JP6980292B2 - Photodetector - Google Patents

Description

The present invention relates to a photodetector having immediate responsiveness and a wideband spectral region useful for photon detection.

In 1938, Walter Schottky proposed that metal-semiconductor junctions can create potential barriers after thermal equilibrium, and became known as Schottky barriers or Schottky junctions. In the use example of the p-type semiconductor as shown in FIG. 1A, the main carrier is a hole (h +), and each metal and semiconductor has a unique energy band, a Fermi level, and an energy gap before contact. Have. Make the work function of metal (qΦ _m ) smaller than the work function of semiconductor (qΦ _s). The work function is defined as the energy difference between the Fermi level and the vacuum level ( _Evac). Wherein the electron affinity of the semiconductor qx is defined as the energy difference and conduction band (E _c) and the semiconductor vacuum level (E _vac).

As shown in FIG. 1B, when the metal comes into contact with the semiconductor, the Fermi level of the semiconductor becomes lower than the Fermi level of the metal. After the thermal equilibrium, the holes of the p-type semiconductor flow into the metal, and a negative charge remains in the semiconductor. Space charges are formed on both sides of the metal-semiconductor junction to generate _{a built-in electric field (V bi).} When it is necessary to flow holes (h +) of the main carrier of the p-type semiconductor from the semiconductor into the metal, it is necessary to overcome the _{built-in electric field (V bi) of the junction.} When biased, the carrier can overcome the built-in electric field, and the applied bias is called the turn-on voltage. When moving the holes from the metal to the semiconductor, it is necessary to overcome the Schottky barrier of the junction. The curved energy band or energy barrier that impedes the movement of the carrier is called a Schottky junction.

According to the metal-semiconductor junction theory, a Schottky junction is formed by adapting a p-type semiconductor to a metal having a large work function and adapting an n-type semiconductor to a metal having a small work function. The height of the Schottky barrier can be estimated from the IV characteristic curve or the CV characteristic curve.

In 1959, H. Y. Mr. Fan and A. K. When a semiconductor is irradiated with light, Ramdas et al. Excited electrons or holes originally in the valence band of the semiconductor by incident photons and jumped to the conduction band to form electron-hole pairs or hot carriers. Was found to be formed. This mechanism is called intermediate bandgap absorption (MBA). In order to excite the electron-hole pair with the incident light, the energy of the incident photon must be larger than the energy gap of the semiconductor, so that the carrier has sufficient energy to exceed the energy gap of the semiconductor. Acquired and photon current is formed. Today, photodetectors make extensive use of this semiconductor's intermediate bandgap absorption mechanism.

Recent infrared sensors mainly use semiconductors with a small energy gap such as III-V and Ge as an active layer or a detection and absorption material for detecting infrared light with a small photon energy. Although the use of III-V and Ge detectors has become established in the manufacturing process, these materials are more expensive than other materials and the process requires a variety of complex and expensive epitaxial devices. .. The detection principle of these devices mainly uses intermediate bandgap absorption (MBA). The carriers of the semiconductor are excited by the incident light and generate a photocurrent over the bandgap of the semiconductor. Therefore, in order to increase the detection efficiency or the responsiveness of the apparatus, it is necessary to incorporate complex multiple quantum wells (MQWs) or multiple quantum dots (MQDs) of the active layer into these members.

The present invention relates to a photodetector, particularly a wideband photodetector.

According to one embodiment of the invention, the photodetector comprises a semiconductor, an ohm contact electrode, and a metal electrode, wherein the semiconductor comprises one or more microscale or nanoscale plasmon resonance induced structures. The ohm contact electrode forms ohm contact with the first surface of the semiconductor. The metal electrode forms a Schottky contact with the surface of the plasmon resonance induced structure. The carriers of the metal electrode are excited by incident light to form electron-hole pairs or hot carriers, and a photocurrent is formed over the Schottky barrier at the junction between the metal electrode and the semiconductor. Localized surface plasmon resonance (LSPR) is induced on the surface of the plasmon resonance-induced structure by the incident light, and the plasmon decay wave generated by the localized surface plasmon resonance is transmitted to the Schottky junction by a strong proximity field. A large amount of hot carriers are excited to accelerate the response of the photodetector. The plasmon resonance-induced structure comprises a periodic structure for inducing localized surface plasmon resonance, promoting light absorption, and improving the response of the photodetector.

The energy band of the metal before contacting with the semiconductor is illustrated. The energy band of the metal after contact with the semiconductor is illustrated. The photodetector according to the first embodiment of the present invention is illustrated. The IV measurement of the photodetector using gold and platinum as the ohm contact electrode is illustrated. The dark and photocurrents of a photodetector formed of vapor-deposited copper followed by platinum growth are illustrated. The photocurrent response of a copper / p-type silicon element measured by a solar simulator while being irradiated with visible light is illustrated. The photocurrent response of the photodetector operating at 0 bias is illustrated. The absorption spectrum of the copper / p-type silicon photodetector according to the first embodiment of the present invention is illustrated. The response of the copper / p-type silicon photodetector according to the first embodiment of the present invention to incident light of different wavelengths is illustrated. The perspective view of the photodetector which concerns on 2nd Embodiment of this invention is shown. A cross-sectional view of one of the periodic microarray nanostructures of the photodetector according to the second embodiment of the present invention is shown. The manufacturing method of the photodetector which concerns on 2nd Embodiment of this invention is illustrated. SEM images of a top view and a cross-sectional view of an inverted pyramid structure (IPS) after etching with an aqueous potassium hydroxide solution for 20 minutes are shown. The relationship between the line width of the inverted pyramid structure (IPS) and the etching time is illustrated. An inverted pyramid structure (IPS) simulated by the finite element method is illustrated. The simulation result of the localized surface plasmon resonance of the inverted pyramid structure (IPS) when the incident light of a different wavelength is vertically incident on the metal of an IPS photodetector is shown. The relationship between the intensity and the length of the localized surface plasmon resonance (LSPR) of the cavity wall of the inverted pyramid structure (IPS) to which the incident light of different wavelengths shown in FIG. 13 is incident is shown. The relationship between the wavelength of incident light and the length of the cavity wall of the inverted pyramid structure (IPS) induced by localized surface plasmon resonance at various resonance modes is shown. The absorption spectrum of the photodetector according to the comparative example and the second embodiment of the present invention is shown. FIG. 2 illustrates the IV measurement of the dark current of the planar and IPS copper / p-type Schottky photodetectors according to the first and second embodiments of the present invention. The photoelectric response measured with infrared rays of different wavelengths incident on the optical plane and the IPS photodetector is illustrated. After some hot carriers of the photodetector according to the second embodiment of the present invention collide with each other, they acquire energy larger than the Schottky barrier and form a hot air stream beyond the energy barrier. .. The response when the photodetector according to the second embodiment of the present invention operates with an infrared laser of 1550 nm at different incident light intensities and bias voltages is illustrated. A chart showing the relationship between the response and the incident intensity of the photodetector according to the second embodiment of the present invention is shown. The SEM image in which the three-dimensional upright pyramid structure which concerns on one Embodiment of this invention is constructed is shown. The Schottky contact formed by plating a nanosilver film on a flat silicon substrate according to an embodiment of the present invention is illustrated. The response of FIG. 24 when light is incident on the Schottky contact from different angles is illustrated. A simulation of an inverted pyramid structure (IPS) using the finite element method when light changes to enter Schottky contact from a silicon substrate is illustrated. The simulation results of localized surface plasmon resonance when incident light of different wavelengths are vertically incident on a metal of an upright pyramid structure (UPS) are illustrated.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The first embodiment of the present invention provides a photodetector using a metal-semiconductor junction. The photodetector can detect light with an energy smaller than the energy gap of the semiconductor, and generates a photocurrent only when the energy of the incident light is slightly larger than the Schottky barrier.

