Detection device having photodetector array

Abstract

A detection device includes a photodetector array composed of photodetectors, each of which includes a semiconductor layer, a metal layer in contact with the upper surface of the semiconductor, a first electrode in contact with the upper surface of the metal layer, and a second electrode in contact with the lower surface of the semiconductor layer. The photodetector reveals photoelectric and / or photothermal responses. As the energy of light source is insufficient to cross the Schottky energy barrier of the photodetector, the photodetector is locally thermal heated and reveals a photothermal response, which is converted into a square wave.

Description

Detection device with optical detection element array This invention relates to a detection device having an array of optical detection elements. Infrared light detection has numerous applications, including thermal imaging. Thermal imaging technology plays a crucial role in various fields, from night vision to medical diagnostics. Traditional thermal imagers typically use III-V semiconductor materials (such as InGaAs and HgCdTe) with excellent infrared light sensitivity and thermal noise characteristics as the substrate for sensors. However, these materials are expensive, complex to manufacture, and difficult to integrate in large-area arrays. The applicant's previous Republic of China patent application (application number 107116340) discloses a photodetector with a metal / semiconductor junction that uses a different mechanism to detect infrared light and has advantages such as ease of fabrication and low cost. Furthermore, previous research has fabricated different microstructure arrays on the surface of semiconductors, which can enhance the surface plasma effect and confine incident light deep within the microstructures. The gradient linewidth of the microstructures allows all wavelengths of incident light to generate a larger response signal through this mechanism. The applicant's previous Republic of China patent application (application number 11121205550) continued previous research by performing pre-processing and / or post-processing on the photodetector element, such as adding an insulating layer between the metal and the semiconductor to reduce noise and improve the signal-to-noise ratio (SNR). The resulting photodetector element has a response time of less than 10 microseconds. Some embodiments of the present invention provide a detection device having an array of photodetectors for detecting a light source. The array of photodetectors includes a plurality of photodetectors, each photodetector comprising a semiconductor layer; a metal layer, the lower surface of which forms a Schottky contact with the upper surface of the semiconductor layer; a first electrode in contact with the upper surface of the metal layer; and a second electrode in an ohmic contact with the lower surface of the semiconductor layer. The response signal of the photodetector includes a photoelectric response and / or a photothermal response. When the energy of the light source is insufficient to overcome the Schottky barrier of the photodetector, the photodetector is locally heated, resulting in the photothermal response. The array of photodetectors may have a processor to convert the photothermal response into a square wave signal. In one embodiment, the response signal of the photodetector is a square wave-like signal dominated by a fast photoelectric response. In another embodiment, the photothermal response is a triangular wave signal of response current changing over time, which is converted into a square wave signal of response current changing over time per unit time. In one embodiment, every N data points of the triangular wave signal are linearly regressed to obtain an instantaneous slope, and the obtained instantaneous slopes are plotted against time to obtain the square wave signal, from which a fast response slope is obtained. In one embodiment, the fast response slope is obtained by subtracting the different slopes of the square wave signal when it is on and off. In some embodiments, the detection device is a thermal imaging device, and its response signal may include photoelectric response and / or photoelectric response. The processor converts the photothermal response into a square wave signal to obtain a temperature signal, while the photoelectric response signal is a square wave signal and does not require further conversion. The semiconductor layer is preferably made of silicon. The wavelength range of the detected light source is between 2 μm and 15 μm. In some embodiments, the temperature of the detected light source is higher than the ambient temperature. The principle of array-type photodetectors is that mid-infrared incident light entering the Schottky junction is absorbed by the active layer of the element, exciting carriers that absorb the mid-infrared light. However, because the carrier energy is insufficient to cross the Schottky barrier, it cannot directly form a fast-responding light signal. The excited carriers then return to the ground state. During this return process, these excited electrons interact with surrounding atoms or molecules, causing changes in energy distribution. The purpose of detecting infrared light is achieved by detecting these energy changes. Advantages of the thermal imaging device in this invention: 1) Infrared light is detected by the energy change (photothermal response) of the detection element, thus achieving the ability to detect temperature changes. Furthermore, by using linear fitting to convert the slow triangular wave response into a fast square wave response, the temperature measurement results can be obtained in real time and accurately. 