CN103325862A - Two-tone quantum well infrared light detector - Google Patents

Abstract

The invention discloses a two-tone quantum well infrared light detector which is based on a surface plasma body and the raster scattering effect. The two-tone quantum well infrared light detector comprises a semiconductor substrate layer, a buffering layer located on a substrate, a lower contact layer located on the buffering layer and a bottom electrode of a connection detector of the lower contact layer, a first quantum well layer located on the lower contact layer, a middle contract layer located on the first quantum well layer and a middle electrode in a connection detector of the middle contact layer, a second quantum well layer located on the middle contact layer, an upper contact layer located on the second quantum well layer and an upper electrode of a connection detector of the upper contact layer, and a metal layer located on the upper contact layer. A grating structure is arranged in the metal layer. The two-tone quantum well infrared light detector has the advantages that optical coupling is performed through a metal sub-wavelength raster, and effective absorption of vertical incidence light by a two-tone quantum well structure is achieved by utilizing the generated surface plasma body and the raster scattering effect.

Description

A kind of double color quantum trap infrared detector

Technical field

The present invention relates to the infrared detector field, particularly a kind of double color quantum trap infrared detector based on surface plasma and grating scattering effect.

Background technology

Infrared Detectors is the core component of infrared system, thermal imaging system, and quantum trap infrared detector is because the material of its foundation has ripe growth technique and manufacture craft, makes it in high uniformity, large tracts of land, infrared focus plane is stared and obtained in the system using widely cheaply.All have wide application and huge social, economic benefit at military, medical treatment and other field.Now become the optical semiconductor detector of primary study, development in the world.Yet along with developing rapidly of modern semiconductor technology, only absorb monochromatic infrared detector and the face battle array of a wavelength, not satisfied people uses more high integration and multi-purpose requirement of device, need to realize dual-band window, multiobject Infrared Detectors just needs the higher dual-color red external detector of integrated level.

Quantum trap infrared detector can carry out artificial cutting by changing potential well width and barrier height, realizes the controlled of response wave length, utilizes the intersubband transitions of quantum well to realize the photoelectric absorption conversion.According to the selection rule of quantum well sub-band transition, have only direction of an electric field to be parallel to the light wave ability exciton band-to-band transition of the direction of growth of quantum well.Yet detector is mainly used in the normal incidence condition, need by certain coupled modes, make incident light produce the light component that is parallel to the quantum well direction by modes such as refraction or diffraction, thereby photon energy is coupled to quantum well layer, and common coupled modes have peacekeeping two-dimensional grating coupling, 45 degree angle lap couplings, unordered grating and ripple coupling etc.Yet these methods have not only increased the difficulty of technology, have also limited the applicability of device.For overcoming this problem, employing has periodicity metal aperture battle array structure as optical coupling structure, utilize the surface plasma bulk effect, make the light of vertical incidence change the electromagnetic wave of propagating along the metal surface into, realized the effective absorption of quantum well structure to the vertical incidence light wave.

In the technology of disclosed utilization periodicity metal aperture structure as the quantum well Light Coupled Device, it is main that what use is that the hole battle array structure of layer of metal is coupled to the single wavelength quantum well detector, though this coupled apparatus has improved the absorption efficiency of detector, yet do not consider that the grating scattering effect is to the optimization application to the double color quantum trap detector.

Summary of the invention

For overcoming the problems referred to above, the present invention utilizes surface plasma bulk effect that metal aperture battle array structure periodically produces long-wave band and the grating scattering effect of medium wave band is combined, and has realized utilizing different effect to the quantum trap infrared detector of two kinds of band detections.The objective of the invention is to be to propose that a kind of structural design is flexible, the simple quantum trap infrared detector spare structure of preparation technology, satisfying the vertical incidence light wave, and two waveband is carried out the needs of light wave detection application simultaneously.

