CN101917161A - Carbon nanotube-based field effect transistor frequency multiplier - Google Patents
Carbon nanotube-based field effect transistor frequency multiplier Download PDFInfo
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- CN101917161A CN101917161A CN 201010219178 CN201010219178A CN101917161A CN 101917161 A CN101917161 A CN 101917161A CN 201010219178 CN201010219178 CN 201010219178 CN 201010219178 A CN201010219178 A CN 201010219178A CN 101917161 A CN101917161 A CN 101917161A
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Abstract
The invention discloses a carbon nanotube-based field effect transistor frequency multiplier. A field effect transistor adopting a small-forbidden band width carbon nanotube as a conducting channel serves as a core part of the frequency multiplier, and comprises a gate serving as an input end, a grounded source and a drain serving as an output end; and an AC signal input by the input end is offset to a maximum resistance point of the DC transfer characteristics of the field effect transistor and the output end supplies working power to the field effect transistor by using an offset DC source so as to realize frequency multiplication. The frequency multiplier of the invention has the characteristics of high conversion efficiency, quick frequency response, high signal gain, low cost, simple manufacture process and no need of complex post-processing circuits.
Description
Invention field
The invention belongs to the nano-electron technical field, relate to the field-effect transistor of carbon nano-tube, particularly based on the frequency multiplier of the field-effect transistor of carbon nano-tube.
Background technology
With the material with carbon element is the nanoelectronics of base, especially carbon nano-tube (Carbon Nanotube) is the nanoelectronics of base, be considered to have great application prospect, especially at radio frequency (RF) application (Rutherglen, C.et al.Nature Nanotechnology, 2009,4,811-819.).Since carbon nano-tube in 1991 is successfully prepared by people (Iijima, S.Nature, 1991,354,56-58.), the electronics of carbon back has been obtained huge progress.Electronics based on carbon nano-tube is little because of its size, speed is fast, low in energy consumption, technology is simple etc., and characteristics receive people's concern more and more widely.In general, carbon nano-tube can be divided into three classes based on its energy gap, the one, the carbon nano-tube of big energy gap (referring to realize the semi-conductor type single-walled carbon nano tube of the field effect transistor switch current ratio more than 100 times), the 2nd, there is not the carbon nano-tube (Single Walled Carbon Nanotube or the multi-walled carbon nano-tubes that comprise metal mold) of energy gap, the 3rd, the carbon nano-tube of little energy gap (can be Single Walled Carbon Nanotube or multi-walled carbon nano-tubes, can realize 1-100 times of field effect transistor switch current ratio) with semiconductor shell.The performance of the field-effect transistor of based semiconductor type carbon nano-tube has been pushed to ultimate attainment by people, and complementary metal-oxide-semiconductor (CMOS) inverter (Zhang, Z.Y.et al.ACS Nano, 2009 of ideal symmetrical have finally been obtained, 3,3781-3187.).And the carbon nano-tube of metal mold also is proved and is well suited for being used for realizing interconnected between the field-effect transistor, and have high high frequency response (Close, G.F.et al.Nano Letters, 2008,8,706-709.).And the carbon nano-tube of little energy gap never is widely used.
Frequency multiplier (Frequency Multiplier) is to make output signal frequency equal the circuit of frequency input signal integral multiple.Existing frequency multiplier has transistor frequency multiplier, varactor frequency multiplier, step recovery diode frequency multiplier etc.Existing frequency multiplier, its circuit complexity needs a lot of follow-up signal processing circuits, and as rectification circuit, filter circuit etc., and conversion efficiency is not very high, and it is also very expensive to be operated in its price of frequency multiplier of extremely high frequency (more than the 10GHz).
Summary of the invention
The objective of the invention is to expand the range of application of little energy gap carbon nano-tube, adopt and realize high performance frequency multiplier by simple framework based on the field-effect transistor of little energy gap carbon nano-tube.
