chemosensors for Gases.

Synthesis of highly-ordered TiO2 nanotubes for a hydrogen sensor

Semiconductor science and technology (S T) is a very active branch in the field of natural science, and is also a typical example embodying the development of advanced S T. The Nobel prize for physics is a prize of the highest honour in the world, and there are certain relationships between this award and semiconductor S T. We explore and analyze these inherent relationships which have practical importance for our understanding of the development of semiconductor S T and for predicting its future.

Semiconductor science and technology, and Nobel physics prizes

III-V semiconductors, GaAs and in particular InGaP, are used in many different electronic applications, such as high power and high frequency devices, laser diodes and high brightness LED. Their direct bandgap and high reliability make them ideal candidates for the realisation of high efficiency solar cells: in the past years they have been successfully used as power sources for satellites in space, where they are able to produce electricity from sunlight with an overall efficiency of around 30%. Nowadays, the use of arsenides and phosphides as photovoltaic (PV) devices is confined only to space applications since their price is much higher than conventional Si flat panel modules, the leading PV market technology. But with the introduction of multijunction solar cells capable of operating in high concentration solar light, the area and, therefore, the cost of these cells can be reduced and will eventually find an application and market also on Earth. This article will review the situation of semiconductor solar cell materials, focusing on Si, GaAs, InGaP and multijunction solar cells and will discuss future trends and possibilities of bringing III-V technology from space to Earth. Copyright © 2006 John Wiley & Sons, Ltd.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pip.715

The potential of III-V semiconductors as terrestrial photovoltaic devices

Over the past few decades the fabrication of nanoscale materials for use in chemical sensing, biomedical and biological analyses has proven a promising avenue. Nanomaterials show promise in such chemical and biological analysis mainly due to their highly tunable size- and shape-dependent chemical and physical properties. Furthermore, they exhibit unique surface chemistry, thermal stability, high surface area and large pore volume per unit mass that can be exploited for sensor fabrication. This review will discuss the chemical and physical properties of nanomaterials necessary for use as chemosensors and biosensors. It will also highlight some noteworthy recent avenues using nanoscale materials as scaffolds for chemosensing and biosensing. Nanomaterials that have proven to be useful for the fabrication of sensors, as reviewed herein, have compositions including metals, metal oxides, chalcogenides and polymers. Their structures range from nanoparticles, nanorods, and nanowires to nanoporous and core-shells. Examples of the different types of structures and compositions as well as sensors and biosensors fabricated from them will be described. Some nanomaterials are functionalized with various kinds of ligands and bioactive groups to produce sensitive and selective sensors for specific analytes. The combination of two or more types of nanostructures with core-shell type nanoassemblies and other composite structures, in addition to advantageous features enhancing sensitivity and response time of related sensors, are also discussed.

Recent advances in nanostructured chemosensors and biosensors

Comprehensive investigation on planar type of Pd–GaN hydrogen sensors

Fabrication of n/sup +/-GaAs//spl delta/(P/sup +/)-GaInP/n-GaAs heterojunction camel-gate field-effect transistors by LP-MOCVD is reported The active channel was tri-step doped to obtain a high-barrier camel diode A /spl delta/(P/sup +/)-GaInP layer was employed to offer a high valence band offset as a hole barrier, as well as an enhanced conduction band offset for good electron confinement A camel diode using this material structure shows a barrier height >12 eV and a very high breakdown voltage of 33 V The measured transconductance is 140 mS/mm with a unity current gain frequency of 17 GHz for a 1/spl times/50 /spl mu/m/sup 2/ device

Improved breakdown in LP-MOCVD grown n+-GaAs/(P+)-GaInP/n-GaAs heterojunction camel-gate FET

An N-Al/sub 0.5/Ga/sub 0.5/As/n-GaAs heterostructure-emitter bipolar transistor (HEBT), grown by MBE, has been fabricated with improved performance. The Al/sub 0.5/Ga/sub 0.5/As layer with higher valence-band offset Delta E/sub v/ offers better confinement of minority carriers (holes). A small offset voltage of about 80 mV and a high common-emitter current gain of 180 were measured for large-area devices. On the other hand, the adequate design of an n-GaAs emitter layer also plays an important role in device performance. The strongly knee-shaped characteristics and reachthrough effect were observed in those devices fabricated with 12 a thin n-GaAs emitter layer. >

An improved heterostructure-emitter bipolar transistor (HEBT)

This paper reports on a new Pd/GaN hydrogen sensor with two multi-finger Schottky contacts (named metal–semiconductor–metal (MSM) hydrogen sensor). Effects of hydrogen absorption on the MSM sensor are investigated. In addition to comparisons of sensing mechanism between metal–semiconductor (MS) and MSM sensors, related current–voltage characteristics, sensor responses, Schottky barrier height variations, response transients, and switching behaviors are included. Experimentally, symmetrically bi-directional sensing performances are obtained in the newly designed MSM sensor, resulting in both widespread forward- and reverse-voltage-operating regimes. When the MSM sensor is measured in a 1080 ppm H2/N2 ambience, the voltage-independent response and barrier-height variation obtained are 51 and 102 mV, respectively. Furthermore, the measured response time is as short as 38 ± 2 s. Together with good switching behaviors, the MSM sensor studied is a promising candidate as a high-performance hydrogen sensor being easily integrated with other devices.

Comprehensive study of Pd/GaN metal-semiconductor-metal hydrogen sensors with symmetrically bi-directional sensing performance

In this paper, a novel InGaP/GaAs multiple S-shaped negative-differential-resistance (NDR) switch based on a heterostructure-emitter bipolar transistor (HEBT) structure is fabricated and demonstrated. An interesting multiple NDR phenomenon resulting from an avalanche multiplication and successive two-stage barrier lowering process is observed under the inverted operation mode. The three-terminal-controlled and temperature-dependent NDR characteristics are also investigated. In addition, a typical transistor performance is found under the normal operation mode. Consequently, owing to the presented different stable operation points and transistor action, the studied device shows a good potential for multiple-valued logic and analog amplification circuit applications.

Wen-Shiung Lour

Papers

Comprehensive investigation on planar type of Pd–GaN hydrogen sensors

Improved breakdown in LP-MOCVD grown n+-GaAs/(P+)-GaInP/n-GaAs heterojunction camel-gate FET

An improved heterostructure-emitter bipolar transistor (HEBT)

Comprehensive study of Pd/GaN metal-semiconductor-metal hydrogen sensors with symmetrically bi-directional sensing performance

A novel InGaP/GaAs S-shaped negative-differential-resistance (NDR) switch for multiple-valued logic applications