The present invention is based on the intersubband transitions principle of quantum-well materials and works, and is arranged in the energy of the Electron absorption infrared wavelength of quantum well conduction band, and the ground state transition from the conduction band subband is to excitation state, and forms photoelectric current under the effect of electric field outside.But because the selection rule of intersubband transitions in the quantum well, the light wave that has only direction of an electric field to be parallel to the quantum trap growth direction just can excite sub-band transition, namely can't absorb vertical incidence light.The present invention utilizes the mudulation effect of surface plasma and grating scattering, and electric field intensity is carried out the polarization state modulation perpendicular to the incident light wave of quantum trap growth direction, makes it produce electric field intensity along quantum trap growth direction polarization, to satisfy the quantum well acceptance condition.

Two-color quantum well infrared detector 100 based on surface plasma and grating scattering effect provided by the present invention, it comprises layer of semiconductor substrate layer 108; One is positioned at the resilient coating 107 on the described substrate; One is positioned at the following contact layer 106 on the described resilient coating, and the bottom electrode of this layer connection detector; One is positioned at first quantum well layer 105 on the described contact layer down; One is positioned at the middle contact layer 104 on the described quantum well layer, and the target of this layer connection detector; One is positioned at second quantum well layer 103 on the described middle contact layer; One is positioned at the last contact layer 102 on the described quantum well layer, and the top electrode of this layer connection detector; One is positioned at the described metal level of going up on the contact layer 101, has optical grating construction in this metal level.

Advantage of the present invention is that the present invention utilizes periodically surface plasma bulk effect and the grating scattering effect of metal aperture battle array, makes quantum well detector to survey simultaneously two kinds of wave bands; It carries out optical coupling by the metal sub-wavelength grating, utilizes the surface plasma and the light scattering effect that produce, has realized the effective absorption of double color quantum trap structure to vertical incidence light.

Description of drawings

Fig. 1 among the present invention based on the double color quantum trap infrared detector structural representation of surface plasma and grating scattering effect.

Fig. 2 is the structural representation of periodicity metal aperture battle array in the metal level optical grating construction among the present invention.

Fig. 3 is the difformity schematic diagram of periodicity metal aperture battle array among the present invention.

The spectrogram that Fig. 4 produces to the quantum well double-color detector spare for incident light vertical irradiation among the present invention.

The vertical direction distribution map of the electric field that Fig. 5 produces to the quantum well double-color detector spare for incident light vertical irradiation among the present invention.

Fig. 6 is for strengthening schematic diagram at distance layer on surface of metal 250nm place vertical direction electric field among the present invention.

The scattered light intensity schematic diagram that Fig. 7 obtains to the quantum well double-color detector spare for incident light vertical irradiation among the present invention.

Embodiment

For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in further detail.

Fig. 1 shows among the present invention the two-color quantum well infrared detector structural representation based on surface plasma and grating scattering effect.As shown in Figure 1, described two-color quantum well infrared detector 100 comprises layer of semiconductor GaAs substrate layer 108; One is positioned at the GaAs resilient coating 107 on the described substrate; Contact layer 106 under one GaAs that is positioned on the described resilient coating, and the bottom electrode of this layer connection detector; One is positioned at the InGaAs/AlGaAs quantum well layer 105 on the described contact layer down; Contact layer 104 in the middle of one GaAs that is positioned on the described quantum well layer, and the target of this layer connection detector; One is positioned at the GaAs/AlGaAs quantum well layer 103 on the described middle contact layer; One GaAs that is positioned on the described quantum well layer goes up contact layer 102, and the top electrode of this layer connection detector; One is positioned at the described metal level of going up on the contact layer 101, has optical grating construction in this metal level.

The material of metal level 101 is that incident light wave is absorbed very weak metal, and has very big negative index, as Au, Ag, Al etc.; And metal layer thickness is 20nm-2000nm.Optical grating construction to metal level 101 also has certain requirement.