2) Silicon-based processes and low cost also facilitate integration with different silicon-based components. 3) It has a wide detection wavelength range (from visible light to mid-infrared light) and can measure temperatures from 35°C to several hundred degrees Celsius, giving it an advantage in thermal imagers. Thermal imagers made with silicon-based components have several advantages over other materials (such as indium arsenide (InAs) and mercury cadmium telluride (HgCdTe). First, silicon is one of the most mature materials in the semiconductor industry, with a complete manufacturing ecosystem (CMOS, MEMS processes). Compared to compound semiconductors like HgCdTe, silicon-based process technology is mature, production equipment is widespread, and costs can be effectively reduced. Furthermore, silicon-based thermal imaging components can be directly integrated with CMOS circuits to achieve single-chip solutions (SoCs). This integration improves image readout speed, reduces power consumption, and shrinks module size, enhancing industry compatibility. Silicon-based materials have good chemical stability and mechanical strength, making them suitable for long-term applications. Silicon also has a relatively low coefficient of thermal expansion, reducing the impact of thermal stress on component lifespan and providing higher reliability in harsh environments. Through mature CMOS processes, silicon-based thermal imaging technology can be used to produce large-area sensors, which is beneficial for manufacturing high-resolution thermal image sensing arrays. Traditional materials such as HgCdTe are difficult to maintain uniformity in large-area processes. In some embodiments, the detection device is used to detect one or more test gases. The detection device further includes a gas chamber in which the one or more test gases are disposed. After the light source passes through the one or more test gases, it is received by the photodetector array and converted into an electrical signal. The various embodiments of this invention will be described in detail below, with illustrations provided. In addition to these detailed descriptions, the invention can be widely implemented in other embodiments, and any easy substitutions, modifications, or equivalent changes to these embodiments are included within the scope of this invention and are subject to the following patent claims. In the description of the specification, many specific details are provided to give the reader a more complete understanding of the invention; however, the invention may still be implemented with some or all of these specific details omitted. Furthermore, well-known procedural steps or elements are not described in the details to avoid unnecessarily limiting the invention. In various embodiments of the Republic of China Patent (Application No. 107116340), photodetectors with planar silicon surfaces and silicon surfaces having inverted pyramid arrays have been fabricated. The entire contents of the aforementioned patent are incorporated herein by reference and are considered part of this application. Some embodiments of the present invention provide a detection device with a photodetector array, wherein the photodetector array comprises a plurality of photodetectors. Each photodetector may be a photodetector with a planar silicon surface and a silicon surface having a microstructure array (containing one or more microstructures, such as an inverted pyramid array containing one or more inverted pyramids), comprising a semiconductor layer, a metal layer, a first electrode, and a second electrode. The lower surface of the metal layer forms a Schottky contact with the upper surface of the semiconductor layer. The first electrode is in contact with the upper surface of the metal layer. The second electrode forms an ohmic contact with the lower surface of the semiconductor layer. The response signal of the photodetector may include a photoelectric response and a photothermal response. When the energy of the light source is insufficient to overcome the Schottky barrier of the photodetector, the photodetector is locally heated, thereby generating the photothermal response. Using infrared spectroscopy, this photodetector array can be used for gas detection (including VOCs respirator analysis and environmental gas analysis in medicine), blood glucose measurement, and food composition analysis. The photodetector array