AlN/GaN resonant tunneling diodes(RTDs)were grown separately on freestanding Ga N(FS-GaN)substrates and sapphire substrates by plasma-assisted molecular-beam epitaxy(PA-MBE).Room temperature negative differential resi...AlN/GaN resonant tunneling diodes(RTDs)were grown separately on freestanding Ga N(FS-GaN)substrates and sapphire substrates by plasma-assisted molecular-beam epitaxy(PA-MBE).Room temperature negative differential resistance(NDR)was obtained under forward bias for the RTDs grown on FS-GaN substrates,with the peak current densities(Jp)of 175-700 kA/cm^(2)and peak-to-valley current ratios(PVCRs)of 1.01-1.21.Two resonant peaks were also observed for some RTDs at room temperature.The effects of two types of substrates on epitaxy quality and device performance of GaN-based RTDs were firstly investigated systematically,showing that lower dislocation densities,flatter surface morphology,and steeper heterogeneous interfaces were the key factors to achieving NDR for RTDs.展开更多
In this work,the electronic properties of resonant tunneling diodes(RTDs) based on GaN-AlxGa(1-x)N double barriers are investigated by using the non-equilibrium Green functions formalism(NEG).These materials eac...In this work,the electronic properties of resonant tunneling diodes(RTDs) based on GaN-AlxGa(1-x)N double barriers are investigated by using the non-equilibrium Green functions formalism(NEG).These materials each present a wide conduction band discontinuity and a strong internal piezoelectric field,which greatly affect the electronic transport properties.The electronic density,the transmission coefficient,and the current–voltage characteristics are computed with considering the spontaneous and piezoelectric polarizations.The influence of the quantum size on the transmission coefficient is analyzed by varying GaN quantum well thickness,AlxGa1-xN width,and the aluminum concentration xAl.The results show that the transmission coefficient more strongly depends on the thickness of the quantum well than the barrier;it exhibits a series of resonant peaks and valleys as the quantum well width increases.In addition,it is found that the negative differential resistance(NDR) in the current–voltage(I–V) characteristic strongly depends on aluminum concentration xAl.It is shown that the peak-to-valley ratio(PVR) increases with xAlvalue decreasing.These findings open the door for developing vertical transport nitrides-based ISB devices such as THz lasers and detectors.展开更多
The characteristics of N-type accumulation-mode MOS (NMOS) varactors line periodically loaded with resonant tunneling diodes (RTDs) are used for soliton-like pulses generation and shaping. The problem of wide pulse br...The characteristics of N-type accumulation-mode MOS (NMOS) varactors line periodically loaded with resonant tunneling diodes (RTDs) are used for soliton-like pulses generation and shaping. The problem of wide pulse breaking up into multiple pulses rather than a single is solved. Applying perturbative analysis, we show that the dynamics of the nonlinear transmission line (NLTL) is reduced to expanded Korteweg-de Vries (KdV) equation. Moreover, numerical integration of nonlinear differential and difference equations that result from the mathematical analysis of the line is discussed. As results, NLTL can simultaneously sharpen both leading and trailing of pulse edges and one could obtain a rising and sharpening step pulse.展开更多
This article reports on the development of a simple two-step lithography process for double barrier quantum well(DBQW)InGaAs/AlAs resonant tunneling diode(RTD)on a semi-insulating indium phosphide(InP)substrate using ...This article reports on the development of a simple two-step lithography process for double barrier quantum well(DBQW)InGaAs/AlAs resonant tunneling diode(RTD)on a semi-insulating indium phosphide(InP)substrate using an air-bridge technology.This approach minimizes processing steps,and therefore the processing time as well as the required resources.It is particularly suited for material qualification of new epitaxial layer designs.A DC performance comparison between the proposed process and the conventional process shows approximately the same results.We expect that this novel technique will aid in the recent and continuing rapid advances in RTD technology.展开更多
Resonant tunnelling diodes (RTDs) have negative differential resistance effect, and the current-voltage characteristics change as a function of external stress, which is regarded as mesc-piezoresistance effect of RT...Resonant tunnelling diodes (RTDs) have negative differential resistance effect, and the current-voltage characteristics change as a function of external stress, which is regarded as mesc-piezoresistance effect of RTDs. In this paper, a novel micro-accelerometer based on AlAs/GaAs/In0.1Ga0.9As/GaAs/AlAs RTDs is designed and fabricated to be a four-beam-mass structure, and an RTD-Wheatstone bridge measurement system is established to test the basic properties of this novel accelerometer. According to the experimental results, the sensitivity of the RTD based micro-accelerometer is adjustable within a range of 3 orders when the bias voltage of the sensor changes. The largest sensitivity of this RTD based miero-accelerometer is 560.2025 mV/g which is about 10 times larger than that of silicon based micro piezoresistive accelerometer, while the smallest one is 1.49135 mV/g.展开更多
