Browsing by Author "Lin, Yen-Fu"

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A Triode Device with a Gate Controllable Schottky Barrier: Germanium Nanowire Transistors and Their Applications
(1970-01-01)
Lin, Che-Yi
;
Chen, Chao-Fu
;
Chang, Yuan-Ming
;
Yang, Shih-Hsien
;
Lee, Ko-Chun
Electrical contacts often dominate charge transport properties at the nanoscale because of considerable differences in nanoelectronic device interfaces arising from unique geometric and electrostatic features. Transistors with a tunable Schottky barrier between the metal and semiconductor interface might simplify circuit design. Here, germanium nanowire (Ge NW) transistors with Cu3Ge as source/drain contacts formed by both buffered oxide etching treatments and rapid thermal annealing are reported. The transistors based on this Cu3Ge/Ge/Cu3Ge heterostructure show ambipolar transistor behavior with a large on/off current ratio of more than 10(5) and 10(3) for the hole and electron regimes at room temperature, respectively. Investigations of temperature-dependent transport properties and low-frequency current fluctuations reveal that the tunable effective Schottky barriers of the Ge NW transistors accounted for the ambipolar behaviors. It is further shown that this ambipolarity can be used to realize binary-signal and data-storage functions, which greatly simplify circuit design compared with conventional technologies.
Ambipolar MoTe2 Transistors and Their Applications in Logic Circuits
(2014-05-28)
Lin, Yen-Fu
;
Xu, Yong
;
Wang, Sheng-Tsung
;
Li, Song-Lin
;
Yamamoto, Mahito
We report ambipolar charge transport in a-molybdenum ditelluride (MoTe2) flakes, whereby the temperature dependence of the electrical characteristics was systematically analyzed. The ambipolarity of the charge transport originated from the formation of Schottky barriers at the metal/MoTe2 contacts. The Schottky barrier heights as well as the current on/off ratio could be modified by modulating the electrostatic fields of the back-gate voltage (V-bg) and drain-source voltage (V-ds). Using these ambipolar MoTe2 transistors we fabricated complementary inverters and amplifiers, demonstrating their feasibility for future digital and analog circuit applications.
Analog Circuit Applications Based on All-2D Ambipolar ReSe2 Field-Effect Transistors
(2019-05-01)
Lee, Ko-Chun
;
Yang, Shih-Hsien
;
Sung, Yung-Shang
;
Chang, Yuan-Ming
;
Lin, Che-Yi
Complementary circuits based on 2D materials show great promise for next-generation electronics. An ambipolar all-2D ReSe2 field-effect transistor (FET) with a hexagonal boron nitride gate dielectric is fabricated and its electronic characteristics are comprehensively studied by temperature dependence and noise measurements. Ambipolar transfer characteristics are achieved owing to the tunable Fermi level of the graphene contact and negligible and 30 meV Schottky barrier heights for the n- and p-channel regimes, respectively. An inverter is also fabricated to demonstrate ambipolar ReSe2 FET operation in a logic circuit. Furthermore, a p/n switchable unipolar FET is designed and shows potential for building complimentary circuits from a signal device. This work demonstrates the potential of all-2D ReSe2 FETs and makes available new approaches for designing next-generation devices.