FIG. 2 illustrates a photodetector 1 according to an embodiment of the present invention. As shown in FIG. 2, the photodetector 1 includes a semiconductor 10, an ohmic contact electrode 12, and a metal electrode 14. The metal electrode 14 includes a Schottky contact electrode 141 and a grid electrode 142. In this embodiment, the semiconductor 10 is p-type silicon, the ohmic contact electrode 12 is made of platinum, and the metal electrode 14 is made of chromium. In some embodiments, the ohmic contact electrode 12 is gold or silver and the metal electrode 14 is copper.

In this embodiment, the semiconductor 10 is a p-type (100) double-sided polished silicon wafer, having a resistance of 5Ω-cm to 10Ω-cm and a thickness of 380μm to 420μm. First, the silicon wafer is cut into a 2.5 cm2 × 2.5 cm2 silicon substrate 10 by a diamond pen. Next, the silicon substrate is immersed in acetone, isopropyl alcohol (IPA), deionized water (DI-water), and methanol in this order, and washed with an ultrasonic cleaner for 15 minutes to remove organic substances and particles on the surface.

Next, a piranha solution _{of sulfuric acid (H 2} SO ₄ ) and hydrogen peroxide (H ₂ O ₂ ) having a volume ratio of 4: 1 is prepared. First, the sulfuric acid is poured into the glass dish, then the hydrogen peroxide is slowly poured into the glass dish, and the solution is heated to 120 ° C. After the gas is generated during the volatilization of the mixture, the silicon substrate 10 is immersed in the solution for 10 minutes. In this step, a thin oxide film grows on the surface of the silicon substrate 10, and foreign matter on the surface is separated from the substrate. Next, the silicon dioxide on the surface of the silicon substrate 10 is removed by the buffer oxide etching (BOE) solution. Finally, the silicon substrate 10 is rinsed with deionized water (DI-water) and dried with nitrogen to complete the cleaning step.

After cleaning, the silicon substrate 10 is placed on an electron beam deposition system (ULVAC) and the metal electrode 14 grows under a pressure of ^{4 × 10 −6 torr.} First, a chromium nanofilm having a thickness of 10 nm to 20 nm grows as a Schottky contact electrode 141 on the upper surface of the silicon substrate 10, and the growth rate is 0.1 Å per second. Next, the chromium nanofilm is coated with a metal shadow mask, and a chromium metal grid 142 having a thickness of 120 nm is formed on the chromium nanofilm at 0.1 Å to 10 nm per second, 0.3 Å to 30 nm per second, and 0.5 Å to 50 nm per second. , And grow at a growth rate of 1 Å to 100 nm per second. Finally, a platinum film having a thickness of 100 nm grows as the ohm contact electrode 12 at the bottom of the p-type silicon substrate, and its growth rate is the same as that of the chrome grid electrode. Then, as shown in FIG. 2, the photodetector 1 is completed. Next, the manufactured photodetector 1 receives an IV characteristic curve of photocurrent and dark current. LabVIEW measurement software is used with the Caseray 2400 SourceMeter to make measurements in a dark box using a 1550 nm, 2 mW infrared laser (Thorlab: LDC1300B model) as a light source.

In another embodiment of the invention, the ohm contact electrode 14 is made of gold (platinum is used to form ohm contact with the p-type silicon, and the photodetector has a preferred forward bias), etc. The member is manufactured of the same material as in the above-described embodiment. Gold and platinum are used as the ohmic contact electrode 14 for the IV measurement of the photodetector shown in FIG. 3, respectively. As shown in FIG. 3, the photodetector has a favorable rectifying effect due to the use of platinum as the ohmic contact electrode 12. When forward biased, a large current is generated, and when reverse biased, it has a small leak current. The turn-on voltage is only about 0.3V, which is characteristic of general purpose Schottky diodes.

As shown in FIG. 2, the metal electrode 14 comprises a Schottky contact electrode 141 made of chromium with a thickness in the range between 10 nm and 20 nm and a grid electrode 142 made of chromium with a thickness of 120 nm. .. In another embodiment, the photodetector has Schottky contact electrodes 141 made of 10 nm and 20 nm chromium, each manufactured separately and their performance compared. Three dark currents and three photocurrents are measured by each element. The measurement results show that the Schottky contact electrode 141 having a thickness of less than 10 nm is suitable for allowing the incident light to enter the active region of the photodetector, and enhances the response performance of the photodetector.

In another embodiment of the invention, the semiconductor 10, the ohmic contact electrode 12, and the metal electrode 14 are made of p-type silicon, platinum, and copper, respectively. The photodetector is manufactured in the same process as described above, and the metal electrode 14 includes a 10 nm copper shotkey contact electrode 141 and a 120 nm chromium grid electrode 142. Further, in order to avoid the influence of the high temperature of the copper nanofilm in the platinum growth, the growth order is changed so that platinum grows after the copper grows. The dark current and the photocurrent of the photodetector are shown in FIG. The performance of the copper / p-type silicon photodetector is close to that of the general-purpose Schottky diode, and the manufactured photodetector has a higher rectifying effect and a smaller turn-on voltage. The photodetector produces a large current when operating in the forward bias region and maintains a small reverse bias when operating in the reverse bias region. Therefore, the problem that a leak current is generated when operating in the reverse bias region can be solved by changing the growth order.