This paper investigates the dependence of current voltage characteristics of AlAs/In0.53Ga0.47As/InAs resonant tunnelling diodes (RTDs) on spacer layer thickness. It finds that the peak and the valley current densit...This paper investigates the dependence of current voltage characteristics of AlAs/In0.53Ga0.47As/InAs resonant tunnelling diodes (RTDs) on spacer layer thickness. It finds that the peak and the valley current density J in the negative differential resistance (NDR) region depends strongly on the thickness of the spacer layer. The measured peak to valley current ratio of RTDs studied here is shown to improve while the current density through RTDs decreases with increasing spacer layer thickness below a critical value.展开更多
This paper reports that InAs/In0.53Ga0.47As/AlAs resonant tunnelling diodes have been grown on InP substrates by molecular beam epitaxy. Peak to valley current ratio of these devices is 17 at 300K. A peak current dens...This paper reports that InAs/In0.53Ga0.47As/AlAs resonant tunnelling diodes have been grown on InP substrates by molecular beam epitaxy. Peak to valley current ratio of these devices is 17 at 300K. A peak current density of 3kA/cm^2 has been obtained for diodes with AlAs barriers of ten monolayers, and an Ino.53Ga0.47As well of eight monolayers with four monolayers of InAs insert layer. The effects of growth interruption for smoothing potential barrier interfaces have been investigated by high resolution transmission electron microscope.展开更多
The spin transport property of a ferromagnet (FM)/insulator (Ⅰ)/resonant tunneling diode (RTD) heterostructure was studied. The transmission coefficient and spin polarization in a multilayered heterostructure w...The spin transport property of a ferromagnet (FM)/insulator (Ⅰ)/resonant tunneling diode (RTD) heterostructure was studied. The transmission coefficient and spin polarization in a multilayered heterostructure was calculated by a Schrdinger wave equation. An Airy function formalism approach was used to solve this equation. Based on the transfer matrix approach,the transmittivity of the structure was determined as a function of the Feimi energy and other parameters. The result shows that the spin polarization induced by the structure oscillates with the increasing Fermi energy of the FM layer. While the thickness of the RTD is reduced,the resonant peaks become broad. In the heterostructure,the spin polarization reaches as high as 40% and can be easily controlled by the external bias voltage.展开更多
This paper studies the dependence of I - V characteristics on quantum well widths in AIAs/In0.53Ga0.47As and AIAs/In0.53Ga0.47As/InAs resonant tunnelling structures grown on InP substrates. It shows that the peak and ...This paper studies the dependence of I - V characteristics on quantum well widths in AIAs/In0.53Ga0.47As and AIAs/In0.53Ga0.47As/InAs resonant tunnelling structures grown on InP substrates. It shows that the peak and the valley current density in the negative differential resistance region are closely related with quantum well width. The measured peak current density, valley current densities and peak-to-valley current ratio of resonant tunnelling diodes are continually decreasing with increasing well width.展开更多
This paper reports that the structures of AlGaAs/InGaAs high electron mobility transistor (HEMT) and AlAs/GaAs resonant tunnelling diode (RTD) are epitaxially grown by molecular beam epitaxy (MBE) in turn on a G...This paper reports that the structures of AlGaAs/InGaAs high electron mobility transistor (HEMT) and AlAs/GaAs resonant tunnelling diode (RTD) are epitaxially grown by molecular beam epitaxy (MBE) in turn on a GaAs substrate. An Alo.24Gao.76As chair barrier layer, which is grown adjacent to the top AlAs barrier, helps to reduce the valley current of RTD. The peak-to-valley current ratio of fabricated RTD is 4.8 and the transconductance for the 1-μm gate HEMT is 125mS/mm. A static inverter which consists of two RTDs and a HEMT is designed and fabricated. Unlike a conventional CMOS inverter, the novel inverter exhibits self-latching property.展开更多