can also be applied to thermal imaging. The light source detected by the photodetector array can be light emitted by the object being tested, or it can be transmitted or reflected light illuminating the object with infrared light. A beam-splitting device can be present between the light source and the object being tested, such as, but not limited to, one or more gratings, mirrors, filters, and / or lenses, to separate the light source and focus the different wavelengths of the separated light source onto one or more corresponding photodetector elements of the photodetector array. The photodetector array can also detect multiple light sources simultaneously. For ease of explanation, the following embodiments illustrate that the photodetector array provided by the present invention can be applied to a thermal imaging device, but is not limited thereto. As shown in Figure 1, one embodiment of the present invention provides a thermal imaging device comprising a photodetector array 1 for detecting infrared radiation emitted by an object 2 (including a human body, animal, or object). An optical path device 3 for filtering and / or focusing may be provided between the object 2 and the photodetector array 1. Additionally, the thermal imaging device may have a back-end integration module 4 connected to the photodetector array 1 to process the detected signals. In some embodiments, each photodetector element 10 in the photodetector element array 1 is a planar photodetector element as shown in FIG2A, which includes a semiconductor layer 103, a metal layer 104, a first electrode 101, and a second electrode 102. The lower surface of the metal layer 104 forms a Schottky contact with the upper surface of the semiconductor layer 103. The first electrode 101 is in contact with the upper surface of the metal layer 104. The second electrode 102 forms an ohmic contact with the lower surface of the semiconductor layer 103. In other embodiments, each photodetector 10 in the photodetector array 1 is a photodetector 10 having an inverted pyramid array (containing one or more inverted pyramids) on the surface of the semiconductor layer 103 as shown in FIG2B. In a preferred embodiment, the semiconductor layer 103 in Figures 2A and 2B is an n-type silicon substrate, the metal layer 104 is silver, the first electrode (finger electrode) 101 is silver, and the second electrode 102 is aluminum. The following describes examples of fabrication of a planar photodetector 10 or an inverted pyramidal photodetector 10. A double-polished N-type silicon substrate with a thickness of 600-610 μm and a resistance of 2-7 Ω·cm was used. Using a diamond cutter and tweezers, the silicon substrate was cut into squares approximately 2.5cm × 2.5cm in size. The silicon substrate was then ultrasonically cleaned sequentially with acetone, isopropanol (IPA), and deionized water (DI water), each step lasting approximately 10 minutes. SiO₂ with a thickness of approximately 600 nm was grown on a silicon substrate using plasma chemical vapor deposition (PECVD). Two layers. HMDS was spin-coated using a spin coater, with an initial spin speed of 1000 rpm for 10 seconds, followed by a final spin speed of 4000 rpm for 40 seconds. ENPI-307 negative photoresist was then spin-coated using the same spin coater, with an initial spin speed of 1000 rpm for 10 seconds, followed by a final spin speed of 4000 rpm for 40 seconds. When spin-coating the negative photoresist, the photoresist was dropped onto the substrate and allowed to stand for 5-10 seconds to allow for full coverage. The spin-coated substrate was then placed on a heated platform and softened at 110°C for 3 minutes. Expose and develop the substrate: Expose the substrate for 20 seconds using an exposure machine, then bake at 130°C for 2 minutes. Develop using MF-319 developer (approximately 40 seconds), and check the pattern using an optical microscope. After confirmation, bake at 130°C for 3 minutes. Dry etching was performed using reactive ion etching (RIE) with the following parameters: etching SiO 2, CHF 3:30 sccm, pressure: 1.3 Pa, RF power: 90 W, duration: 30 minutes. Photoresist etching (PR), O 2: 50 sccm, pressure: 13.3 Pa, RF power: 100W, duration: 25 minutes. To fabricate an inverted pyramid array on a silicon substrate, a wet etching method is used: Heat the KOH solution to 75 degrees Celsius using a heated stage (temperature between 150 and 180 degrees Celsius); immerse the substrate in the KOH solution for approximately 15 minutes (starting with 10 minutes is recommended, but longer may be required), then remove and rinse with purified water, and dry. Observe the etching results using an optical microscope. Alternatively, immerse the substrate in a buffered oxide etchant (BOE) solution for five minutes to remove surface silicon dioxide (SiO₂). 