According to one embodiment of the invention, the Schottky barrier is formed in the gold-semiconductor junction, allowing the carriers to flow in only one particular direction, forming a rectifying effect. The p-type silicon wafer used in the present invention has a Fermi level of the theoretical _E F = _-4.952eV, chromium (-4.5eV) or copper (-4.65eV) is selected as the metal electrode To. The Schottky barrier is made of about 0.67 eV chromium / p-type silicon, and a cutoff wavelength of about 1850 nm is measured in the near infrared region. When the Schottky barrier is made of copper / p-type silicon of about 0.52 eV, its cutoff wavelength is about 2384 nm.

FIG. 5 illustrates the optical current of the copper / p-type silicon photodetector measured under visible light illumination by a solar simulator (Atom solar simulator, Sun2000). The dark current of the copper / p-type silicon photodetector exhibits the same rectifying effect characteristics as the general-purpose Schottky diode. When irradiated with sunlight, a clear current difference occurs between the photocurrent and the dark current in the forward bias region or the reverse bias region. Specifically, in the reverse bias region, the photodetector 1 generates a photocurrent of about 40 mA after irradiation.

FIG. 6 also shows that the copper / p-type photodetector also has a recognizable photocurrent response when the photodetector operates at zero bias. Although the response is not as large as in the -2V, -1V, 1V, or 2V regions, the response of the copper / p-type silicon photodetector is highly stable and the dark current of the photodetector fluctuates. Is only 0.1 μA (113 nA) when operating at 0 V, and the response is about 270 nA. The response and variation of this photodetector is more stable than when operating at other voltages.

FIG. 7 illustrates a comparison of the absorption spectra of the copper / p-type silicon photodetector and the silicon substrate. As shown in FIG. 7, the absorption spectrum of the silicon substrate is in good agreement with the theory. Most of the incident light having a wavelength of less than 1107 nm is absorbed by the silicon substrate. At around 1107 nm, the absorption of the silicon substrate rapidly declines, and it becomes difficult to absorb the light having a wavelength exceeding 1107 nm. This result surely agrees with the theoretical value of absorption of the silicon substrate. The silicon has an energy gap of 1.12 eV and has a theoretical absorption wavelength of about 1107 nm. The incident light having an energy of more than 1.12 eV is absorbed by the silicon substrate, and the silicon substrate has high absorbency in the range of 1107 nm to visible light. Photons with energies smaller than the energy gap of the silicon are not absorbed by the silicon substrate, and the absorption of the light having a wavelength of more than 1107 nm by the silicon substrate is close to zero. The absorption spectrum of the copper / p-type silicon photodetector shows wideband absorption, and the absorption for the incident light in the range of 300 nm to 2700 nm is about 40%. In the visible light region, copper reflects the incident light, so that the absorption of the copper / p-type silicon photodetector in the visible light region is lower than that of the silicon substrate. Absorption in the range of 1000 nm to 2300 nm is mainly due to the Schottky barrier. On the metal surface, the incident photons excite the hot carriers, crossing the Schottky barrier of the photodetector to form a hot air stream, and photons in the wavelength range of 1000 nm to 2300 nm are generated by the Schottky barrier. Be absorbed. The incident photons with wavelengths above 2300 nm are absorbed semi-continuously. Since the metal film is a copper film having a thickness of 10 nm, a flat homogeneous film is not formed on the silicon substrate, but a large amount of fine particles are formed. Furthermore, incident light of different wavelengths resonates with a partially fitted resonance region on the surface of the metal film, thereby achieving localized surface plasmon resonance (LSPR).

FIG. 8 illustrates what the copper / p-type silicon photodetector is used to measure the response of incident light of different wavelengths. As shown in FIG. 8, the results are in good agreement with the Emden-Fowler equation, and the copper / p-type silicon photodetector improves responsiveness by applying a slight bias of -5 mV. The measurement results show that when operating at 0 mV or -5 mV, the response of the copper / p-type silicon photodetector gradually declines as the incident light wavelength increases. Further, from the characteristic curve of 5 mV, it is clear that the cutoff wavelength of the copper / p-type silicon photodetector is about 2310 nm. By using this cutoff wavelength, it is calculated from the formula E (eV) = hc / λ = 1240 / (λ (nm)) that the Schottky barrier is about 0.53 eV. As mentioned above, the Schottky barrier of the copper / p-type silicon photodetector is about 0.52 eV based on logical operations. Based on the measurement results of the copper / p-type silicon photodetector, the shotkey barrier is very close to the theoretical value (0.52 eV), which is because the copper / p-type silicon photodetector is the silicon. Prove that the energy of photons lower than the energy gap of is measured reliably. However, the planar copper / p-type photodetector can generate a photocurrent only by internal photoelectron emission absorption (IPA) in the infrared region, and no other auxiliary optimization mechanism is required. When used as a general purpose Schottky photodetector, highly efficient responses are difficult to achieve.

Internal photoelectron emission absorption (IPA) indicates that metal carriers are excited by incident photons and electron-hole pairs or hot carriers are formed and cross the Schottky barrier, thus by an external circuit by physical mechanism. A photocurrent is formed. In order for the hot carriers excited by the incident photons to be absorbed by the Schottky barrier, the energy of the incident light needs to be slightly larger than that of the Schottky barrier, whereby the hot carriers excited by the incident light. Gains enough energy to overcome the Schottky barrier.

FIG. 9A illustrates a photodetector according to a second embodiment of the present invention. As shown in FIG. 9A, the photodetector 2 includes a semiconductor 20, an ohmic contact electrode 22, and a metal electrode 24 (including a Schottky contact electrode). Unlike the photodetector 1 of the first embodiment, the photodetector 2 is characterized in that the semiconductor 20 is not a flat surface but has a periodic microarray nanostructure.

As shown in FIG. 9A, in this embodiment, the periodic microarray nanostructures are three-dimensional inverted pyramid structures (IPS). The dimensions of each pyramid structure are microscale or nanoscale. FIG. 10 illustrates the manufacturing method of the photodetector 2. In this embodiment, the semiconductor is a p-type double-sided polished silicon (100) wafer, having a resistance in the range of 5Ω-cm to 10Ω-cm and a thickness in the range of 380μm to 420μm. First, the silicon wafer is cut into a ^{2.5 cm 2} × 2.5 cm ^{2 silicon substrate 20 by a diamond pen.} Next, the silicon substrate 20 is washed with acetone, isopropyl alcohol (IPA), deionized water (DI-water), and methanol in this order, and finally the surface of the silicon substrate is washed with an ultrasonic cleaner for 15 minutes. Organic substances and fine particles on the surface are removed. Next, as described above, the silicon substrate is washed in order with a piranha solution, a hydrofluoric acid solution, and deionized water, and the silicon substrate 20 is blow-dried by a nitrogen spray gun.