Atomically thin van der Waals tunnel field-effect transistors and its potential for applications
(2019-03-08)
Yang, Shih-Hsien
;
Yao, You-Teng
;
Xu, Yong
;
Lin, Che-Yi
;
Chang, Yuan-Ming
Power dissipation is a crucial problem as the packing density of transistors increases in modern integrated circuits. Tunnel field-effect transistors (TFETs), which have high energy filtering provided by band-to-band tunneling (BTBT), have been proposed as an alternative electronics architecture to decrease the energy loss in bias operation and to achieve steep switching at room temperature. Very recently, the BTBT behavior has been demonstrated in van der Waals heterostructures by using unintentionally doped semiconductors. The reason of the BTBT formation is attributed to a significant band bending near the heterointerface, resulting in carrier accumulations. In this work, to investigate charge transport in type-III transistors, we adopted the same band-bending concept to fabricate van der Waals BP/MoS2 heterostructures. Through analyzing the temperature dependence of their electrical properties, we carefully ruled out the contribution of metal-semiconductor contact resistances and improved our understanding of carrier injection in 2D type-III transistors. The BP/MoS2 heterostructures showed both negative differential resistance and 1/f(2) current fluctuations, strongly demonstrating the BTBT operation. Finally, we also designed a TFET based on this heterostructure with an ionic liquid gate, and this TFET demonstrated an subthreshold slope can successfully surmount the thermal limit of 60 mV/decade. This work improves our understanding of charge transport in such layered heterostructures and helps to improve the energy efficiency of next-generation nanoscale electronics.
Broadband Omnidirectional Light Trapping in Gold-Decorated ZnO Nanopillar Arrays
(2017-04-05)
Chang, Yuan-Ming
;
Lin, Man-Ling
;
Lai, Tung-Yen
;
Chen, Chang-Hung
;
Lee, Hsin-Yi
The photoluminescence (PL) and reflectivity characteristics of zinc oxide nanopillars- (ZnO-NPs) grown on indium tin oxide (ITO)-coated glasses were investigated. The room temperature PL showed bright -white -light emission for the undoped ZnO-NPs grown at 600 degrees C, suggesting the close relation between the optical characteristic and "the growth conditions being, carried out for,obtaining the present ZnO-NPs. The reflectivity of the as -grown ZnO-NPs array was about, similar to 29% with the wavelength of the incident light ranging from 200 to 1800 nm. Nevertheless, the reflectance reduced significantly to less than 9.9% when a layer of gold (Au) was deposited on ZnO=NPg by sputtering for 5 min, corresponding to more than 65% reduction in Au -coated ZnQ-NPs (Au/ZnO-NPs). Moreover, the angle -resolved reflectance measurement's on the present Au/ZnO-NPs array show an omnidirectional light -trapping characteristic. These remarkable characteristics, broadband and omnidirectional light -trapping -of Ati/ZnO-NPs, are attributed to the extended effective optical path of the incident light due to subwavelength scattering resulting,from the presence of Au nanoparticics.
Contact to ZnO and intrinsic resistances of individual ZnO nanowires with a circular cross section
(2007-05-28)
Lin, Yen-Fu
;
Jian, Wen-Bin
;
Wang, C. P.
;
Suen, Yuen-Wuu
;
Wu, Zhong-Yi
Single crystalline ZnO nanowires (NWs) with a circular cross section and similar to 40 nm in diameter have been synthesized and utilized to fabricate two-contact ZnO NW devices. The electrical properties of the NW devices can be categorized into two classes according to the magnitude of their room-temperature resistances. I-V curves of low-resistance devices exhibit downward bending features and their temperature dependent resistances demonstrate thermal activation transport in the ZnO NWs. The high-resistance NW devices can be modeled as back-to-back Schottky contacts and the electron transport through the contacts reveals a variable-range-hopping mechanism. (C) 2007 American Institute of Physics.
