CN103367518A - Surface plasmon coupling terahertz quantum well detector - Google Patents

Abstract

The invention provides a surface plasmon coupling terahertz quantum well detector, which comprises a semiconductor substrate, a lower electrode, a multi-quantum well structure, an upper electrode and a metal grating, wherein the metal grating is used for realizing polarity deflection of incident photons. The incident photons can be enabled to be interacted with electrons in the upper electrode through adjusting the period of the metal grating, the width of a metal strip, and the electron doping density and the thickness of the upper electrode so as to from surface plasmons on the surface of the upper electrode. The device is located in a sub-wavelength range at a terahertz frequency band because the thickness is only 2-5mum. Therefore, evanescent waves corresponding to the surface plasmons can improve the sub-band absorption efficiency of the device at the resonant frequency, and improves the response rate and the working temperature of the device.

Description

A kind of surface phasmon coupling Terahertz quantum well detector

Technical field

The invention belongs to semiconductor applications, particularly relate to a kind of surface phasmon coupling Terahertz quantum well detector.

Background technology

Quantum well detector is a kind of important detector that is operated in mid and far infrared, Terahertz frequency range.The Terahertz quantum well detector is the photon type detector that the Terahertz frequency range has the important application prospect, has the characteristics such as the fast and narrowband response of highly sensitive, speed of detection.The primary structure of this detector comprises contact layer, multiple quantum well layer and lower contact layer.The quantum well number is between 10～100, and on the quantum trap growth direction, the thickness of device is between 2.0～5.0 μ m.Introduce bound electron in the quantum well by being entrained in, because parabola shaped energy dispersion relation, these bound electrons only can be absorbed in the photon that electric field component is arranged on the quantum trap growth direction, realization from the bound state to the continuous state or the transition of quasicontinuum state, the polarity selection rule of Here it is Terahertz quantum well detector.Applying up and down bias voltage (concrete numerical value looks quantum well quantity and operation wavelength is determined) between the contact layer during device work, if the light incident that meets quantum well detector polarity selection rule is arranged, bound electron transits to continuous state or quasicontinuum state, under the applying bias effect, form photoelectric current, realize the conversion of electro-optical signal.Light (the incident light direction is consistent with the quantum trap growth direction) for normal incidence can not cause the transition of bound electron, can't form photoelectric current.Therefore, usually to change the coupling process that incident direction of light or selection can change the incident light polarised direction.

Because the Terahertz quantum well detector is based on the unipolar device of intersubband transitions, need to adopt special optical coupling mode to obtain to meet the incident light of sub-band transition selection rule.For Terahertz quantum well detector unit component, the mode of miter angle incident can realize optical coupling, specific practice is at the substrate of device side together with the carrying device, grind out the minute surface that becomes miter angle with the device growth direction, make vertical this minute surface incident of incident light, to obtain the electric field component on the quantum trap growth direction.Yet concerning miter angle incident light coupled modes, the light that only accounts for total projectile energy 25% might be utilized.

Therefore, provide a kind of high subband absorption efficiency, the Terahertz quantum well detector of high responsiveness and elevated operating temperature is real to belong to necessary.

Summary of the invention

The shortcoming of prior art in view of the above the object of the present invention is to provide a kind of surface phasmon coupling Terahertz quantum well detector, is used for solving prior art subband absorption efficiency, and responsiveness and working temperature be lower problem all.

Reach for achieving the above object other relevant purposes, the invention provides a kind of surface phasmon coupling Terahertz quantum well detector, be used for the detection of incident photon, comprise at least: Semiconductor substrate; Bottom electrode is incorporated into described Semiconductor substrate; Multi-quantum pit structure is incorporated into described bottom electrode, comprises a plurality of stacked GaAs/ (Al, Ga) As quantum well; Top electrode is incorporated into described multi-quantum pit structure, and the described very electron adulterated concentration that powers on is 1.0 * 10 ¹⁷～5.0 * 10 ¹⁷/ cm ³The n-GaAs layer that mixes of N-shaped, its thickness is 0.2～0.6 μ m; Metal grating, be incorporated into described top electrode, comprise a plurality of spaced bonding jumpers, the cycle of described metal grating is 10～30 μ m, the width of described bonding jumper is 5～15 μ m, be used for to realize the polarity deflection of incident photon, and make electron interaction in described incident photon and the described top electrode with at described upper electrode surface formation surface phasmon.