2) Then clean with purified water. A uniform aluminum metal layer with a thickness of 100 nm was deposited on one side of the substrate using a thermal evaporation machine as the back electrode, with a deposition rate of 1 Å / s. A 10 nm layer of silver metal was deposited on the other side of the substrate using a thermal evaporation machine. This silver metal layer will serve as the active layer for photosensitive functions in the device. The evaporation rate was 0.1 Å / s. Finally, silver finger electrodes with a total thickness of 100 nm were continuously deposited on the active layer at deposition rates of 0.1 Å / s (10 nm), 0.3 Å / s (10 nm), 0.5 Å / s (10 nm), and 1 Å / s (10 nm). If rapid thermal annealing is required, place the plated components in a rapid thermal annealing machine and perform rapid thermal annealing according to the specific parameters required. Figure 3 shows the measurement architecture used in the experiments of this invention. Referring to Figure 3, the measurement architecture includes a light source 30, a chopper 31, a device under test (DUT) 32, a multifunction power meter 33 (Keithley 2400), and a computer 34. The DUT 32 is the photodetector 10 shown in Figure 2A or Figure 2B. Depending on the test temperature, the light source 30 can be a ceramic heating element that is electrically heated to produce blackbody radiation. A thermocouple 35 can be used to detect the temperature of the light source 30. In some experiments, the light source 30 is a thermoelectric cooler connected to a temperature controller (not shown) to control the output of low-temperature blackbody radiation from the thermoelectric cooler. The chopper 31 can have fixed on and off times, for example, 5-10 seconds on and 5-10 seconds off, to generate an ON-OFF period of 10-20 seconds. Figure 3 shows a vertical measurement architecture. Part of the experiments of this invention are conducted in a horizontal measurement architecture, that is, the light source 30 and the device under test (DUT) 32 are at the same horizontal height. Furthermore, a reflective tube 36 may be provided between the chopper 31 and the light source 30, depending on the requirements. Additionally, a reflector may be placed behind the light source 30, depending on the requirements, to enhance the light intensity. Furthermore, a single-spectrum may be provided between the chopper 31 and the DUT 32 to split the light from the light source before it enters the DUT. The distance between the DUT 32 and the light source 30 is 2-10 cm. The electrical signal generated by the DUT 32 after receiving the light is received by a multi-function power meter 33 (Keithley 2400) and then transmitted to a computer 34 for processing. The measurement architecture is typically covered by a box to prevent light leakage. Under a horizontal measurement framework, a planar photodetector with a 0.1-volt bias was measured using a 200-degree blackbody radiation source. The response was observed to be a square wave signal, with the top and bottom of the square wave signal showing an increase or decrease over time. In fact, when a photodetector receives light, it generates two response signals simultaneously. Wen et al. [46-47] categorized these response signals into photoelectric (PE) and photothermal (PT) responses. The former is the rapid current response generated by the element when illuminated at the moment of switching. The latter is the current signal that changes over time when the element is continuously illuminated or not. Experiments showed that the photodetector fabricated in this application also exhibits both fast and slow responses under a bias voltage. Under positive bias, the PT photothermal response and PE photoelectric response are opposite in direction, but their response times differ. This results in the observation of a momentary switching PE photoelectric response signal, which is linear, while the PT photothermal response signal requires time to accumulate before a larger response current value appears. Table 1 shows the response signals of a planar photodetector element at different light source temperatures under different bias voltages (0.1, 0.2, and 0.3 volts). As observed in Table 1, at a bias voltage of 0.1 volts and a light source temperature of 200 degrees Celsius, the fast response is very pronounced, with only slight tilts at the top and bottom of the square wave, exhibiting a low slope. When the light source temperature drops to 150 degrees Celsius, the proportion of the fast response decreases significantly, the tilt at the top and bottom of the square wave increases sharply, and the slow response becomes more prominent than the fast response. When the light source temperature drops to 100 degrees Celsius, the fast square wave response completely disappears, replaced by a complete slope change, presenting a triangular wave signal. This indicates that as the temperature of the light source decreases, the photoelectric (PE) response signal gradually decreases, and the photothermal (PT) response becomes dominant. This change was also observed when a bias voltage of 0.2 or 0.3 volts was applied. Table 1 As observed in Table 1, when the light source temperature is fixed at 200 degrees Celsius, a fast-response square wave signal is evident at a bias voltage of 0.1 volts. As the bias voltage increases to 0.2 volts, the proportion of the