FIG. 9B shows a cross-sectional view of a three-dimensional inverted pyramid structure (IPS) according to an embodiment of the present invention. As shown in FIG. 9B, H indicates the height of the inverted pyramid cavity and L (H) indicates the length of the inverted pyramid cavity wall. As the height H increases, the length L (H) of the cavity wall also increases. The inverted pyramid structure has a fixed period, but each pyramid has various or multiple cavity wall lengths L (H).

FIG. 10 illustrates a method of manufacturing the inverted pyramid structure (IPS) of FIGS. 9A and 9B. As shown in step (a), after cleaning the silicon substrate 20, a silicon dioxide film 21 having a thickness of 500 nm is grown on the upper surface and the bottom surface of the silicon substrate 20 by a plasma CVD apparatus. The silicon dioxide film 21 on the upper surface is used as an etching mask for anisotropic etching with potassium hydroxide, and the silicon dioxide film 21 on the bottom surface is used as a protective layer for etching. The flow rate of the reaction gas is as follows. Si ₄ : 40 sccm; N ₂ O: 160 sccm. The growth temperature is 350 ° C., the growth pressure is 67 Pa, and the growth time is 10 minutes.

As shown in step (b) of FIG. 10, the lithography process is used to define the surface pattern of the silicon substrate 20. First, in the photolithography process, the photoresist (S1813) 23 is uniformly applied to the silicon dioxide film 21 on the upper surface of the silicon substrate 20 by a spin coater. The application parameters are 1000 rpm, 10 seconds / 4000 rpm, and 40 seconds. Subsequently, the coated photoresist 23 is soft-baked at 115 ° C. for 3 minutes. Acetone is used to wash and expose the mask. Next, the silicon substrate 20 is placed on an exposure apparatus, the corners of the silicon substrate 20 are aligned with the corners of the mask, and the mask is exposed for 20 seconds. Then, after the silicon substrate 20 is rotated by 90 ° once after exposure, the mask is closely aligned with the corners of the mask, and the second exposure is performed for 20 seconds. Next, the exposed silicon substrate 20 is immersed in S1813-dicated developed developer MF-319 for 13 seconds. Then, the developed silicon substrate 20 is immersed in deionized water to remove the residual photoresist 23 and the developing solution, and the silicon substrate 20 is dried by a nitrogen spray gun. Finally, the silicon substrate 20 is hard baked by a hot plate at 125 ° C. for 1 minute.

As shown in step (c) of FIG. 10, the silicon substrate 20 is placed on a thermal vapor deposition coater (ULVAC), and a 40 nm-thick chrome film 25 is placed on the upper surface of the silicon substrate 20 in a 4 × ^10-6 torr. It grows at a growth rate of 0.3 Å per minute in a vacuum environment of less than.

As shown in step (d) of FIG. 10, the silicon substrate 20 is immersed in acetone and washed with an ultrasonic cleaner for 30 to 90 minutes, and is on the photoresist 23 and the photoresist 23. The chrome 25 is removed and the remaining chrome 25 is used as a mask in the subsequent dry etching process.

As shown in step (e) of FIG. 10, the etching is performed by a reactive ion etching system (RIE: Plasmaab) at a chamber pressure ^{of 4 × 10 -4 torr.} The flow rate of the reaction gas is 25 sccm for Ar, 25 sccm for CHF ₃ , an operating power of 200 watts, and an etching time of 30 minutes. The silicon substrate 20 is placed in an etching chamber and isotropic etching is performed, and the silicon dioxide 21 is not protected by the chrome mask and is etched in the vertical direction until the silicon dioxide is completely removed, and below the silicon dioxide. The silicon substrate 20 is exposed. The residual silicon dioxide 21 is used in the subsequent anisotropic wet etching process using potassium hydroxide (KOH) as a mask.

As shown in step (f) of FIG. 10, a 15% volume percent concentration of potassium hydroxide etching solution is then prepared. Isopropanol (IPA) and a 45% potassium hydroxide solution are added to the deionized water in a ratio of 1: 5: 15. Isopropanol (IPA) is added due to its low polarity and low surface tension, which creates hydrogen bubbles during the etching and is attached to the structure and is easy to separate from the surface of the silicon. This prevents the silicon dioxide 21 from etching the mask and enhances the uniformity of the etching. After the etching solution is heated to 75 ° C., the silicon substrate 20 is immersed in the etching solution, and isotropic etching is performed for about 10 to 20 minutes to produce the inverted pyramid structure (IPS).

As shown in step (g) of FIG. 10, the silicon substrate 20 is immersed in a buffer oxide etching (BOE) solution to remove the silicon dioxide 21 and the chromium 25 on the upper surface and the bottom surface, and the three-dimensional structure is removed. The inverted pyramid structure is completed. Next, the organic substances, oxides, and metal particles remaining on the surface of the silicon substrate 20 are removed by the piranha solution and the hydrofluoric acid solution (BOE). Next, the silicon substrate 20 is placed on an electron beam vapor deposition system (ULVAC), and the ohmic contact electrode 22 and the metal electrode 24 grow at a chamber pressure of ^{4 × 10 −6 torr.} First, platinum having a thickness of 100 nm grows on the bottom surface of the silicon substrate 20 as an ohmic contact electrode 22. After that, a copper film having a thickness of 8 nm grows as a shotkey contact electrode on the surface of the silicon substrate 20 on the surface IPS, and finally a copper grid electrode having a thickness of 120 nm grows on the surface of the silicon substrate 20 using a shadow mask. Grow in. The metal electrode 24 includes a copper Schottky contact electrode and a copper grid electrode. This completes the photodetector 2 of FIG.

In the manufacturing process described above, the topography of the inverted pyramid structure is highly correlated with the parameters of the lithography process and the potassium hydroxide anisotropic wet etching. FIG. 11 is an SEM image of a top view and a cross-sectional view of the inverted pyramid structure after being etched with an aqueous potassium hydroxide solution for 20 minutes. FIG. 12 illustrates structural parameters showing the relationship between the inverted pyramid nanostructure and the etching time. As shown in FIG. 12, the maximum width of the upper part of each inverted pyramid element reaches 3.8 μm (width), and the gap between two adjacent inverted pyramid elements reaches 300 nm. In another embodiment, the 6 μm and 8 μm period three-dimensional inverted pyramid structures are manufactured by varying the exposure period of the mask, respectively. The optimum potassium hydroxide anisotropic etching times for 6 μm and 8 μm periodic IPS are 22 minutes and 24 minutes, respectively.