As a preferred version of surface phasmon coupling Terahertz quantum well detector of the present invention, the described very electron adulterated concentration that powers on is 3.0 * 10 ¹⁷～5.0 * 10 ¹⁷/ cm ³

As a preferred version of surface phasmon coupling Terahertz quantum well detector of the present invention, the cycle of described metal grating is 15～25 μ m, and the width of described bonding jumper is 8 ~ 12 μ m.

As a preferred version of surface phasmon coupling Terahertz quantum well detector of the present invention, described bottom electrode is the n-GaAs layer that N-shaped mixes, and its electron adulterated concentration is 1.0 * 10 ¹⁷～5.0 * 10 ¹⁷/ cm ³

In surface phasmon coupling Terahertz quantum well detector of the present invention, the mol ratio of Al is 1%～5% in described GaAs/ (Al, Ga) the As quantum well.

In surface phasmon coupling Terahertz quantum well detector of the present invention, the quantity of GaAs/ (Al, Ga) the As quantum well in the described multi-quantum pit structure is 20～40.

In surface phasmon coupling Terahertz quantum well detector of the present invention, the width of described GaAs/ (Al, Ga) As quantum well is 10～20nm.

In surface phasmon coupling Terahertz quantum well detector of the present invention, the material of described metal grating is the alloy of Al, Cu, Au, Pt or its combination in any.

In surface phasmon coupling Terahertz quantum well detector of the present invention, the thickness of described metal grating is 0.2～0.8 μ m.

As mentioned above, surface phasmon coupling Terahertz quantum well detector of the present invention has following beneficial effect: the present invention includes: Semiconductor substrate, bottom electrode, multi-quantum pit structure, top electrode and metal grating.Described metal grating is used for realizing the polarity deflection of incident photon, adjust the cycle of described metal grating, the width of bonding jumper and the electron adulterated concentration of top electrode, the thickness of top electrode, can make electron interaction in incident photon and the described top electrode to form surface phasmon in described upper electrode surface.Because thickness of detector only is 2～5 μ m, be in the sub-wavelength scope in the Terahertz frequency range, thereby the evanescent wave that surface phasmon is corresponding can improve device subband absorption efficiency at the resonance frequency place, and improve response device rate and working temperature.

Description of drawings

Fig. 1 a is shown as the cross section structure schematic diagram of surface phasmon coupling Terahertz quantum well detector of the present invention.

Fig. 1 b is shown as the planar structure schematic diagram of surface phasmon coupling Terahertz quantum well detector of the present invention.

Fig. 2 is shown as the surface phasmon in the surface phasmon coupling Terahertz quantum well detector n-GaAs layer that Air-N-shaped mixes of the present invention-quantum well three-decker | Ez| field distribution and surface phasmon ω-β dispersion relation figure.

Fig. 3 is shown as surface phasmon coupling Terahertz quantum well detector of the present invention | E _z| ²With miter angle coupling | E _z| ²Comparison diagram.

The element numbers explanation

11 Semiconductor substrate

12 bottom electrodes

13 multi-quantum pit structures

131 GaAs layers

132 (Al, Ga) As layer

14 top electrodes

15 metal gratings

Embodiment

Below by specific instantiation explanation embodiments of the present invention, those skilled in the art can understand other advantages of the present invention and effect easily by the disclosed content of this specification.The present invention can also be implemented or be used by other different embodiment, and the every details in this specification also can be based on different viewpoints and application, carries out various modifications or change under the spirit of the present invention not deviating from.

See also Fig. 1 a to Fig. 3.Need to prove, the diagram that provides in the present embodiment only illustrates basic conception of the present invention in a schematic way, satisfy only show in graphic with the present invention in relevant assembly but not component count, shape and size drafting when implementing according to reality, kenel, quantity and the ratio of each assembly can be a kind of random change during its actual enforcement, and its assembly layout kenel also may be more complicated.