The problems existing in the binary logic system and the advantages of multiple-valued logic (MVL) are introduced. A literal circuit with three-track-output structure is created based on resonant tunneling diodes (RTD...The problems existing in the binary logic system and the advantages of multiple-valued logic (MVL) are introduced. A literal circuit with three-track-output structure is created based on resonant tunneling diodes (RTDs) and it has the most basic memory function. A ternary RTD D flip-flop with pre-set and pre-reset functions is also designed, the key module of which is the RTD literal circuit. Two types of output structure of the ternary RTD D flip-flop are optional: one is three-track and the other is single-track; these two structures can be transformed conveniently by merely adding tri-valued RTD NAND, NOR, and inverter units after the three-track output. The design is verified by simulation. Ternary flip-flop consists of an RTD literal circuit and it not only is easy to understand and implement but also provides a solution for the algebraic interface between the multiple-valued logic and the binary logic. The method can also be used for design of other types of multiple-valued RTD flip-flop circuits.展开更多
Resonant tunneling diodes(RTD)have the potential for compact and coherent terahertz(THz)sources operating at room temperature,but their low output power severely restricts their application in THz frequency range....Resonant tunneling diodes(RTD)have the potential for compact and coherent terahertz(THz)sources operating at room temperature,but their low output power severely restricts their application in THz frequency range.In this paper,two methods are adopted to increase the peak current of RTD for enhancing its output power.First,different metal contact systems(including Pt/Ti/Pt/Au and Au Ge/Ni/Au)for RTD contact are introduced,and a higher current of RTD with Pt/Ti/Pt/Au contact demonstrates the superior contact characteristic of Pt/Ti/Pt/Au contact system.Second,the double barrier structure(DBS)of RTD is well designed to further improve the characteristic of RTD,and a high peak current of 154 kA/cm^2 is achieved at room temperature.The improved peak current is very beneficial for increasing the output power of RTD oscillator.展开更多
An In0.53Ga0.47As/AlAs resonant tunneling diode (RTD) with a high doping emitter is designed and fabricated using air bridge technology. The RTD exhibits a high peak-to-valley current ratio (PVCR) of more than 40 ...An In0.53Ga0.47As/AlAs resonant tunneling diode (RTD) with a high doping emitter is designed and fabricated using air bridge technology. The RTD exhibits a high peak-to-valley current ratio (PVCR) of more than 40 at room temperature, with a peak current density of 24 kA/cm2. The extraction of device parameters from DC and microwave measurements is presented together with an RTD equivalent circuit. The high PVCR RTD with small intrinsic capacitance is favorable for microwave/THz applications.展开更多
A MOS-NDR(negative differential resistance) transistor which is composed of four n-channel metaloxide -semiconductor field effect transistors(nMOSFETs) is fabricated in standard 0.35μm CMOS technology.This device...A MOS-NDR(negative differential resistance) transistor which is composed of four n-channel metaloxide -semiconductor field effect transistors(nMOSFETs) is fabricated in standard 0.35μm CMOS technology.This device exhibits NDR similar to conventional NDR devices such as the compound material based RTD(resonant tunneling diode) in current-voltage characteristics.At the same time it can realize a modulation effect by the third terminal. Based on the MOS-NDR transistor,a flexible logic circuit is realized in this work,which can transfer from the NAND gate to the NOR gate by suitably changing the threshold voltage of the MOS-NDR transistor.It turns out that MOS-NDR based circuits have the advantages of improved circuit compaction and reduced process complexity due to using the standard IC design and fabrication procedure.展开更多
基金Project supported by the National Key R&D Program of China(Grant No.2018YFB0406600)the National Natural Science Foundation of China(Grant Nos.61875224,61804163,and 61827823)+2 种基金Key Laboratory of Microelectronic Devices and Integration Technology,Chinese Academy of Sciences(Grant No.Y9TAQ21)Key Laboratory of Nano-devices and Applications,Chinese Academy of Sciences(Grant No.Y8AAQ21001)Guangxi Key Laboratory of Precision Navigation Technology and Application,Guilin University of Electronic Technology(Grant No.DH202011)。
文摘AlN/GaN resonant tunneling diodes(RTDs)were grown separately on freestanding Ga N(FS-GaN)substrates and sapphire substrates by plasma-assisted molecular-beam epitaxy(PA-MBE).Room temperature negative differential resistance(NDR)was obtained under forward bias for the RTDs grown on FS-GaN substrates,with the peak current densities(Jp)of 175-700 kA/cm^(2)and peak-to-valley current ratios(PVCRs)of 1.01-1.21.Two resonant peaks were also observed for some RTDs at room temperature.The effects of two types of substrates on epitaxy quality and device performance of GaN-based RTDs were firstly investigated systematically,showing that lower dislocation densities,flatter surface morphology,and steeper heterogeneous interfaces were the key factors to achieving NDR for RTDs.