Dielectrophoretic placement of quasi-zero-, one-, and two-dimensional nanomaterials into nanogap for electrical characterizations
(2012-08-01)
Lin, Yen-Fu
;
Chiu, Shao-Chien
;
Wang, Sheng-Tsung
;
Fu, Sheng-Kai
;
Chen, Chien-Hsiang
DEP is one of promising techniques for positioning nanomaterials into the desirable location for nanoelectronic applications. In contrast, the lithography technique is commonly used to make ultra-thin conducting wires and narrow gaps but, due to the limit of patterning resolution, it is not feasible to make electrical contacts on ultra-small nanomaterials for a bottom-up device fabrication. Thus, integrating the lithography and dielectrophoresis, a real bottom-up fabrication can be achieved. In this work, the device with the nanogap in between two nanofinger-electrodes is made using electron-beam lithography from top down and the ultra-small nanomaterials, such as colloidal PbSe quantum dots, polyaniline nanofibers, and reduced-graphene-oxide flakes, are placed in the nanogap by DEP from bottom up. The threshold electric field for the DEP placement of PbSe nanocrystals was roughly estimated to be about 8.3 x 104 V/cm under our experimental configuration. After the DEP process, several procedures for reducing contact resistances are attempted and measurements of intrinsic electron transport in versatile nanomaterials are performed. It is experimentally confirmed that electron transport in both PbSe nanocrystal arrays and polyaniline nanofibers agrees well with Prof. Ping Sheng's model of granular metallic conduction. In addition, electron transport in reduced-graphene-oxide flakes follows Mott's 2D variable-range-hopping model. This study illustrates an integration of the electron-beam lithography and the DEP techniques for a precise manipulation of nanomaterials into electronic circuits for characterization of intrinsic properties.
"Dielectrophoretic placement of quasi-zero-, one-, and two-dimensional nanomaterials into nanogap for electrical characterizations"
(2012-08-01)
Lin, Yen-Fu
;
Chiu, Shao-Chien
;
Wang, Sheng-Tsung
;
Fu, Sheng-Kai
;
Chen, Chien-Hsiang
"DEP is one of promising techniques for positioning nanomaterials into the desirable location for nanoelectronic applications. In contrast, the lithography technique is commonly used to make ultra-thin conducting wires and narrow gaps but, due to the limit of patterning resolution, it is not feasible to make electrical contacts on ultra-small nanomaterials for a bottom-up device fabrication. Thus, integrating the lithography and dielectrophoresis, a real bottom-up fabrication can be achieved. In this work, the device with the nanogap in between two nanofinger-electrodes is made using electron-beam lithography from top down and the ultra-small nanomaterials, such as colloidal PbSe quantum dots, polyaniline nanofibers, and reduced-graphene-oxide flakes, are placed in the nanogap by DEP from bottom up. The threshold electric field for the DEP placement of PbSe nanocrystals was roughly estimated to be about 8.3 x 104 V/cm under our experimental configuration. After the DEP process, several procedures for reducing contact resistances are attempted and measurements of intrinsic electron transport in versatile nanomaterials are performed. It is experimentally confirmed that electron transport in both PbSe nanocrystal arrays and polyaniline nanofibers agrees well with Prof. Ping Sheng's model of granular metallic conduction. In addition, electron transport in reduced-graphene-oxide flakes follows Mott's 2D variable-range-hopping model. This study illustrates an integration of the electron-beam lithography and the DEP techniques for a precise manipulation of nanomaterials into electronic circuits for characterization of intrinsic properties."
Electron hopping transport in 2D zinc oxide nanoflakes
(2017-06-01)
Jian, Dunliang
;
Lai, Jian-Jhong
;
Lin, Yen-Fu
;
Zhai, Jianpang
;
Li, Irene Ling
A sequential hydrothermal process was used to synthesize ZnO nanostructures on Si substrates. The synthesized ZnO nanostructures were inspected and presented a morphology of 2D structures, named nanoflakes. These ZnO nanoflakes had a thickness of tens of nanometers. An energy dispersive x-ray spectrum revealed their composition of only Zn and O elements. In addition, its crystalline structure was investigated by high-resolution transmission electron microscopy. The nanoflakes were then dispersed for another morphology measurement using atomic force microscopy and their average thickness was determined. The dispersed nanoflakes were further contacted with metal electrodes for electron transport measurements. Through the analysis of temperature-dependent resistivity, it was confirmed that the electron transport in such ZnO nanoflakes agrees well with the theory of Mott's 2D variable range hopping. The nature of the 2D electron system in the ZnO nanoflakes points to potential applications of this 2D semiconductor as a new channel material for electronics.