Embodiment 1

Shown in Fig. 1 a～1b, the invention provides a kind of surface phasmon coupling Terahertz quantum well detector, be used for the detection of incident photon, comprise at least: Semiconductor substrate 11; Bottom electrode 12 is incorporated into described Semiconductor substrate 11; Multi-quantum pit structure 13 is incorporated into described bottom electrode 12, comprises a plurality of stacked GaAs/ (Al, Ga) As quantum well, and described GaAs/ (Al, Ga) As quantum well is comprised of GaAs layer 131 and (Al, Ga) As layer 132; Top electrode 14 is incorporated into described multi-quantum pit structure 13, and described top electrode 14 is 1.0 * 10 for electron adulterated concentration ¹⁷～5.0 * 10 ¹⁷/ cm ³The n-GaAs layer that mixes of N-shaped, its thickness is 0.2～0.6 μ m; Metal grating 15, be incorporated into described top electrode 14, comprise a plurality of spaced bonding jumpers, the cycle of described metal grating 15 is 10～30 μ m, the width of described bonding jumper is 5～15 μ m, be used for to realize the polarity deflection of incident photon, and make electron interaction in described incident photon and the described top electrode 14 with at described top electrode 14 surface formation surface phasmons.

In an embodiment, described top electrode 14 is 3.0 * 10 for electron adulterated concentration ¹⁷～5.0 * 10 ¹⁷/ cm ³The cycle of described metal grating 15 is 15～25 μ m, and the width of described bonding jumper is 8～12 μ m.The n-GaAs layer that described bottom electrode 12 mixes for N-shaped, and its electron adulterated concentration is 1.0 * 10 ¹⁷～5.0 * 10 ¹⁷/ cm ³The mol ratio of Al is 1%～5% in described GaAs/ (Al, Ga) the As quantum well.The quantity of GaAs/ (Al, Ga) the As quantum well in the described multi-quantum pit structure 13 is 20～40.The width of described GaAs/ (Al, Ga) As quantum well is 10～20nm.The material of described metal grating 15 is the alloy of Al, Cu, Au, Pt or its combination in any.The thickness of described metal grating 15 is 0.2～0.8 μ m.

Embodiment 2

Shown in Fig. 1 a～3, the present embodiment provides a kind of surface phasmon coupling Terahertz quantum well detector, is used for the detection of incident photon, comprises at least: Semiconductor substrate 11; Bottom electrode 12 is incorporated into described Semiconductor substrate 11; Multi-quantum pit structure 13 is incorporated into described bottom electrode 12, comprises a plurality of stacked GaAs/ (Al, Ga) As quantum well; Top electrode 14 is incorporated into described multi-quantum pit structure 13, and described top electrode 14 is 5.0 * 10 for electron adulterated concentration n ¹⁷/ cm ³The n-GaAs layer that mixes of N-shaped, its thickness a is 0.4 μ m; Metal grating 15, be incorporated into described top electrode 14, comprise a plurality of spaced bonding jumpers, the period p of described metal grating 15 is 16 μ m, the width s of described bonding jumper is 8 μ m, be used for to realize the polarity deflection of incident photon, and make electron interaction in described incident photon and the described top electrode 14 with at described top electrode 14 surface formation surface phasmons.

In an embodiment, described Semiconductor substrate 11 is the GaAs substrate, and certainly, in other embodiments, described substrate also may be the Semiconductor substrate 11 of all expectations such as Si substrate.The n-GaAs layer that described bottom electrode 12 mixes for N-shaped, and its electron adulterated concentration is 1.0 * 10 ¹⁷The mol ratio of Al is 2.2% in described GaAs/ (Al, Ga) the As quantum well.The quantity of GaAs/ (Al, Ga) the As quantum well in the described multi-quantum pit structure 13 is 30.The width of described GaAs/ (Al, Ga) As quantum well is 15nm.Quantum well center 10nm region doping concentration 4.0 * 10 ¹⁶/ cm ³, the material Pt of described metal grating 15 certainly, in other embodiments, also can be the metal structure of Al, Au alloy or overlapping all expections that form of multiple layer metal.The thickness of described metal grating 15 is 0.5 μ m.