The carbon nano-tube of little energy gap can provide good bipolarity characteristic, both can also can be by hole conduction by electron conduction.With little energy gap carbon nano-tube is that the typical structure of the field-effect transistor of conductive channel preparation comprises source end (being the source electrode) and the drain terminal (being drain electrode) that is positioned at the conductive channel two ends, and the grid (being gate electrode) between leak in the source, between described grid and the conductive channel insulating barrier, the transfer characteristic curve I of this field-effect transistor
Ds-V
Gs(drain terminal adopts the situation of voltage bias) and V
Ds-V
Gs(drain terminal adopts the situation of current offset) respectively as depicted in figs. 1 and 2, this field-effect transistor can show the bipolarity of good symmetry as can be seen, and such performance is well suited for being used for doing frequency multiplier.
With little energy gap carbon nano-tube is the core of the field-effect transistor of matrix manufacturing as device, can simply realize high performance frequency multiplier.Frequency multiplier of the present invention comprises a field-effect transistor, an input bias direct current source and an output bias direct current source, wherein: described field-effect transistor is a conductive channel with little energy gap carbon nano-tube, source end and drain terminal lay respectively at the two ends of conductive channel, between grid leaks in the source, grid and as being insulating barrier between the carbon nano-tube of conductive channel; Grid is the input of frequency multiplier, source end ground connection, and drain terminal is the output of frequency multiplier; The AC signal that input bias direct current source will be input to input is biased to the resistance maximum point of the direct current transfer characteristic of described field-effect transistor; And output bias direct current source connects output, provides a working power to field-effect transistor.
Input bias direct current source connects input signal source, the AC signal of input is transfused to the resistance maximum point (being the direct current minimum point, just transistorized work centre point) of holding the bias direct current source to be biased to the direct current transfer characteristic of described field-effect transistor and is input to input again.And under the driving in output bias direct current source, output just can collect output signal (for carbon nano-tube bipolarity frequency multiplier, the direct current biasing of output is the bigger the better, but also to consider device the electric current ability to bear and in it being limited in a suitable scope, otherwise can cause the permanent failure of device).
The operating circuit and the basic principle of the bipolarity frequency multiplier that the present invention realizes can be as shown in Figure 3.The core of circuit shown in Figure 3 is based on the field-effect transistor (FET) 1 of little energy gap carbon nano-tube; The grid of field-effect transistor 1 is the input of frequency multiplier, and input signal source connects dc offset voltage 4 (being input bias direct current source), fan-in again after input signal is biased; Source end ground connection; Drain terminal is the output of frequency multiplier, and output connects DC current source 3 (being output bias direct current source).Dc offset voltage 4 and DC current source 3 all are used for providing dc point to FET, and wherein dc offset voltage 4 is to be used for the V of bias input end
Gs, and DC current source 3 is the I that are used to provide output
Ds(annotate: DC current source 3 also can replace with a direct voltage source of having connected resistance, and is the V that is used to provide output for voltage bias
Ds).Basic principle shown in it is based on transfer characteristic (V shown in Figure 2
Ds-V
Gs).Input signal 2 is that a circular frequency is ω, and peak-to-peak value is V
Pp, inSinusoidal signal, output end signal is then setovered by current source 3, the size of current source 3 is I
DdTransfer characteristic (V by field-effect transistor 1
Ds-V
Gs), we can obtain the central point of its work, by dc offset voltage 4 field-effect transistor 1 are biased to the service area then, and output just can collect signal after the frequency multiplication by oscilloscope 5 then.The direct current biasing of output also can working voltage biasing, so just need receive on the voltage source again at the output resistance of connecting.
Specifically, input signal is when the A point, and input voltage is heart point at work, so the resistance of device is in its maximum, output signal also should be at voltage max A ' point so, and when input signal changed toward the B point, the voltage of output diminished gradually, thereby reach voltage minimum at B ', afterwards, input signal is got back to the C point, and output reaches voltage max C ' point once more equally, input signal arrives D point and E point more then, and corresponding output signal reaches and E ' point at D '.Like this, for the input signal of one-period, two cycles have but appearred in output signal, so just the very simple frequency multiplication that realized.And because near the sublinear of the transfer characteristic the FET work centre point makes that output signal does not need just can show good waveform through filtering.