Electron transport in high-resistance semiconductor nanowires through two-probe measurements
(2010)
Lin, Yen-Fu
;
Chen, Tzu-Han
;
Chang, Chia-Hung
;
Chang, Yu-Wei
;
Chiu, Yi-Cheng
Since the successful fabrication of semiconductor nanowires, various techniques have been developed to contact these nanowires and to probe their intrinsic electrical properties. Although many novel quasi one-dimensional materials such as Pb(1-x)Mn(x)Se nanoarrays were recently produced, their intrinsic electron transport properties have not been extensively studied so far. In this work, we demonstrate that an ordinary source-drain configuration of field-effect transistors or the two-probe measurement can be applied to the exploration of the intrinsic properties of nanowires. This two-probe measurement approach also works on highly resistive nanowires without an Ohmic contact issue. By using this method, electron transport behavior, resistivity, and carrier concentrations of ZnO, InP, GaP, and Pb(1-x)Mn(x)Se semiconductor nanowires have been investigated. Due to the tiny cross-section and few conducting channels, a nanomaterial usually reveals an ultra high resistance. This technique demonstrates a two-probe characterization of nanostructures, paving the simplest way toward electrical characterizations of all high-resistance nanomaterials such as deoxyribonucleic acid (DNA), molecules and organics.
Electron transport in the two-dimensional channel material - zinc oxide nanoflake
(2018-03-01)
Lai, Jian-Jhong
;
Jian, Dunliang
;
Lin, Yen-Fu
;
Ku, Ming-Ming
;
Jian, Wen-Bin
ZnO nanoflakes of 3-5 mu m in lateral size and 15-20 nm in thickness are synthesized. The nanoflakes are used to make back-gated transistor devices. Electron transport in the ZnO nanoflake channel between source and drain electrodes are investigated. In the beginning, we argue and determine that electrons are in a two-dimensional system. We then apply Mott's two-dimensional variable range hopping model to analyze temperature and electric field dependences of resistivity. The disorder parameter, localization length, hopping distance, and hopping energy of the electron system in ZnO nanoflakes are obtained and, additionally, their temperature behaviors and dependences on room-temperature resistivity are presented. On the other hand, the basic transfer characteristics of the channel material are carried out, as well, and the carrier concentration, the mobility, and the Fermi wavelength of two-dimensional ZnO nanoflakes are estimated.
Electron Transport Properties of ZnO, InP, GaP, and Pb Se Nanowires By Two-Probe Measurements
(2010)
Lin, Yen-Fu
;
Jiye-Fang
;
Jian, Wen-Bin
;
電子物理學系
;
Department of Electrophysics
Nanowires (NWs) of four different materials, including ZnO, InP, GaP, and Pb1-xMnxSe, have been used for the fabrication of two-probe electronic devices to study electrical transport properties. The average diameters of ZnO, InP, GaP, and Pb1-xMnxSe NWs are about 40, 25, 25, 70 nm, respectively. Both electron-beam lithography and dielectrophoresis techniques are employed to either deposit two Ti/Au electrodes on single NW or positioned the NW into nanometer gap between two electrodes. Temperature dependent behaviors of resistance of two-probe devices are measured to explore the electron transport either in the NW or in the nanocontact formed in the interface between the NW and the Ti/Au electrodes. Two-probe devices with high and low room-temperature resistance are used to inspect and distinguish the interplay between the nanocontact and the NW. After the separation of NW-dominated devices from contact-dominated ones, the thermally activated transport in semiconductor ZnO, MP, and GaP NWs and the temperature independent tunneling conduction in Pb1-xMnxSe NWs have been revealed. On the other hand, the contact-dominated devices display electron hopping transport in the nanocontact. Moreover, the fluctuation-induced tunneling conduction in the overlapped Pb1-xMnxSe NWs has been observed.