Such as Fig. 2～shown in Figure 3, the present embodiment has provided the field strength distribution after photon incident of surface phasmon coupling Terahertz quantum well detector of the present invention and the numerical computations that improves multiple with respect to the efficient of traditional miter angle coupling, and is specific as follows:

The relative dielectric constant of the n-GaAs layer that described N-shaped mixes can be expressed as:

${\mathrm{\&epsiv;}}_2=\frac{{\mathrm{\&omega;}}_{\mathrm{TO}}^2({\mathrm{\&epsiv;}}_s-{\mathrm{\&epsiv;}}_{\&infin;})}{{\mathrm{\&omega;}}_{\mathrm{TO}}^2-{\mathrm{\&omega;}}^2-i{\mathrm{\&Gamma;}}_{\mathrm{TO}}}+{\mathrm{\&epsiv;}}_{\&infin;}[1-\frac{{\mathrm{\&omega;}}_{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="HDA0000149381690000021.png,HDA0000149381690000022.png"\; state="\{\{state\}\}">p</figure-callout>}}^2}{\mathrm{\&omega;}(\mathrm{\&omega;}+i{\mathrm{\&Gamma;}}_p)}]---\left(1\right)$

ω in the formula _TO=5.04 * 10 ¹³Hz is horizontal optical phonon angular frequency among the GaAs, ε _s=12.85 and ε _∞The static state of the=10.88th, GaAs and high-frequency dielectric constant, Γ _TO=3.8 * 10 ¹¹Hz is the horizontal optical phonon relaxation factor, and i is the imaginary unit of plural number, Γ _p=3.0 * 10 ¹¹Hz is the free carrier phasmon relaxation factor.

Be electronics plasmon resonance frequency, wherein n is electron adulterated concentration, and e is the electron charge number, ε ₀Permittivity of vacuum, m ^*=0.067, be electron effective mass.

The GaAs dielectric constant is in the described quantum well:

${\mathrm{\&epsiv;}}_3={\mathrm{\&epsiv;}}_{\&infin;}+\frac{{\mathrm{\&omega;}}_{\mathrm{TO}}^2({\mathrm{\&epsiv;}}_s-{\mathrm{\&epsiv;}}_{\&infin;})}{{\mathrm{\&omega;}}_{\mathrm{TO}}^2-{\mathrm{\&omega;}}^2-i{\mathrm{\&Gamma;}}_{\mathrm{TO}}}---\left(2\right)$

In the Terahertz frequency range, higher doping content n can make ε ₃＜0, theoretical according to surface phasmon at this moment, in n-GaAs layer that air-N-shaped mixes-GaAs quantum well three-decker, can produce surface phasmon, its dispersion equation is:

$e^{-4k_{1}a}=\frac{{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="HDA0000149381690000022.png"\; state="\{\{state\}\}">k</figure-callout>}}_1/{\mathrm{\&epsiv;}}_1+{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="HDA0000149381690000021.png,HDA0000149381690000022.png"\; state="\{\{state\}\}">k</figure-callout>}}_2/{\mathrm{\&epsiv;}}_2}{{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="HDA0000149381690000022.png"\; state="\{\{state\}\}">k</figure-callout>}}_1/{\mathrm{\&epsiv;}}_1-{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="HDA0000149381690000021.png,HDA0000149381690000022.png"\; state="\{\{state\}\}">k</figure-callout>}}_2/{\mathrm{\&epsiv;}}_2}\&times;\frac{{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="HDA0000149381690000022.png"\; state="\{\{state\}\}">k</figure-callout>}}_1/{\mathrm{\&epsiv;}}_1+k_3/{\mathrm{\&epsiv;}}_3}{{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="HDA0000149381690000022.png"\; state="\{\{state\}\}">k</figure-callout>}}_1/{\mathrm{\&epsiv;}}_1-k_3/{\mathrm{\&epsiv;}}_3}---\left(3\right)$