By cascade frequency multiplier shown in Figure 3, just with the output signal of first order frequency multiplier input signal as second level frequency multiplier, the output that is about to the first order is received on the partial input, so just can obtain signal with respect to the quadruple of first order input signal at partial output.By that analogy, can further obtain octonary, the equifrequent signal of 16 frequencys multiplication, because very big based on the gain of the frequency multiplier of carbon nano-tube, this makes it can realize multistage cascade.
The field-effect transistor that the core of this device is is conductive channel with little energy gap carbon nano-tube, this transistor is because the energy gap of its conductive channel material is very little, so its on-off ratio also very little (can realize 1-100 times of on-off ratio).It also has good bipolar conductivity simultaneously, and just the conductivity in electronics and hole is all fine, and has reasonable symmetry.This device is typical nano field-effect transistor, and source and drain is used as the two ends of conduction, and grid is used as switch terminals, realizes regulation and control to the conductive capability of conductive channel by regulating grid voltage.Grid is not limited to bottom gate or top grid (independent gate), can also be other various structures that realize the grid regulation and control such as ring grid.Between grid and the conductive channel insulating barrier is arranged, realize regulation and control by the capacity effect of insulating barrier.And the structure of entire device also is not limited to self-alignment structure or non-self-alignment structure, can be used for realizing this frequency multiplier as long as can realize the structure of field effect.
The material of above-mentioned source end and drain terminal can be metal or other electric conducting materials, for example titanium, palladium, gold etc.; The material of grid can be metal or other electric conducting materials, for example titanium, palladium, tungsten nitride etc.; The material of insulating barrier can be oxide, nitride or nitrogen oxide, for example silica, hafnium oxide, aluminium oxide, yittrium oxide, silicon nitride etc.
Frequency multiplier of the present invention is when work, the grid of whole field-effect transistor exchanges input and is biased to the direct current minimum point, channel resistance maximum point just, central point during work that Here it is, the source is grounded then, and add the current source or the voltage source of a direct current at drain terminal, detects the AC signal of this point simultaneously with oscilloscope, the signal that can see the twice that a frequency is an incoming frequency can be observed, thus with regard to the very simple frequency multiplication that realized.
The frequency multiplier that the present invention is based on little energy gap carbon nanotube field-effect transistor is compared with traditional frequency multiplier, and its advantage is mainly reflected in:
1, this frequency multiplier constitutes simple, only need a field-effect transistor, and do not need the complicated part of rectification or filtering, because good bipolarity makes that the waveform of output is simply clean, most signal all concentrates on the frequency of two frequencys multiplication, and the process complexity that reduces has reduced cost;
2, frequency response height because the charge carrier in the carbon nano-tube can be subjected to the scattering on surface hardly in transport process, so its mobility is very high, thereby has very high cut-off frequency;
3, signal gain is big, can increase the ratio of its output signal and input signal by the size that improves current source, thus the gain that increases device, and this also helps the realization of cascade.
Description of drawings
Fig. 1 is based on the transfer characteristic (I of the field-effect transistor of little energy gap carbon nano-tube
Ds-V
Gs) curve, wherein, from 1V to 0.1V, every curve reduces 0.1V to Vds from top to bottom.
Fig. 2 is based on the transfer characteristic (V of the field-effect transistor of little energy gap carbon nano-tube
Ds-V
Gs) curve, wherein, I
DsFrom top to bottom from 15 μ A to 5 μ A, every curve reduces by 1 μ A.