In another embodiment of the invention, the three-dimensional upright pyramid structure (UPS) is manufactured with a negative photoresist as opposed to the surface pattern exposed using double exposure and potassium hydroxide etching techniques. To. FIG. 23 shows an SEM image of the manufactured three-dimensional upright pyramid structure.

前記入射電磁波の波長を５００ｎｍ、１０００ｎｍ、１５００ｎｍ、２０００ｎｍ、２５００ｎｍ、３０００ｎｍ、３５００ｎｍ、及び４０００ｎｍにそれぞれ設定する工程と、を含む。前記金属の厚さが実験で用いられた１０ｎｍではなく３０ｎｍに設定されることにより、前記シミュレーションでのメモリー不足の問題が回避される。前記シミュレーション計算が完了すると、次の公式（１）が前記入射電磁波の強度を正常化するために用いられる。

本実施形態では、１０ｎｍの厚さの銅ナノフィルムが、電子ビーム蒸着システムにより前記ＩＰＳ構造の表面に成長し、前記金属表面に金属マイクロアレイナノ構造を完成させる。約０．５２ｅＶのショットキー障壁がある前記金属半導体接合に銅及びｐ型シリコンでショットキー接合が形成される。 In order to promote an understanding of the localized surface plasmon resonance (LSPR) between the incident electromagnetic wave and the metal structure, the three-dimensional FDTD method (3D-FDTD) and the finite element method (FEM) are the resonance of the electromagnetic wave in the IPS structure. Is used to simulate. FIG. 13 illustrates the IPS structure used in the simulation, ^{the step of forming a space having a volume of 4 × 4 × 6 μm 3} (x, y, z), and the perfect matching layer of the six boundary surfaces of the space ( A step of setting PML), a step of forming a silicon-based IPS structure (IPS-Si), and a step of setting a metal nanofilm having a thickness of 30 nm on the surface of a cavity having an inverted pyramid structure.

It includes a step of setting the wavelength of the incident electromagnetic wave to 500 nm, 1000 nm, 1500 nm, 2000 nm, 2500 nm, 3000 nm, 3500 nm, and 4000 nm, respectively. By setting the thickness of the metal to 30 nm instead of the 10 nm used in the experiment, the problem of memory shortage in the simulation is avoided. When the simulation calculation is completed, the following formula (1) is used to normalize the intensity of the incident electromagnetic wave.

In this embodiment, a copper nanofilm having a thickness of 10 nm grows on the surface of the IPS structure by an electron beam vapor deposition system to complete the metal microarray nanostructure on the metal surface. A Schottky junction is formed of copper and p-type silicon in the metal-semiconductor junction having a Schottky barrier of about 0.52 eV.

FIG. 14 illustrates the simulation results in which incident light of 500 nm, 1000 nm, 1500 nm, 2000 nm, 2500 nm, 3000 nm, 3500 nm, and 4000 nm is vertically incident on the metal of the IPS photodetector, respectively. As shown in FIG. 14, when the period of the structure is adjusted to 5 μm to 10 μm, the resonance wavelength is increased to 5000 nm to 10000 nm. As shown in FIG. 14, a strong light confinement effect was observed for all incident wavelengths in the cavity of the Cu-IPS structure, indicating that the structure is a three-dimensional resonant cavity. When the incident wavelength changes, the surface plasmon resonance occurs in cavities in different regions of the Cu-IPS structure. When the incident wavelength is 500 nm, the wavelength of the incident light is short, so the resonance (LSPR) length needs to be shortened, and the matching nanoscale length is located at the bottom of the Cu-IPS structure. The localized surface plasmon resonance is generated. When mid-infrared light with a wavelength of 1500 nm to 4000 nm is incident, the wavelength of the incident light is so long that the localized surface plasmon resonance is generated by the length of the matching microscale near the top of the Cu-IPS structure. Will be done. From all resonance simulations, the localized strong light field of the cavity of the Cu-IPS structure is reliably continuous from the strong proximity field of the metal, thereby causing the localized surface plasmon resonance (LSPR) to the metal surface. Can be clearly seen that is generated. Thus, as shown in FIG. 14, since the IPS structure has geometric properties and lengths of a plurality of cavities, the structure has a resonance cavity length corresponding to the incident light having a wavelength of up to 4 μm. It is demonstrated that it is present and that localized surface plasmon resonance (LSPR) is produced. Further, the IPS structure satisfies the conditions of the two-dimensional geometric symmetry of the unit and the two-dimensional symmetry of the periodic array, and the incident infrared light polarized by X-polarized light and Y-polarized light has a high intensity localized surface plasmon on the surface of the structure. Generate resonance. The IPS structure is polarization-independent of incident light.

FIG. 15 shows the relationship between the intensity of the localized surface plasmon resonance and the length of the cavity with respect to incident light of different wavelengths (see the black arrow in FIG. 13 for data). As shown by the arrows in FIG. 15, for incident light of different wavelengths, the first resonance mode has the shortest length of the resonant metal cavity. As the wavelength of the incident light increases from 500 nm to 4000 nm, the length of the resonant metal cavity in the first resonant mode also increases. Further, for wavelengths in the range of 1000 nm to 4000 nm, the resonance intensity in the first resonance mode decreases as the wavelength of the incident light increases. For example, the resonance intensity of the first resonance mode with respect to the incident light having a wavelength of 1000 nm is stronger than the resonance intensity of the first resonance mode with respect to the wavelength of the incident light of 4000 nm. In order to generate the localized surface plasmon resonance, the incident light having a wavelength of 1000 nm requires a cavity length of 700 nm, and in the case of an IPS structure having a unit width of 4 μm, the incident light intensity is 700 nm. Limited to the length of the cavity. Incident light with a wavelength of 4000 nm requires a cavity length of 2700 nm, and in the case of an IPS structure with a unit width of 4 μm, the incident light intensity is limited to the cavity length of 2700 nm. Therefore, the intensity of the localized surface plasmon resonance of the short-wavelength incident light is stronger than that of the long-wavelength incident light. In order for the long wavelength to have a preferable resonance intensity, it is necessary to increase the period of the IPS structure (for example, the unit width of the IPS structure), and the incident light of the long wavelength obtains a stronger plasma confinement effect.