In the formula I=1,2,3, represent respectively air, N-shaped GaAs-GaAs layer and GaAs layer, k ₁, k ₂, k ₃Be respectively air, the n-GaAs layer of N-shaped doping and the wave vector in the GaAs layer, ε ₁, ε ₂, ε ₃Be respectively the dielectric constant of air, N-shaped n-GaAs layer and GaAs layer, β is the surface phasmon propagation constant, k ₀=ω/c is vacuum photon wave vector, and ω and c are vacuum photon angular frequency and vacuum light speed.

Because the grating bonding jumper is finite width and contacts with 14 layers of top electrodes, the n-GaAs layer that air-N-shaped is mixed-GaAs quantum well three-decker has larger disturbance.So the wave vector that grating provides is expressed as β=2 π m/ (p-s), m=± 1, ± 2..., the electron adulterated concentration n of given top electrode, can obtain the dielectric function of N-shaped GaAs according to equation (1), the thickness a of the n-GaAs layer that mixes of selected N-shaped then can obtain the ω of surface phasmon-β dispersion relation according to equation (3), then determine to obtain wave vector behind the grating parameter, thereby obtain the frequency of resonance absorption mould.Adopt at last the Numerical Calculation of Electromagnetic Fields based on Finite Element Method, can obtain the field strength distribution in Terahertz quantum well detector Multiple Quantum Well zone, and the efficient that provides with respect to traditional miter angle coupling improves multiple.Band structure and photoresponse spectrum according to above data simultaneous solution Schrodinger equation and Poisson's equation design Terahertz quantum well detector, change the width of metal grating cycle, bonding jumper, the electron adulterated concentration of top electrode and the thickness of top electrode peak response frequency and surface phasmon introducing resonance absorption mould are complementary, to obtain the Terahertz quantum well detector Multiple Quantum Well detector of function admirable in certain wave frequency scope.

As shown in Figure 2, the direction of definition vertical metal grating planar is the z direction, can find out E from Fig. 2 (a) _zBe the mould that dies that declines in the z direction, the surface phasmon that the grating coupling forms forms standing wave between bonding jumper, in detector multi-quantum pit structure zone larger E is arranged _zThere is scarcely uniformity in field strength distribution in the z direction.Curve is tried to achieve by dispersion equation (3) among Fig. 2 (b), round dot is based on the finite element numerical method and tries to achieve, its wave vector is according to 2 π m/ (p-s), m=± 1, ± 2... determines, by curve among the figure and round dot as seen, dispersion equation (3) and mutually coincide good based on the resonance frequency that the finite element numerical method obtains.By among the figure as can be known, the resonance frequency of surface phasmon of the present invention coupling Terahertz quantum well detector is: 3.10,3.96,4.27,4.45,4.55,4.60 and 4.63THz.Corresponding at the 3.96THz formant | E _z| ²Maximum, therefore with the peak response Frequency Design of Terahertz quantum well detector at 4.0THz.

As shown in Figure 3, the Al component is 2.2% in the quantum well of surface phasmon coupling Terahertz quantum well detector of the present invention, and quantum well width is 15nm, and quantum well center 10nm region doping concentration is 4.0 * 10 ¹⁶/ cm ³Scheming right coordinate is miter angle coupling normalization | E _z| ²With frequency relation, left side coordinate is of the present invention | E _z| ²With miter angle coupling | E _z| ²Ratio and frequency relation.The 2nd subband of quantum well is in the position a little less than barrier height, make the 1 2nd intersubband that larger sub-band transition dipole moment be arranged, under suitable applying bias, the optical excitation electronics on the 2nd subband can be transferred to continuous state by tunnelling and scattering very soon simultaneously, forms photoelectric current.Peak response frequency and the surface plasmon resonance frequency major part of optogalvanic spectra are overlapping, guaranteed that surface phasmon coupling Terahertz quantum well detector has very high coupling efficiency, under the online temper band absorbing state, its peak value coupling efficiency is more than 30 times of traditional miter angle coupling, in the situation of the complexity that does not increase the device preparation, greatly improve the service behaviour of Terahertz quantum well detector.