slow response increases. When the bias voltage increases to 0.3 volts, the proportions of the slow and fast responses are approximately equal. This situation is similar to that of temperature changes, but the cause is different. At the same bias voltage, the difference between the highest and lowest points of the response current gradually decreases as the light source temperature decreases, meaning that the photoelectric response decreases with decreasing light source temperature. This indicates that the number of thermal carriers directly crossing the energy barrier is reduced due to photon energy excitation from blackbody radiation. As the light source temperature gradually decreases, only the slow-response signal remains. The above experimental results can be explained as follows: When a reverse bias is applied to the device, the dark current is small, and its impact on the current response is minimal. However, when a forward bias is applied, a conduction current is generated, and the device is affected by local heating effects, causing changes in its electrical properties, such as series resistance and the Schottky barrier, resulting in a triangular wave-shaped photothermal response. Applying a forward bias to the device leads to an increase in the photothermal response, while a decrease in the light intensity as the light source temperature decreases leads to a reduction in the photoelectric response of the device, ultimately leaving only the photothermal response as the dominant factor. The hot carriers generated after the metal surface receives light are thermally diffused to the Schottky interface. Carriers that fail to cross the barrier accumulate in the metal region and heat the interface, causing changes in the interface's electrical properties and generating a photothermal (PT) response current under an applied bias, the direction of which is always the same as the applied bias direction. Next, the voltage-current curves of the planar photodetector were measured at different temperatures, and these curves were fitted using the thermionic emission formula. The results are summarized in Table 2. Table 2 As shown in Table 2, the series resistance and barrier height of the component increase and decrease respectively as the temperature increases. In a horizontal measurement architecture, the photodetector is only affected by thermal radiation. However, in a vertical measurement architecture, in addition to thermal radiation, there is also thermal convection, which may lead to a more pronounced localized heating effect on the photodetector. Tests were conducted at different light source temperatures using a planar photodetector with a 0.1V bias applied to it under a horizontal measurement architecture. The results showed that the photoelectric response remained relatively clear at a light source temperature of 200°C. Even at 150°C, while noise increased, the response signal was still clearly identifiable. However, when the light source temperature dropped to 135°C, the response signal became less pronounced and gradually became indistinguishable, eventually becoming unobservable at 120°C. Based on the results of the horizontal measurement architecture, the measurement cutoff temperature of the planar photodetector is approximately 135°C. On the other hand, the same experiment was conducted under a vertical measurement architecture. The results showed that the photoelectric response remained relatively clear at a light source temperature of 150°C, and noise was reduced compared to the horizontal architecture. Furthermore, the response signal was still clearly observable at a light source temperature of 100°C, and even a weak signal was observed at 50°C. Compared to the horizontal measurement architecture, the vertical architecture significantly improved the measurement sensitivity and cutoff temperature. Table 3 shows the response current of the planar photodetector at different light source temperatures under a 0.3V bias voltage (measured using a vertical measurement architecture). As the light source temperature decreases, the response current also decreases; a distinct triangular wave signal can still be observed at 100°C and 50°C. Further, in 10-degree increments, a relatively noticeable response can be observed between 40°C and 30°C. No signal is generated only after the light source power is turned off and the light source has completely cooled to room temperature. Table 3 Table 4 shows the response current of the inverted pyramid photodetector at different light source temperatures under a 0.3V bias voltage (measured using a vertical measurement architecture). As shown in Table 4, a distinct triangular wave signal can be observed at both 100° and 50° light source temperatures. Further, in 10-degree increments, noise gradually becomes more noticeable between 40° and 30°, but a distinct triangular wave signal is still visible. No signal is generated only after the light source power is turned off and allowed to cool completely to room temperature. Compared to planar sensors, the inverted pyramid sensor exhibits