Fig. 2 is the optical grating construction exemplary plot of metal level according to one preferred embodiment of the present invention.As shown in Figure 2, the optical grating construction on the described metal level is periodic metal aperture battle array, preferably adopts periodically metal circular pore structure, the deep equality in its metal layer thickness and hole.

Fig. 3 shows the difformity figure of the periodicity Kong Zhen of metal level among the present invention.As shown in Figure 3, it shows different cycles that hole battle array periodically may adopt and the shape in hole.(a) be that periodically metal aperture is for circular, by square periodic arrangement, the line of the central point of its adjacent four circular holes is that a length of side is the square of x; (b) be that periodically metal aperture is square, by square periodic arrangement, the line of the central point of its adjacent four square holes is square; (c) for metal aperture periodically be rectangle by the parallelogram periodic arrangement, the line of the central point of its adjacent four rectangles is parallelogram; (d) for the periodicity metal aperture comprises positive trigonometric sum inverted triangle, its equilateral triangle and del are alternately arranged by row, press the rectangle periodic arrangement.In addition, also can adopt the shape in regular polygon, irregular polygon or other complicated holes, or the combination of several shapes in these shapes; And the cycle of metal aperture battle array also can adopt equilateral triangle, del, regular polygon to arrange, or these several compound arrangement modes that rearrange.

InGaAs/AlGaAs quantum well layer 105 and GaAs/AlGaAs quantum well layer 103 are based on the quantum well layer of conduction band intersubband transitions, can be the individual layer quantum well layers, or multi layer quantum well.And has doping content: 10 ¹⁵-10 ¹⁹/ cm ³, make that ground state level has enough carrier numbers in the quantum well, intersubband transitions can take place when charge carrier absorbs light-wave energy.The center of InGaAs/AlGaAs quantum well layer 105 correspondences survey wavelength be in infrared (medium wave) wave band, wave-length coverage at 3 microns to 6 micrometer ranges.It is far infrared (long wave) wave band that wavelength is surveyed at the center of GaAs/AlGaAs quantum well layer 103 correspondences, wave-length coverage at 8 microns in 15 micrometer ranges.

Incident light wave 109 wavelength comprise the mid and far infrared wave band of required detection, on the direction perpendicular to semiconductor GaAs substrate surface 108 and InGaAs/AlGaAs quantum well layer 105 and GaAs/AlGaAs quantum well layer 103 planes, from the 108 1 side incidents of GaAs semiconductor substrate layer, the photon that incident light wave 109 comprises passes GaAs semiconductor substrate layer 108, GaAs resilient coating 107, contact layer 106 under the GaAs, InGaAs/AlGaAs quantum well layer 105, contact layer 104 in the middle of the GaAs, GaAs/AlGaAs quantum well layer 103, the last contact layer 102 of GaAs, be directly incident on metal level 101, finally absorbed by quantum well layer 103 and quantum well layer 105.

Fig. 4 is the resulting spectrum to the quantum well double-color detector spare of incident light vertical irradiation among the present invention, (a) in solid line be reflectance spectrum, dotted line is transmission spectrum; (b) be the structure absorption spectra, be defined as absorptivity=1-transmissivity-reflectivity.The stronger absworption peak in one place is arranged near 9 microns as seen from the figure, be the surface plasma peak.Long wavelength's photon forms surface plasma 110 at upper surface and/or the lower surface of metal level 101; The plasma 110 that forms has bigger vertical electric field component Ez at GaAs/AlGaAs quantum well layer 103 places, this vertical electric field can excite the transition of the charge carrier generation intersubband in the GaAs/AlGaAs quantum well 103, makes energy be absorbed by GaAs/AlGaAs quantum well layer 103.

The vertical direction distribution map of the electric field that Fig. 5 obtains to the quantum well double-color detector spare for incident light vertical irradiation among the present invention.As shown in Figure 5, be the Ez field pattern at the 250nm place that (is parallel to metal layer plane, i.e. the xy face) on semiconductor one lateral extent metal level 101 surfaces in (a); (b) be at the Ez field pattern of metal aperture central vertical in metal layer plane (being the yz face).