In sum, surface phasmon coupling Terahertz quantum well detector of the present invention comprises: Semiconductor substrate, bottom electrode, multi-quantum pit structure, top electrode and metal grating.Described metal grating is used for realizing the polarity deflection of incident photon, adjust the cycle of described metal grating, the width of bonding jumper and the electron adulterated concentration of top electrode, the thickness of top electrode, can make electron interaction in incident photon and the described top electrode to form surface phasmon in described upper electrode surface.Because thickness of detector only is 2～5 μ m, be in the sub-wavelength scope in the Terahertz frequency range, thereby the evanescent wave that surface phasmon is corresponding can improve device subband absorption efficiency at the resonance frequency place, and improve response device rate and working temperature.So the present invention has effectively overcome various shortcoming of the prior art and the tool high industrial utilization.

Above-described embodiment is illustrative principle of the present invention and effect thereof only, but not is used for restriction the present invention.Any person skilled in the art scholar all can be under spirit of the present invention and category, and above-described embodiment is modified or changed.Therefore, have in the technical field under such as and know that usually the knowledgeable modifies or changes not breaking away from all equivalences of finishing under disclosed spirit and the technological thought, must be contained by claim of the present invention.

Claims (9)

1. a surface phasmon coupling Terahertz quantum well detector is used for the detection of incident photon, it is characterized in that, comprises at least:

Semiconductor substrate;

Bottom electrode is incorporated into described Semiconductor substrate;

Multi-quantum pit structure is incorporated into described bottom electrode, comprises a plurality of stacked GaAs/ (Al, Ga) As quantum well;

Top electrode is incorporated into described multi-quantum pit structure, and the described very electron adulterated concentration that powers on is 1.0 * 10 ¹⁷～5.0 * 10 ¹⁷/ cm ³The n-GaAs layer that mixes of N-shaped, its thickness is 0.2～0.6 μ m;

Metal grating, be incorporated into described top electrode, comprise a plurality of spaced bonding jumpers, the cycle of described metal grating is 10～30 μ m, the width of described bonding jumper is 5～15 μ m, be used for to realize the polarity deflection of incident photon, and make electron interaction in described incident photon and the described top electrode with at described upper electrode surface formation surface phasmon.

2. surface phasmon according to claim 1 coupling Terahertz quantum well detector, it is characterized in that: the described very electron adulterated concentration that powers on is 3.0 * 10 ¹⁷～5.0 * 10 ¹⁷/ cm ³

3. surface phasmon according to claim 1 coupling Terahertz quantum well detector, it is characterized in that: the cycle of described metal grating is 15～25 μ m, the width of described bonding jumper is 8～12 μ m.

4. surface phasmon according to claim 1 coupling Terahertz quantum well detector, it is characterized in that: described bottom electrode is the n-GaAs layer that N-shaped mixes, and its electron adulterated concentration is 1.0 * 10 ¹⁷～5.0 * 10 ¹⁷/ cm ³

5. surface phasmon according to claim 1 coupling Terahertz quantum well detector, it is characterized in that: the mol ratio of Al is 1%～5% in described GaAs/ (Al, Ga) the As quantum well.

6. surface phasmon according to claim 1 coupling Terahertz quantum well detector, it is characterized in that: the quantity of GaAs/ (Al, Ga) the As quantum well in the described multi-quantum pit structure is 20～40.

7. surface phasmon according to claim 1 coupling Terahertz quantum well detector, it is characterized in that: the width of described GaAs/ (Al, Ga) As quantum well is 10～20nm.

8. surface phasmon according to claim 1 coupling Terahertz quantum well detector, it is characterized in that: the material of described metal grating is the alloy of Al, Cu, Au, Pt or its combination in any.

9. surface phasmon according to claim 1 coupling Terahertz quantum well detector, it is characterized in that: the thickness of described metal grating is 0.2～0.8 μ m.

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