Fig. 3 has shown the operation principle and the operating circuit of the frequency multiplier that the present invention is based on little energy gap carbon nanotube field-effect transistor.Wherein: the A ' in the output signal, B ', C ', D ', E ' respectively with input signal in the corresponding identical time point of A, B, C, D, E point; The 1st, the core of device---field-effect transistor (FET); The 2nd, the sinusoidal signal of input, peak-to-peak value is V
Pp, in, circular frequency is ω; The 3rd, the current source I of output
DdThe 4th, the direct voltage biasing V of input signal
G, DCThe 5th, the oscilloscope (OS) that acquired signal is used.
Fig. 4 is a kind of field-effect transistor of bottom grating structure, and wherein 11 is the conductive channel carbon nano-tube, and 12 and 13 are respectively source-drain electrode, the 14th, and the insulating barrier of grid, the 15th, silicon substrate.
Fig. 5 is a kind of field-effect transistor of top gate structure, and wherein 21 is the conductive channel carbon nano-tube, and 22 and 23 are respectively source-drain electrode, the 24th, and the insulating barrier of grid, the 25th, gate electrode, the 26th, dielectric base.
Fig. 6 has shown the frequency spectrograph test circuit based on frequency multiplier of the present invention, and wherein 1 is the core of device---field-effect transistor (FET); The 2nd, the sinusoidal signal of input, peak-to-peak value is V
Pp, in, circular frequency is ω; The 3rd, the current source I of output
DdThe 4th, the direct voltage biasing V of input signal
G, DCThe 6th, the isolator of direct current and AC signal (or the biasing device, Bias-T); The 7th, gather the frequency spectrograph (SA) that AC signal is used.
Fig. 7 is the spectrum curve that embodiment 2 measures.
Embodiment
Below in conjunction with accompanying drawing, further describe the present invention by embodiment, but do not limit the present invention in any way.
Bottom grating structure field-effect transistor as shown in Figure 4 is a conductive channel with the carbon nano-tube on the dielectric base 11; Two titanium electrodes on the carbon nano-tube 11 are respectively source electrode 12 and drain electrode 13; Substrate is the silicon chip that the surface heat oxidation processes is crossed, and the silica that the substrate surface thermal oxidation obtains is as gate medium 14 (being the insulating barrier between gate electrode 15 and the carbon nano-tube 11), and the heavily doped silicon substrate 15 of substrate is then as gate electrode.Concrete preparation process is as follows: be distributed in the shape that forms source, drain electrode on the carbon nano-tube of suprabasil little energy gap by photoetching, the titanium coating of evaporation one deck 50 nanometer thickness is as the source-drain electrode layer, then sample is put in the acetone and peeled off, remove unwanted metal level and promptly obtain source leakage metal electrode.
The prepared field-effect transistor that comes out measures its transfer characteristic curve by experiment, can know its working point, then in sinusoidal signal that has been biased to the 10kHz of working point of gate electrode 15 inputs, source electrode 12 ground connection, on drain electrode 13, connect the DC current source of one 10 μ A, simultaneously drain electrode 13 is also received on the oscilloscope, so just can be seen on oscilloscope that a frequency is the signal of the near sinusoidal of 20kHz, has just realized frequency multiplication.(concrete circuit diagram is with shown in Figure 3 identical)
The field-effect transistor of top gate structure as shown in Figure 5, little energy gap carbon nano-tube 21 is a conductive channel on the dielectric base 26 to be distributed in, two palladium electrodes on the carbon nano-tube 21 are respectively source electrode 22 and drain electrode 23, gate dielectric layer 24 is the hafnia films that obtained by ald, the Titanium that gate electrode 25 obtains for evaporation.Concrete preparation process is as follows:
1. on semiconductor carbon nanometer tube, form gate shapes, by grow hafnium oxide about one deck 15 nanometers of ald mode by photoetching;
At once the Titanium of method evaporation one deck 20 nanometer thickness by electron beam evaporation as gate electrode layer;
3. sample is put in the acetone and peeled off, prepare gate electrode;
4. photoetching forms the shape of source, drain electrode, and the palladium metal layer of evaporation one deck 50 nanometer thickness is put sample in the acetone into then and peeled off as the source-drain electrode layer, removes unwanted metal level and promptly obtains source leakage metal electrode.