Electron Transport Properties of ZnO, InP, GaP, and Pb(1-x)Mn(x)Se Nanowires By Two-Probe Measurements
(2010)
Lin, Yen-Fu
;
Jiye-Fang
;
Jian, Wen-Bin
;
電子物理學系
;
Department of Electrophysics
Nanowires (NWs) of four different materials, including ZnO, InP, GaP, and Pb(1-x)Mn(x)Se, have been used for the fabrication of two-probe electronic devices to study electrical transport properties. The average diameters of ZnO, InP, GaP, and Pb(1-x)Mn(x)Se NWs are about 40, 25, 25, 70 nm, respectively. Both electron-beam lithography and dielectrophoresis techniques are employed to either deposit two Ti/Au electrodes on single NW or positioned the NW into nanometer gap between two electrodes. Temperature dependent behaviors of resistance of two-probe devices are measured to explore the electron transport either in the NW or in the nanocontact formed in the interface between the NW and the Ti/Au electrodes. Two-probe devices with high and low room-temperature resistance are used to inspect and distinguish the interplay between the nanocontact and the NW. After the separation of NW-dominated devices from contact-dominated ones, the thermally activated transport in semiconductor ZnO, MP, and GaP NWs and the temperature independent tunneling conduction in Pb(1-x)Mn(x)Se NWs have been revealed. On the other hand, the contact-dominated devices display electron hopping transport in the nanocontact. Moreover, the fluctuation-induced tunneling conduction in the overlapped Pb(1-x)Mn(x)Se NWs has been observed.
High Mobilities in Layered InSe Transistors with Indium-Encapsulation-Induced Surface Charge Doping
(2018-11-02)
Li, Mengjiao
;
Lin, Che-Yi
;
Yang, Shih-Hsien
;
Chang, Yuan-Ming
;
Chang, Jen-Kuei
Tunability and stability in the electrical properties of 2D semiconductors pave the way for their practical applications in logic devices. A robust layered indium selenide (InSe) field-effect transistor (FET) with superior controlled stability is demonstrated by depositing an indium (In) doping layer. The optimized InSe FETs deliver an unprecedented high electron mobility up to 3700 cm(2) V-1 s(-1) at room temperature, which can be retained with 60% after 1 month. Further insight into the evolution of the position of the Fermi level and the microscopic device structure with different In thicknesses demonstrates an enhanced electron-doping behavior at the In/InSe interface. Furthermore, the contact resistance is also improved through the In insertion between InSe and Au electrodes, which coincides with the analysis of the low-frequency noise. The carrier fluctuation is attributed to the dominance of the phonon scattering events, which agrees with the observation of the temperature-dependent mobility. Finally, the flexible functionalities of the logic-circuit applications, for instance, inverter and not-and (NAND)/not-or (NOR) gates, are determined with these surface-doping InSe FETs, which establish a paradigm for 2D-based materials to overcome the bottleneck in the development of electronic devices.
Intrinsic Carrier Transport of Phase-Pure Homologous 2D Organolead Halide Hybrid Perovskite Single Crystals
(2018-12-27)
Li, Min-Ken
;
Chen, Tzu-Pei
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Lin, Yen-Fu
;
Raghavan, Chinnambedu Murugesan
;
Chen, Wei-Liang
This work reveals the intrinsic carrier transport behavior of 2D organolead halide perovskites based on phase-pure homologous (n = 1, 2, and 3) Ruddelsden-Popper perovskite (RPP) (BA)(2)(MA)(n-1)PbnI3n+1 single crystals. The 2D perovskite field effect transistors with high-quality exfoliated 2D perovskite bulk crystals are fabricated, and characteristic output and transfer curves are measured from individual single-crystal flakes with various n values under different temperatures. Unipolar n-type transport dominated the electrical properties of all these 2D RPP single crystals. The transport behavior of the 2D organolead halide hybrid perovskites exhibits a strong dependence on the n value and the mobility substantially increases as the ratio of the number of inorganic perovskite slabs per organic spacer increases. By extracting the effect of contact resistances, the corrected mobility values for n = 1, 2, and 3 are 2 x 10(-3), 8.3 x 10(-2), and 1.25 cm(2) V-1 s(-1) at 77 K, respectively. Furthermore, by combining temperature-dependent electrical transport and optical measurements, it is found that the origin of the carrier mobility dependence on the phase transition for 2D organolead halide perovskites is very different from that of their 3D counterparts. Our findings offer insight into fundamental carrier transport behavior of 2D organic-inorganic hybrid perovskites based on phase-pure homologous single crystals.