基金Project supported by the Deanship of Scientific Research of University of Dammam(Grant No.2014137)
文摘In this work,the electronic properties of resonant tunneling diodes(RTDs) based on GaN-AlxGa(1-x)N double barriers are investigated by using the non-equilibrium Green functions formalism(NEG).These materials each present a wide conduction band discontinuity and a strong internal piezoelectric field,which greatly affect the electronic transport properties.The electronic density,the transmission coefficient,and the current–voltage characteristics are computed with considering the spontaneous and piezoelectric polarizations.The influence of the quantum size on the transmission coefficient is analyzed by varying GaN quantum well thickness,AlxGa1-xN width,and the aluminum concentration xAl.The results show that the transmission coefficient more strongly depends on the thickness of the quantum well than the barrier;it exhibits a series of resonant peaks and valleys as the quantum well width increases.In addition,it is found that the negative differential resistance(NDR) in the current–voltage(I–V) characteristic strongly depends on aluminum concentration xAl.It is shown that the peak-to-valley ratio(PVR) increases with xAlvalue decreasing.These findings open the door for developing vertical transport nitrides-based ISB devices such as THz lasers and detectors.
文摘The characteristics of N-type accumulation-mode MOS (NMOS) varactors line periodically loaded with resonant tunneling diodes (RTDs) are used for soliton-like pulses generation and shaping. The problem of wide pulse breaking up into multiple pulses rather than a single is solved. Applying perturbative analysis, we show that the dynamics of the nonlinear transmission line (NLTL) is reduced to expanded Korteweg-de Vries (KdV) equation. Moreover, numerical integration of nonlinear differential and difference equations that result from the mathematical analysis of the line is discussed. As results, NLTL can simultaneously sharpen both leading and trailing of pulse edges and one could obtain a rising and sharpening step pulse.
基金funded by Horizon 2020 Future and Emerging Technologies ChipAI project under the grant agreement 828841.
文摘This article reports on the development of a simple two-step lithography process for double barrier quantum well(DBQW)InGaAs/AlAs resonant tunneling diode(RTD)on a semi-insulating indium phosphide(InP)substrate using an air-bridge technology.This approach minimizes processing steps,and therefore the processing time as well as the required resources.It is particularly suited for material qualification of new epitaxial layer designs.A DC performance comparison between the proposed process and the conventional process shows approximately the same results.We expect that this novel technique will aid in the recent and continuing rapid advances in RTD technology.
基金supported in part by the National Natural Science Foundation of China (Grant No 50775209)the Fork Ying Tung Education Foundation (Grant No 101052)Program for Excellent Talents by Ministry of Education of China
文摘Resonant tunnelling diodes (RTDs) have negative differential resistance effect, and the current-voltage characteristics change as a function of external stress, which is regarded as mesc-piezoresistance effect of RTDs. In this paper, a novel micro-accelerometer based on AlAs/GaAs/In0.1Ga0.9As/GaAs/AlAs RTDs is designed and fabricated to be a four-beam-mass structure, and an RTD-Wheatstone bridge measurement system is established to test the basic properties of this novel accelerometer. According to the experimental results, the sensitivity of the RTD based micro-accelerometer is adjustable within a range of 3 orders when the bias voltage of the sensor changes. The largest sensitivity of this RTD based miero-accelerometer is 560.2025 mV/g which is about 10 times larger than that of silicon based micro piezoresistive accelerometer, while the smallest one is 1.49135 mV/g.
文摘This paper investigates the dependence of current voltage characteristics of AlAs/In0.53Ga0.47As/InAs resonant tunnelling diodes (RTDs) on spacer layer thickness. It finds that the peak and the valley current density J in the negative differential resistance (NDR) region depends strongly on the thickness of the spacer layer. The measured peak to valley current ratio of RTDs studied here is shown to improve while the current density through RTDs decreases with increasing spacer layer thickness below a critical value.
文摘This paper reports that InAs/In0.53Ga0.47As/AlAs resonant tunnelling diodes have been grown on InP substrates by molecular beam epitaxy. Peak to valley current ratio of these devices is 17 at 300K. A peak current density of 3kA/cm^2 has been obtained for diodes with AlAs barriers of ten monolayers, and an Ino.53Ga0.47As well of eight monolayers with four monolayers of InAs insert layer. The effects of growth interruption for smoothing potential barrier interfaces have been investigated by high resolution transmission electron microscope.
基金the National Natural Science Foundation of China and Beijing (No50831002,No50701005)the Specialized Research Fund for the Doctoral Program of Higher Education of China (No20070008024)+1 种基金the National Basic Research and Development Program of China (No2007CB936202)the Foundation of the Ministry of Education of China for Returned Scholars
文摘The spin transport property of a ferromagnet (FM)/insulator (Ⅰ)/resonant tunneling diode (RTD) heterostructure was studied. The transmission coefficient and spin polarization in a multilayered heterostructure was calculated by a Schrdinger wave equation. An Airy function formalism approach was used to solve this equation. Based on the transfer matrix approach,the transmittivity of the structure was determined as a function of the Feimi energy and other parameters. The result shows that the spin polarization induced by the structure oscillates with the increasing Fermi energy of the FM layer. While the thickness of the RTD is reduced,the resonant peaks become broad. In the heterostructure,the spin polarization reaches as high as 40% and can be easily controlled by the external bias voltage.