本発明の他の実施形態において、前記局在表面プラズモン共鳴のシミュレーションは、金／ｐ型ＩＰＳ構造及び銀／ｐ型ＩＰＳ構造を想定して実施される。結果は上述の前記Ｃｕ−ＩＰＳ構造に非常に近似する。よって、前記ＩＰＳ構造での前記入射光の局在表面プラズモン共鳴生成の鍵となるのは複数のキャビティの長さ及び前記構造の周期であることが確認される。ＩＰＳ構造に高強度局在表面プラズモン共鳴を誘起させるには、前記ＩＰＳ構造の周期を目標共鳴波長の約４倍に設計し（４ｎｍの周期のＩＰＳは１０００ｎｍの入射光に対応する）、これにより最良の光閉じ込め効果及び表面プラズモン共鳴強度を達成させる。単一の共鳴金属の長さの局在表面プラズモン共鳴構造は上記方程式（２）乃至（４）を参照して設計され、前記目標波長に要求される共鳴金属の線形長さ及び構造を計算することにより、高強度局在表面プラズモン共鳴構造を獲得することができる。 FIG. 16 shows the relationship between localized surface plasmon resonance induced by the wavelength of incident light and the length of the resonance cavity in various resonance modes. According to FIG. 16, as the wavelength of the incident light increases, so does the length of the resonant metal cavity in the first resonant mode. Here, the relationship between the wavelength and the length of the matching resonant metal cavity is summarized in the following equations (2) to (4). The length of the resonance metal cavity in the first resonance mode is about 0.7 times the wavelength of the incident light (Equation 2), and the length of the resonance metal cavity in the second resonance mode is that of the incident light. It is about 1.54 times the wavelength (Equation 3). The length of the resonant metal cavity is about 1.8 times the wavelength of the incident light (equation 4), and the correlation coefficient R2 of each equation is more than 0.99.

In another embodiment of the present invention, the simulation of the localized surface plasmon resonance is carried out assuming a gold / p-type IPS structure and a silver / p-type IPS structure. The results are very close to the Cu-IPS structure described above. Therefore, it is confirmed that the key to the generation of localized surface plasmon resonance of the incident light in the IPS structure is the length of the plurality of cavities and the period of the structure. In order to induce high intensity localized surface plasmon resonance in the IPS structure, the period of the IPS structure is designed to be about 4 times the target resonance wavelength (IPS with a period of 4 nm corresponds to incident light of 1000 nm). Achieve the best light confinement effect and surface plasmon resonance intensity. Localized surface plasmon resonance structure of the length of a single resonance metal is designed with reference to the above equations (2) to (4), and the linear length and structure of the resonance metal required for the target wavelength are calculated. Thereby, a high-intensity localized surface plasmon resonance structure can be obtained.

FIG. 17 shows the double-sided polished p-type silicon substrate, copper / p-type silicon plane shotkey photodetector, copper / p-type silicon IPS shotkey photodetector, and gold / copper / p-type silicon plane shotkey photodetector. The absorption spectrum is illustrated. As shown in FIG. 17, the silicon substrate clearly has an absorption rate of about 60% to 70% in the visible light region before the cutoff wavelength of 1107 nm, and the absorption rate drops sharply in the vicinity of the cutoff wavelength. However, after the cutoff wavelength, the absorption rate becomes 0. Due to the increased reflectance of the copper film in the visible light region, the absorptivity of the copper / p-type photodetector in the visible light region is reduced by about 10% to 20% as compared to the silicon substrate. However, in the infrared region, the energy barrier of the shotkey junction is formed by the difference in the work functions of silicon and copper, the incident photons do not directly pass through the silicon, and a part of the incident light is the shotkey. The absorptivity of the photodetector, which is absorbed by the junction and is lower than the energy gap of silicon in the infrared region (λ> 1107 nm), increases to 40%, which is somewhat inadequate for the photodetector.

As shown in FIG. 17, when compared with the above two, the IPS structure has a three-dimensional dent effect due to the introduction of ultra-wideband LSPR, the active region of the surface nanostructure expands, and the absorption rate. Slightly improved. The copper / p-type silicon IPS photodetector has an absorption rate of more than 80% in the visible light region to the mid-infrared light region (450 nm to 2700 nm), and achieves an ultra-broadband absorption characteristic. The absorption spectrum is consistent with the simulation result and shows ultra-wideband resonance. The copper / p-type IPS structure has a gradually changing cavity length, the incident light having a wavelength of less than 4000 nm induces the localized surface plasmon resonance, and the photon confinement effect improves the light absorption efficiency. .. It has been repeatedly stated in Nature Communications that the copper / p-type IPS structure has a higher broadband resonance absorption rate than the 3D-DTTM structure (Lai, YS, Chen, HL, & Yu, CC). (2014). Silkon-based broadband antenna for high resonance and regeneration-incentive hoodometry at telecommunication wavelengths. Nature. (2014).

FIG. 18 illustrates plane and IV measurements of dark current with an IPS copper / p-type Schottky photodetector. As shown in FIG. 18, both the plane and the IPS photodetector exhibit the IV rectification characteristics of a general purpose Schottky diode, and when operating in the forward bias region, both photodetectors are PN. It has a small turn-on voltage compared to a junction diode. The turn-on voltage of the two photodetectors is about 0.1 V, and the dark current of the two photodetectors in the reverse bias region is very small. In the operating region of the two photodetectors, the dark current at 0 bias is about 1.66 μA. The difference between the dark currents of the two photodetectors is not clear when compared to the plane and the dark currents of the IPS photodetectors. It can be seen that the IPS structure on the surface of the photodetector does not alter the dark current performance of the copper / p-type silicon shotkey photodetector.