Low-Voltage Operational, Low-Power Consuming, and High Sensitive Tactile Switch Based on 2D Layered InSe Tribotronics
(2019-05-09)
Li, Mengjiao
;
Yang, Feng-Shou
;
Hsiao, Yung-Chi
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Lin, Che-Yi
;
Wu, Hsing-Mei
Electronics based on layered indium selenide (InSe) channels exhibit promising carrier mobility and switching characteristics. Here, an InSe tribotronic transistor (denoted as w/In InSe T-FET) obtained through the vertical combination of an In-doped InSe transistor and triboelectric nanogenerator is demonstrated. The w/In InSe T-FET can be operated by adjusting the distance between two triboelectrification layers, which generates a negative electrostatic potential that serves as a gate voltage to tune the charge carrier transport behavior of the InSe channel. Benefiting from the surface charging doping of the In layer, the w/In InSe T-FET exhibits high reliability and sensitivity with a large on/off current modulation of 10(6) under a low drain-source voltage of 0.1 V and external frictional force. To demonstrate its function as a power-saving tactile sensor, the w/In InSe T-FET is used to sense INSE in Morse code and power on a light-emitting diode. This work reveals the promise of 2D material-based tribotronics for use in nanosensors with low power consumption as well as in intelligent systems.
Multifunctional full-visible-spectrum optoelectronics based on a van der Waals heterostructure
(2019-12-01)
Yang, Shih-Hsien
;
Lee, Ko-Chun
;
Tsai, Meng-Yu
;
Chang, Yuan-Ming
;
Lin, Che-Yi
Multifunctional devices are expected to allow development of low-cost, highly integrated, and energy-efficient electronics for the internet of things (IoT) era. Here, we demonstrate an all-two-dimensional ReSe2/h-BN/graphene heterostructure (ReSe2 HS) consisting of a vertically coupled ReSe2 field-effect transistor and charge storage component, which possesses multifunctional characteristics for use in electronics and optoelectronics. As an electrically controlled non-volatile memory (NVM), the ReSe2 HS delivers high-performance multilevel data storage with a readout on/off current ratio exceeding 10(5) and excellent durability (> 10(4) s) at an ultralow V-ds of 50 mV, which benefits to the development of power saving devices. The ReSe2 HS design and high-photoresponsivity ReSe2 channel also achieve an energy efficient optical NVM with full-visible-spectrum distinction. Besides, the ReSe2 HS displays unique ambipolarity to operate as either an inverter or frequency doubler. We further propose a power-free ReSe2 HS optical memory matrix to simplify imaging systems. The ReSe2 HS shows promise for use in light-programmable information storage systems and neuromorphic computation with low power consumption.
Nano Approach Investigation of the Conduction Mechanism in Polyaniline Nanofibers
(2011-02-01)
Lin, Yen-Fu
;
Chen, Chien-Hsiang
;
Xie, Wen-Jia
;
Yang, Sheng-Hsiung
;
Hsu, Chain-Shu
A nanotechnological approach is applied to measurements of the electric field dependence of resistance under a high electric field while in low voltage. With this technique, the conduction mechanism on a mesoscopic scale is explored in a single, nonagglomerated nanofiber. Polyaniline nanofibers are prepared by vigorous mixing of aniline and oxidation agent ammonium persulfate in acid solution. They exhibit a uniform nanoscale morphology rather than agglomeration as that produced via conventional chemical oxidation. The as-synthesized polyaniline nanofibers are doped (dedoped) with a HCl acid (NH(3) base), and their temperature behaviors of resistances follow an exponential function with an exponent of T(-1/2). To measure the conduction mechanism in a single nanofiber, the dieiectrophoresis technique is implemented to position nanofibers on top of two electrodes with a nanogap of 100-600 nm, patterned by electron-beam lithography. After the devices are irradiated by electron beam to reduce contact resistances, their temperature behaviors and electric field dependences are unveiled. The experimental results agree well with the theoretical model of charging energy limited tunneling. Other theoretical models such as Efros-Shklovskii and Mott's one-dimensional hopping conduction are excluded after comparisons and arguments. Through fitting, the size of the conductive grain, separation distance between two grains, and charging energy per grain in a single polyaniline nanofiber are estimated to be about 4.9 nm, 2.8 nm, and 78 meV, respectively. The nanotechnological approach, where the nanogap and the dielectrophoresis technique are used for single nanofiber device fabrication, Is applied for determination of mesoscopic charge transport in a polyaniline conducting polymer.