The schematic diagram of Fig. 6 for strengthening at distance layer on surface of metal 250nm place electric field among the present invention.As shown in Figure 6, it is the electric field enhancing＜Ez of 250nm place that (is parallel to metal layer plane, i.e. the xy face) on semiconductor one lateral extent metal level 101 surfaces ²The E0 of 〉/＜ ²The result diagram that calculates, wherein E0 is the electric field strength of incident light,＜Ez ²The E0 of 〉/＜ ²Can reach more than 30 times.According to the selection rule of quantum well intersubband transitions, quantum well only absorbs the electric field Ez perpendicular to the quantum well in-plane, therefore＜and Ez ²The E0 of 〉/＜ ²Raising represent that the present invention can improve the performance of quantum trap infrared detector.

And scattering effect takes place on the surface of metal level 101 in the photon of the short wavelength in the incident light, and scattered light is propagated along all directions; Scattered light passes GaAs and goes up contact layer 102, GaAs/AlGaAs quantum well layer 103, the middle contact layer 104 of GaAs, arrive in the quantum well layer 105, the non-zeroth order scattered light has certain scattering angle, can excite the charge carrier generation intersubband transitions in the InGaAs/AlGaAs quantum well layer 105, make energy be absorbed by InGaAs/AlGaAs quantum well layer 105.

Fig. 7 is the scattered light intensity schematic diagram to the quantum well double-color detector spare of incident light vertical irradiation among the present invention.As shown in Figure 7, it shows the scattering strength of different wave length, as seen in 3 microns to 6 microns medium wave scope very strong scattering is arranged, and can satisfy the detection demand to middle-infrared band.

Two-color quantum well infrared detector described in the present invention adopts the metal semiconductor interface structure, the metal level that namely has optical grating construction, its light that can make vertical incidence is at metal semiconductor interface place excitating surface plasma ripple, it is a kind of electromagnetic wave of non-radiative state, is bound in the inter metal dielectric near interface.The surface plasma bulk-mode can be adjusted by the cycle that changes the metal aperture battle array, because institute's excited surface plasma intensity is along decaying away from excitating surface direction exponentially, so need be nearer from metal level 101 surfaces for designed long wavelength's quantum well 103 absorption regions, in the near field range of near interface, surface plasma wave has humidification to electric field, makes in the metal structure that sub-band transition has enough stiffness of couplings in the surface plasma and quantum well.In semiconductor layer, direction of an electric field is based on the Z direction perpendicular to the interface simultaneously, and this has satisfied the selection rule requirement of the intersubband transitions of quantum well structure.

Exciting of the surface plasma bulk-mode at the interface that metal level contacts with contact layer 102 must be satisfied specific wave vector condition, can not simply excite by incident light irradiation smooth surface.In metal level 101, adopt sub-wavelength cyclic array structure among the present invention, it is the wavelength that cycle of optical grating construction of metal level 101, we will survey less than far infrared band, periodic array structure can provide extra wave vector, reaches the wave vector coupling with this, thus excitating surface plasma.The wave vector matching condition requires:

${\stackrel{\→}{k}}_{\mathrm{spp}}=\stackrel{\→}{k}\sin \mathrm{\θ}\±i\·{\stackrel{\→}{g}}_x\±j\·{\stackrel{\→}{g}}_y---\left(1\right)$

Wherein

With

Be respectively the wave vector of surface plasma wave resultant incident light wave in last contact layer 102 semi-conducting materials, θ is the incidence angle of incident light wave.