とほぼ一致している。前記入射光の波長が増すと、前記入射光子エネルギーが減少する。よって、前記平面光検出器の応答は前記長波長よりも前記短波長領域においてより明確になり、前記光検出器が−５ｍＶのバイアス電圧で動作する場合、前記光検出器の応答が３倍乃至１０倍向上する。この応答から分かるように、前記平面光検出器のカットオフ電圧は約２３５０ｎｍであり、ショットキー障壁の高さである約０．５３ｅＶに等しい。これは理論上算出される前記銅／ｐ型シリコンベースショットキーダイオードのショットキー障壁の高さと比較した場合である。前記（銅／ｐ型シリコン）接合は約０．５２ｅＶの高さのショットキー障壁を有し、本発明に係る前記銅／ｐ型シリコンベースショットキー光検出器が前記シリコンのバンドギャップより小さい光子エネルギーの光子を確実に計測可能であることを示す。然しながら、前記平面光検出器により前記光電流が生成されるメカニズムは、内部光電子放出吸収（ＩＰＡ）のみによるものであり、高効率の応答を達成することは容易ではない。 In one embodiment, the planar and IPS photodetectors are used to measure infrared light of different wavelengths (1150 nm to 2700 nm). The photodetector operates at 0 bias, the dark current and photocurrent are measured by a bias voltage of -5 mV, and how much overcurrent or how much is the photodetector when infrared light of various wavelengths is incident on the photodetector? It is calculated whether a response has occurred. FIG. 19 illustrates the plane and the response of the IPS photodetector as measured based on infrared light of different wavelengths. In the photodetector, when the photodetector operates with 0 bias, the response of the photodetector decreases as the wavelength of the incident light becomes longer. This trend is the formula of quantum conduction probability (η _i).

Is almost the same as. As the wavelength of the incident light increases, the incident photon energy decreases. Therefore, the response of the photodetector becomes clearer in the short wavelength region than in the long wavelength region, and when the photodetector operates at a bias voltage of -5 mV, the response of the photodetector is tripled or more. It improves by 10 times. As can be seen from this response, the cutoff voltage of the planar photodetector is about 2350 nm, which is equal to the height of the Schottky barrier, about 0.53 eV. This is the case when compared with the height of the Schottky barrier of the copper / p-type silicon-based Schottky diode calculated theoretically. The (copper / p-type silicon) junction has a Schottky barrier with a height of about 0.52 eV, and the copper / p-type silicon-based Schottky photodetector according to the present invention has a photon smaller than the bandgap of the silicon. It shows that the photon of energy can be measured reliably. However, the mechanism by which the photocurrent is generated by the planar photodetector is solely due to internal photoelectron emission absorption (IPA), and it is not easy to achieve a highly efficient response.

FIG. 19 shows that the IPS photodetector has an ultra-wideband and high intensity response, which is about 40 times that of the planar photodetector. Further, as the wavelength of the incident light increases, the response decreases, but it does not decrease as rapidly as the planar photodetector, and the cutoff wavelength of the IPS photodetector is not observed in the measurement wavelength range. Since the surface of the IPS photodetector has a surface plasmon resonance structure and a three-dimensional optical resonance cavity, the incident photons are effectively confined in the shotkey junction, which provides a strong proximity field and the metal. A large amount of hot carriers are generated in the semiconductor junction, and the response of the photodetector is effectively improved. Further, the IPS structure has a plurality of cavity lengths, and the simulation result shows that incident light having a wavelength of 500 nm to 4000 nm generates localized surface plasmon resonance in the IPS structure, and as the incident light wavelength increases. The resonance is amplified. As a result, not only is the response in a particular wavelength range improved, but a high response over ultra-wideband is also achieved, and the response is not as fast as the increase in incident wavelength. Furthermore, the measurement results also show that the IPS photodetector detected mid-infrared light with a lower energy than the Schottky barrier (in this case 0.53 eV: 2350 nm), which is the IPS photodetector. This is because it has an excellent localized surface plasmon resonance. The hot carriers excited by the incident of infrared light are stored in the metal because their energy is lower than the height of the Schottky barrier and cannot cross the energy barrier. However, a large amount of hot carriers excited by the localized surface plasmon resonance of the metal are accumulated in the metal-semiconductor junction. As shown in FIG. 20, when thermal equilibrium is reached after a large number of hot carriers collide with each other, some hot carriers acquire energy greater than the height of the Schottky barrier, and the hot air exceeds the energy barrier. Form a flow. As a result, the IPS photodetector not only improves the response to detect incident photons with energy lower than the silicon bandgap, but can also detect mid-infrared light with energy lower than the Schottky barrier.

FIG. 21 illustrates the photocurrent response of the IPS photodetector according to one embodiment of the invention, where the IPS photodetector has different incident light intensities (1.2 mW to 5.8 mW) and bias voltage. Working with a 1550 nm infrared laser with, the intensity of each incident light is measured three times. The current response of the photodetector to various incident light intensities is clearly different and gradually increases as the incident light intensity increases. The seven IV characteristic curves in FIG. 21 are measured at different incident light intensities, and for example, the dark currents are 1.2 mW, 2 mW, 3 mW, 4 mW, 5 mW, and 5.8 mW from top to bottom. .. The current response is proportional to the incident light intensity, indicating that the measured original current data is highly correlated with the incident light intensity.

FIG. 22 shows the relationship between the response and the incident light intensity when the IPS photodetector operates with a bias of 0 mV or -5 mV. When the IPS photodetector operates at 0 bias, the response of the photodetector is directly proportional to the intensity of the incident infrared light, and the measurement result is favorable linearity with a response of about 1032 nA / mW (R ² = 0. 997 high linearity). When the IPS photodetector operates with a bias of -5 mV, the photodetector response is directly proportional to the intensity of the incident infrared light and the measurement result is favorable linearity with a response of approximately 1343 nA / mW (R2 =). It exhibits a high linearity of 0.9864), which is about 30% higher than when operating at 0 bias. The photodetector according to the present invention provides a stronger responsiveness and a wider wideband absorption detection property than the conventional devices disclosed as described below. Deep groove / thin metal structure of 3D antenna by Mr. Knight et al. (Knight, MW, Sobhani, H., Nordlander, P., & Halas, NJ (2011). Photodetection with active antennas. -704) and Lin, Keng-Te et al. (Lai, YS, Chen, HL, & Yu, CC (2014) Silicon-based broadband antenna for high response resistance and polarization ).

FIG. 24 illustrates Schottky contacts made of silver nanofilms grown on a flat silicon substrate according to an embodiment of the invention. FIG. 25 illustrates a diagram showing the current response of FIG. 24, where the device operates at a wide range of voltages and zero biases, with light incident in the forward or reverse direction on the Schottky contact of the device. As shown in FIG. 25, the current response of the device is very stable when operating at 0 mV, and the response of the device to the incident light in the opposite direction is about twice that of the incident light in the forward direction. .. When the light is positively incident on the Schottky junction, the light passes through a thin film of the metal and is absorbed by the metal. Conversely, when the light is incident on the Schottky junction in the opposite direction, the light directly collides with the Schottky junction. Since the silicon substrate has a high absorption rate in the visible light region, the reverse incident method can be applied only to the detection of an infrared band.