Device is connected according to circuit shown in Figure 6, the sine wave signal 2 of the 1kHz that is setovered by direct voltage 4 one of the grid of field-effect transistor (FET) 1 input, wherein bias voltage 4 need obtain by the direct current transfer characteristic of measurement field effect transistor.Drain terminal connects the current source 3 of direct current by biasing device (Bias-T) 6 then, also is simultaneously by biasing device 6 AC signal to be coupled in the frequency spectrograph (SA) 7, thereby just can obtain the frequency spectrum of output signal.The frequency spectrum of output signal can see that signal power all concentrates on frequency multiplication 2kHz place more than 95%, can demonstrate the high efficiency of this frequency multiplier as shown in Figure 7.
Claims (6)
1. based on the application of field-effect transistor in frequency multiplier of little energy gap carbon nano-tube, wherein this field-effect transistor is a conductive channel with little energy gap carbon nano-tube, source end and drain terminal lay respectively at the two ends of conductive channel, between grid leaks in the source, grid and as being insulating barrier between the carbon nano-tube of conductive channel; Grid is as the input of frequency multiplier, source end ground connection, and drain terminal is as the output of frequency multiplier.
2. application as claimed in claim 1 is characterized in that, the field effect transistor switch current ratio of described field-effect transistor is 1-100.
3. frequency multiplier, comprise a field-effect transistor, an input bias direct current source and an output bias direct current source, wherein: described field-effect transistor is a conductive channel with little energy gap carbon nano-tube, source end and drain terminal lay respectively at the two ends of conductive channel, between grid leaks in the source, grid and as being insulating barrier between the carbon nano-tube of conductive channel; Grid is the input of frequency multiplier, source end ground connection, and drain terminal is the output of frequency multiplier; The AC signal that input bias direct current source will be input to input is biased to the resistance maximum point of the direct current transfer characteristic of described field-effect transistor; And output bias direct current source connects output, provides a working power to field-effect transistor.
4. frequency multiplier as claimed in claim 3 is characterized in that, the field effect transistor switch current ratio of described field-effect transistor is 1-100.
5. frequency multiplier as claimed in claim 3 is characterized in that, described input bias direct current source is a direct voltage source that connects input signal source.
6. frequency multiplier as claimed in claim 3 is characterized in that, described output bias direct current source is a DC current source, or the direct voltage source of the resistance of having connected.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108461446A (en) * | 2018-03-26 | 2018-08-28 | 北京大学 | A kind of preparation method of list grid graphene frequency multiplier |
| WO2018215892A1 (en) * | 2017-05-23 | 2018-11-29 | International Business Machines Corporation | Semiconductor device |
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2010
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Non-Patent Citations (3)
| Title |
|---|
| 《Applied Physics Letters》 20100427 Zhenxing Wang等 A high-performance top-gate graphene field-effect transistor based frequency doubler 第96卷, 第17期 * |
| 《Applied Physics Letters》 20100427 Zhenxing Wang等 A high-performance top-gate graphene field-effect transistor based frequency doubler 第96卷, 第17期 2 * |
| 《NANO LETTERS》 20050603 Fei Liu等 Determination of the small band gap of carbon nanotubes using the ambipolar random telegraph signal 第5卷, 第7期 * |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018215892A1 (en) * | 2017-05-23 | 2018-11-29 | International Business Machines Corporation | Semiconductor device |
| GB2577208A (en) * | 2017-05-23 | 2020-03-18 | Ibm | Semiconductor device |
| CN108461446A (en) * | 2018-03-26 | 2018-08-28 | 北京大学 | A kind of preparation method of list grid graphene frequency multiplier |
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Application publication date: 20101215 |