Be the unit Prague wave vector in x, y direction that the layer on surface of metal optical grating construction provides, i and j are integer.There is following relation in addition:

$\left|\stackrel{\→}{k}\right|=\frac{2\mathrm{\π}\sqrt{{\mathrm{\ϵ}}_s}}{\mathrm{\λ}}---\left(2\right)$

$\left|{\stackrel{\→}{k}}_{\mathrm{spp}}\right|=\frac{2\mathrm{\π}}{\mathrm{\λ}}\sqrt{\frac{{\mathrm{\ϵ}}_m{\mathrm{\ϵ}}_s}{{\mathrm{\ϵ}}_m+{\mathrm{\ϵ}}_s}}---\left(3\right)$

$\left|{\stackrel{\→}{g}}_x\right|=\left|\frac{2\mathrm{\π}}{\stackrel{\→}{P_x}}\right|---\left(4\right)$

$\left|{\stackrel{\→}{g}}_y\right|=\left|\frac{2\mathrm{\π}}{\stackrel{\→}{P_y}}\right|---\left(5\right)$

Wherein, λ is the incident light wave wavelength of far infrared band in a vacuum, is corresponding absorbing wavelength in the quantum well layer 103, ε _mAnd ε _sBe respectively the dielectric constant of metal level and the last contact layer 102 that contacts with metal level.P _xAnd P _yBe respectively periodicity Kong Zhen in the cycle of x, y direction.Therefore when the target wavelength of detection be the far infrared band wavelength X of incident light wave when determining, can choose suitable periodicity Kong Zhen at the cycle P of x, y direction according to following formula _xAnd P _y, determine the parameter of Kong Zhen, the parameter of described Kong Zhen comprises the cycle of cyclic array and the parameters such as size in hole.

The optical grating construction of metal level has traditional grating scattering effect for the infrared light of medium wave band when exciting the surface plasma of long-wave band, can make the light of middle infrared wavelength that the scattering of each grade time takes place, and quantum well layer can be away from the metal surface.(m, n) the inferior scattering angle α of level can calculate according to the grating scattering formula:

$\sin \mathrm{\α}=\frac{\mathrm{\λ}}{\sqrt{{\mathrm{\ϵ}}_s}}|\frac{m}{\stackrel{\→}{P_x}}+\frac{n}{\stackrel{\→}{P_y}}|---\left(6\right)$

Wherein,

With

For along x, the unit vector of y direction, m, n are integer, λ is the wavelength of middle-infrared band, is corresponding absorbing wavelength in the quantum well layer 105.

As seen, the above-mentioned detector that proposes of the present invention comprises semiconductor substrate layer, resilient coating, three contact electrode layers, two kinds to surveying the metal level that wavelength quantum well layers and one deck have sub-wavelength periodicity hole battle array structure with different.Wherein respectively corresponding middle-infrared band and far infrared band of the detection wavelength of two kinds of quantum well layers, and quantum well has certain carrier concentration, and has two energy levels at least; Contact electrode layer connects electrode provides place in circuit and read output signal used.The infrared incident light wave of certain spectrum width is perpendicular to semiconductor layer incident, wherein the light of far infrared wavelength is at metal and semiconductor layer excitating surface plasma at the interface, at the interface because grating effect generation optical diffusion effect, scattered light reflects along different directions the light of middle infrared wavelength at metal and semiconductor layer.The excited surface plasma wave is absorbed near near the far infrared quantum well layer the metal level, and scattered light is absorbed near near the middle infrared quantum trap layer the semiconductor layer.The light that absorbs makes the electronics generation intersubband transitions process of conduction band in the quantum well layer, and the electronics of transition is collected to form current signal under the alive effect outside.

The preferred embodiment of the present invention realizes in the GaAs system, but in using process of the present invention, can realize in semiconductor material system widely, as InP, GaN etc.In the application for practical devices, can the incident light wave 109 of two-color quantum well infrared detector 100 by incidence surface, namely semiconductor substrate surface (108) is introduced dielectric layer and is improved the quantum absorption efficiency of incident light wave at the anti-reflection film of surveying wavelength.

Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; be understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of making, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (10)

1. two-color quantum well infrared detector (100) based on surface plasma and grating scattering effect, it comprises layer of semiconductor substrate layer (108); One is positioned at the resilient coating (107) on the described substrate; One is positioned at the following contact layer (106) on the described resilient coating, and the bottom electrode of this layer connection detector; One is positioned at first quantum well layer (105) on the described contact layer down; One is positioned at the middle contact layer (104) on described first quantum well layer, and the target of this layer connection detector; One is positioned at second quantum well layer (103) on the described middle contact layer; One is positioned at the last contact layer (102) on described second quantum well layer, and the top electrode of this layer connection detector; One is positioned at the described metal level of going up on the contact layer (101), has optical grating construction in this metal level.

2. two-color quantum well infrared detector according to claim 1 (100) is characterized in that, described first quantum well layer (105) and second quantum well layer (103) are based on the quantum well layer of conduction band intersubband transitions.

3. two-color quantum well infrared detector according to claim 1 (100) is characterized in that, described first quantum well layer (105) and second quantum well layer (103) are the individual layer quantum well layers, or multi layer quantum well.

4. two-color quantum well infrared detector according to claim 1 (100) is characterized in that, described first quantum well layer (105) and second quantum well layer (103) have doping content: 10 ¹⁵-10 ¹⁹/ cm ³, make that ground state level has enough carrier numbers in the quantum well, sub-band transition can take place when charge carrier absorbs light-wave energy.

5. two-color quantum well infrared detector according to claim 1 (100), it is characterized in that, the corresponding center of described first quantum well layer (105) and second quantum well layer (103) is surveyed wavelength and is respectively middle-infrared band and far infrared band, wherein the middle infrared wavelength scope 3 microns to 6 micrometer ranges, far infrared wavelength scope at 8 microns in 15 micrometer ranges.

6. two-color quantum well infrared detector according to claim 1 (100), it is characterized in that, optical grating construction on the described metal level (101) is periodic metal aperture battle array, its hole shape is circle, rectangle, triangle, regular polygon, irregular polygon or other complicated shapes, or several shapes compound in these shapes; The metal aperture battle array is arranged according to square, rectangle, parallelogram, equilateral triangle, del, regular polygon, or these several compound arrangement modes that rearrange.

7. two-color quantum well infrared detector according to claim 1 (100) is characterized in that, the material of described metal level (101) is that incident light wave is absorbed very weak metal, and has very big negative index; And metal layer thickness is 20nm-2000nm.

8. two-color quantum well infrared detector according to claim 1 (100), it is characterized in that, in the photon detection process, utilize wavelength to be the incident light wave (109) of mid and far infrared wave band, on the direction perpendicular to semiconductor substrate surface (108) and first quantum well layer (105) and second quantum well layer (103) plane, from semiconductor substrate surface (108) one side incidents, and finally absorbed by quantum well layer.

9. two-color quantum well infrared detector according to claim 8 (100), it is characterized in that, the photon that described incident light wave (109) comprises passes semiconductor substrate layer (108), resilient coating (107), following contact layer (106), first quantum well layer (105), middle contact layer (104), second quantum well layer (103), goes up contact layer (102), is directly incident on metal level (101); Wherein long wavelength's photon forms surface plasma (110) at upper surface and/or the lower surface of metal level (101); The plasma (110) that forms locates to have vertical electric field component (Ez) at second quantum well layer (103), and this vertical electric field makes energy be absorbed by second quantum well layer (103) for the transition of the electronics generation intersubband that excites second quantum well (103); And wherein scattering effect takes place on the surface of metal level (101) in short wavelength's photon, and scattered light is propagated along all directions; Scattered light passes contact layer (102), second quantum well layer (103), middle contact layer (104), arrive in first quantum well layer (105), the non-zeroth order scattered light of certain angle is wherein arranged for the electronics generation intersubband transitions that excites first quantum well layer (105), make energy be absorbed by first quantum well layer (105).

10. two-color quantum well infrared detector according to claim 1 (100) is characterized in that, at the incidence surface introducing dielectric layer of incident light wave with at the anti-reflection film of surveying wavelength.

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