As shown in FIGS. 24 and 25, when the light is changed to be incident on the Schottky junction in the opposite direction, the original silver Schottky contact nanofilm becomes thicker and changes from 10 nm to 100 nm. .. Thick Schottky contact remedies the drawback of the thin film layer being prone to oxidation.

FIG. 26 illustrates an upright pyramid structure (UPS) simulated by the finite element method and a change in which the light is incident on the Schottky contact from the silicon substrate. FIG. 27 shows an upright pyramid structure in which light having wavelengths of 1000 nm, 1500 nm, 2000 nm, 2500 nm, 3000 nm, 3500 nm, 4000 nm, 4500 nm, 5000 nm, 5500 nm, 6000 nm, 6500 nm, 7000 nm, 7500 nm, 8000 nm, 8500 nm, 9000 nm, 9500 nm, and 1000 nm is emitted. The simulation result in the case of vertically incident on each of the metal electrodes is shown. Cavities are formed between the upright pyramids. A strong light field confinement effect is observed in the Ag-UPS structure cavity for all incident wavelengths. This indicates that the structure is a preferred three-dimensional resonance cavity. When the incident wavelength changes, the surface plasmon resonance occurs in different regions of the cavity of the Ag-UPS structure. In the structure, the light enters the silicon substrate and the refractive index is increased, so that the wavelength of the incident light is attenuated, and the cavity for the same wavelength has a suitable linear length. Also, from all resonance simulations, the localized strong light field of the cavity of the Ag-UPS structure is reliably continuous from the strong proximity field of the metal, and the localized surface plasmon resonance (LSPR) clearly on the metal surface. It becomes clear that it causes. This demonstrates that the UPS structure has various or multiple cavity lengths and produces wideband localized surface plasmon resonance.

In one embodiment of the invention, a silicon-based Schottky photodetector is manufactured on a p-type silicon substrate using a metal-semiconductor junction (Cu—Si). An IPS (or UPS) structure is used to improve the response of the photodetector. The IPS structure has a one-dimensional mutant linear length, a two-dimensional symmetric periodic array, and a three-dimensional optical resonance cavity, which effectively enhances the light confinement effect and generates a photocurrent. From the results of simulations by the three-dimensional FDTD method and the finite element method, in the incident wavelength range of 500 nm to 4000 nm, a linear length suitable for the copper / p-type IPS structure exists to induce localized surface plasmon resonance. It can be seen that the copper / p-type IPS structure makes it possible to generate ultra-wideband localized surface plasmon resonance. In addition, the relationship between the wavelength of the incident electromagnetic wave and the linear length of the inverted pyramid structure is summarized. From the absorption spectrum, it can be seen that the copper / p-type silicon-based IPS photodetector has an ultra-wideband absorption rate of more than 80% for wavelengths in the range of 450 nm to 2700 nm. The conventional LSPR structure reliably solves the drawback that only surface plasmon resonance at the interband frequency can be induced. Response measurements of incident light of different wavelengths show that the copper / p-type IPS structure has favorable responsiveness for the incident wavelength in the range between 1150 nm and 2700 nm. When the device operates at 0 bias and 5 mV, the average response is 300 nA and 3500 nA, respectively, and the response does not drop sharply even if the incident light wavelength is increased. If the photodetector operates with a 1550 nm infrared laser at 0 bias, the response of the device will be up to 1032 nA / mW. Also, due to the preferred surface plasmon resonance effect of the copper / p-type IPS structure, the IPS structure not only improves the detection response of incident photons with energy lower than the energy gap of silicon, but also during incident with energy lower than the Schottky barrier. It also enables detection of infrared photons (2700 nm). The copper / p-type IPS structure also has the advantages of ultra-wideband absorption, polarization-independent resonance, and strong responsiveness. Further, the copper / p-type silicon IPS photodetector is manufactured through a silicon semiconductor process and a solution etching process. These processes are dead and stable technologies and can be carried out with inexpensive equipment and materials. Furthermore, the manufactured photodetector has high potential to be integrated into a silicon-based integrated circuit and developed into a silicon-based chip used in a visible infrared detector or a thermal infrared imaging device.

The above-described embodiment is merely for explaining the technical idea and features of the present invention, and an object of the present invention is to make a person familiar with the technical field understand the contents of the present invention and to implement the present invention. It does not limit the scope of claims. Therefore, various improvements or modifications having similar effects made without departing from the spirit of the present invention shall be included in the claims described below.

1 Optical detector 10 Semiconductor 12 ohm contact electrode 14 Metal electrode 141 Shotkey contact electrode 142 Grid electrode 2 Optical detector 20 Semiconductor 21 Silicon dioxide film 22 ohm contact electrode 23 Photoresist 24 Metal electrode 25 Chrome

Claims (8)

Having a first surface and a second surface, the second surface is opposite the first surface, and a semiconductor having a plurality of micro or nano-structures,
An ohmic contact electrode forming an ohmic contact with the first surface of the semiconductor,
A metal electrode with a Schottky contact with the second surface of the micro or nanostructure.
Each of the plurality of micro or nanostructures comprises a plurality of cavity linear lengths, with each wavelength in the wavelength range of incident light corresponding to one of the cavity linear lengths causing localized surface plasmon resonance (LSPR). Excited,
The carriers of the metal electrode are excited by the incident light to form electron-hole pairs or hot carriers, cross the shotkey barrier at the junction between the metal electrode and the semiconductor, and a photocurrent is formed to form the shotkey. It is characterized in that photons having an energy smaller than both the barrier and the band gap of the semiconductor are detected.
Photodetector. The photodetector according to claim 1, wherein the plurality of micro or nanostructures exhibit an inverted pyramid structure or an upright pyramid structure. The photodetector according to claim 1, wherein the incident light is incident from the first surface of the semiconductor. The photodetector according to claim 2, wherein in the inverted pyramid structure, localized surface plasmon resonance is excited by the wavelength of the incident light in the range of 500 nm to 4000 nm. The photodetector according to claim 2, wherein in the upright pyramid structure, localized surface plasmon resonance is excited by the wavelength of the incident light in the range of 1000 nm to 10000 nm. The photodetector according to claim 2, wherein the period of the inverted pyramid structure is four times the wavelength of the incident light. The photodetector according to claim 1, wherein the localized surface plasmon resonance is polarization-independent. The photodetector according to claim 2, wherein the absorption spectrum of the photodetector at a wavelength in the range of 450 nm to 2700 nm has an absorption rate of more than 80%.

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