Nanocontact disorder in InP nanowire devices for the enhancement of visible light and oxygen gas sensitivities
(2017-01-01)
Lin, Yen-Fu
;
Chang, Chia-Hung
;
Hung, Tsu-Chang
;
Liu, Zhaoping
;
Fang, Jiye
InP nanowires, synthesized through a self-seeded growth approach, are used in the fabrication of field-effect transistors which consist of source, drain, and back-gate electrodes. The weak gating voltage dependence implies low carrier concentrations whereas its behavior reveals native n-type doping in InP nanowires. These InP nanowire devices exhibit a vast variation of room-temperature resistance that raises a question about contact resistance. For devices of low room-temperature resistance, electron transport in InP nanowires is investigated using temperature dependent resistance in the temperature range between 80 and 300 K, and it can be analyzed using the model of thermal activation. For other devices of high room-temperature resistance, we take into account nanocontact resistance. Models of both Schottky contact and Mott's variable range hopping (VRH) are considered. The two resistances are connected in parallel to give total contact resistance of InP nanowire devices. After fitting experimental data by the proposed model, we estimate effective Schottky barriers and disorder contributions to nanocontact resistance. The effective Schottky barrier, and the nanocontact Schottky and Mott's VRH resistances are plotted as a function of the device room-temperature resistance which indicates the scale of disorder. Using room-temperature resistance of InP nanowire devices, the devices are classified into nanowire-or contact-dominated devices. The two different class of devices are used to check their photo-and gas-sensitivities. The contact-dominated InP nanowire devices show low dark current and low photocurrent as usual, but these contact-dominated devices give high ratio of photo-to dark-current. That result reveals a high photo-sensitivity for those devices of high nanocontact resistance. On the other hand, for gas sensing experiments, the contact-dominated devices show as well a high ratio of resistance under O-2 to that under N-2 gas exposure. (C) 2017 The Authors. Published by Elsevier B.V.
Nanocontact Disorder in Nanoelectronics for Modulation of Light and Gas Sensitivities
(2015-08-11)
Lin, Yen-Fu
;
Chang, Chia-Hung
;
Hung, Tsu-Chang
;
Jian, Wen-Bin
;
Tsukagoshi, Kazuhito
To fabricate reliable nanoelectronics, whether by top-down or bottom-up processes, it is necessary to study the electrical properties of nanocontacts. The effect of nanocontact disorder on device properties has been discussed but not quantitatively studied. Here, by carefully analyzing the temperature dependence of device electrical characteristics and by inspecting them with a microscope, we investigated the Schottky contact and Mott's variable-range-hopping resistances connected in parallel in the nanocontact. To interpret these parallel resistances, we proposed a model of Ti/TiOx in the interface between the metal electrodes and nanowires. The hopping resistance as well as the nanocontact disorder dominated the total device resistance for high-resistance devices, especially at low temperatures. Furthermore, we introduced nanocontact disorder to modulate the light and gas responsivities of the device; unexpectedly, it multiplied the sensitivities compared with the intrinsic sensitivity of the nanowires. Our results improve the collective understanding of electrical contacts to low-dimensional semiconductor devices and will aid performance optimization in future nanoelectronics.