文摘This paper studies the dependence of I - V characteristics on quantum well widths in AIAs/In0.53Ga0.47As and AIAs/In0.53Ga0.47As/InAs resonant tunnelling structures grown on InP substrates. It shows that the peak and the valley current density in the negative differential resistance region are closely related with quantum well width. The measured peak current density, valley current densities and peak-to-valley current ratio of resonant tunnelling diodes are continually decreasing with increasing well width.
文摘This paper reports that the structures of AlGaAs/InGaAs high electron mobility transistor (HEMT) and AlAs/GaAs resonant tunnelling diode (RTD) are epitaxially grown by molecular beam epitaxy (MBE) in turn on a GaAs substrate. An Alo.24Gao.76As chair barrier layer, which is grown adjacent to the top AlAs barrier, helps to reduce the valley current of RTD. The peak-to-valley current ratio of fabricated RTD is 4.8 and the transconductance for the 1-μm gate HEMT is 125mS/mm. A static inverter which consists of two RTDs and a HEMT is designed and fabricated. Unlike a conventional CMOS inverter, the novel inverter exhibits self-latching property.
文摘The problems existing in the binary logic system and the advantages of multiple-valued logic (MVL) are introduced. A literal circuit with three-track-output structure is created based on resonant tunneling diodes (RTDs) and it has the most basic memory function. A ternary RTD D flip-flop with pre-set and pre-reset functions is also designed, the key module of which is the RTD literal circuit. Two types of output structure of the ternary RTD D flip-flop are optional: one is three-track and the other is single-track; these two structures can be transformed conveniently by merely adding tri-valued RTD NAND, NOR, and inverter units after the three-track output. The design is verified by simulation. Ternary flip-flop consists of an RTD literal circuit and it not only is easy to understand and implement but also provides a solution for the algebraic interface between the multiple-valued logic and the binary logic. The method can also be used for design of other types of multiple-valued RTD flip-flop circuits.
文摘Resonant tunneling diodes(RTD)have the potential for compact and coherent terahertz(THz)sources operating at room temperature,but their low output power severely restricts their application in THz frequency range.In this paper,two methods are adopted to increase the peak current of RTD for enhancing its output power.First,different metal contact systems(including Pt/Ti/Pt/Au and Au Ge/Ni/Au)for RTD contact are introduced,and a higher current of RTD with Pt/Ti/Pt/Au contact demonstrates the superior contact characteristic of Pt/Ti/Pt/Au contact system.Second,the double barrier structure(DBS)of RTD is well designed to further improve the characteristic of RTD,and a high peak current of 154 kA/cm^2 is achieved at room temperature.The improved peak current is very beneficial for increasing the output power of RTD oscillator.
基金Project supported by the National Fundamental Research Program of China(No.2009CB320207)
文摘An In0.53Ga0.47As/AlAs resonant tunneling diode (RTD) with a high doping emitter is designed and fabricated using air bridge technology. The RTD exhibits a high peak-to-valley current ratio (PVCR) of more than 40 at room temperature, with a peak current density of 24 kA/cm2. The extraction of device parameters from DC and microwave measurements is presented together with an RTD equivalent circuit. The high PVCR RTD with small intrinsic capacitance is favorable for microwave/THz applications.
基金supported by the National Natural Science Foundation of China(Nos.60536030,60502005)the National High Technology Research and Development Program of China(Nos.2007AA01Z2A5,2006AA01Z239,2007AA03Z454).
文摘A MOS-NDR(negative differential resistance) transistor which is composed of four n-channel metaloxide -semiconductor field effect transistors(nMOSFETs) is fabricated in standard 0.35μm CMOS technology.This device exhibits NDR similar to conventional NDR devices such as the compound material based RTD(resonant tunneling diode) in current-voltage characteristics.At the same time it can realize a modulation effect by the third terminal. Based on the MOS-NDR transistor,a flexible logic circuit is realized in this work,which can transfer from the NAND gate to the NOR gate by suitably changing the threshold voltage of the MOS-NDR transistor.It turns out that MOS-NDR based circuits have the advantages of improved circuit compaction and reduced process complexity due to using the standard IC design and fabrication procedure.