significantly more noise in its measurements. Table 4 Following Tables 3 and 4, a 0.3V bias voltage was applied to both planar and inverted pyramidal photodetector elements, and measurements were taken in 2-degree increments between 40 and 30 degrees Celsius. Temperature changes were clearly observed. As the temperature decreased, the response current also decreased accordingly. Although a 2°C temperature change could be detected, significant noise affected the resolution of the temperature detection. Furthermore, the response current was affected by the chopper's switching cycle. Therefore, this problem was addressed by analyzing the instantaneous slope change of the triangular wave. The slope analysis method is unaffected by the switching cycle. This method extracts the slope of the original data point and several neighboring points, then averages these slopes and converts them into a new signal. As shown in Figure 4, the slow-response triangular wave on the left is converted into a fast-response square wave on the right. Through this slope analysis method, a more stable signal unaffected by the switching time can be obtained, thereby improving the resolution of temperature changes. In a preferred embodiment, a linear regression method is used for signal transformation. The goal is to find the linear regression slope as the signal rises or falls by taking different numbers (e.g., 10, 20, 30, 40, 50) of data points from the triangular wave data, minimizing the sum of squared residuals between the observed values ​​and the line. These slopes are found using the least squares method. Before transformation, the response current is plotted against time; after transformation, the linear regression slope (response current per unit time) is plotted against time. Assume the linear regression model is as follows: in, It is the dependent variable. It is the independent variable. It is the intercept. It's the slope. This is the error term. The goal is to find the solution that minimizes the sum of squared residuals. and Define residuals For observations Compared with the predicted value The difference between them: Predicted value It can be obtained through the regression equation: The objective is to minimize the sum of squared residuals for all observations, i.e.: Minimize Will Substituting and expanding, we get: Now, we need to find the expression that minimizes this expression. and . In order to find and We need to minimize this expression, by doing the following: and Find the derivative and set it equal to zero. right Find the derivative: right Find the derivative: Solving these two equations will yield the result that minimizes the sum of squared differences. and . Pick Using the slope value as a guide, all data points of the triangular wave signal are converted into linear regression slopes and plotted against time. Table 5 shows the average slope of different numbers of data points (10 / 20 / 30 / 40 / 50) using an inverted pyramid (IPS) photodetector with a fixed light source temperature of 30 degrees and an applied bias voltage of 0.3V. Table 5 As shown in Table 5, with the increase of the number of sampling points, the noise in the converted signal decreases, and the signal becomes more distinct. When the number of sampling points reaches 50, the converted signal becomes recognizable. The number of sampling points is not limited to those mentioned above. Figure 5 shows a bar graph illustrating the measurement process using a vertical measurement architecture. The pyramid-shaped photodetector element measures in 1-degree increments within a 30-40 degree range, and 50 data points are collected to convert the measured triangular wave signal into a square wave signal. The response magnitude is obtained by subtracting the average slopes of the square wave signal when it is on and off in this bar graph. It is clearly observed from the graph that the response current increases with increasing light source temperature. Furthermore, using a vertical measurement architecture, the raw data (response current) of pyramid-shaped and planar photodetectors were compared under different light source temperatures, with or without a bias voltage of 0.1V. Experimental results showed that at the same light source temperature, the response current of the inverted pyramid-shaped element was significantly larger, and this was even more pronounced after applying a bias voltage of 0.1V. At a light source temperature of 50 degrees Celsius without bias, the planar element could no longer measure a signal, while the inverted pyramid element still allowed for signal changes to be observed. Simultaneously, the inverted pyramid-shaped element was more susceptible to localized heating effects. Figure 6 shows a bar graph illustrating the results of a vertical measurement architecture using both pyramidal photodetectors (IPS) and planar photodetectors. A bias voltage of 0.1V was applied, and measurements were taken in 1-degree increments within a 30-40 degree range. Fifty data points were collected, and the measured triangular wave signal (slow response) was converted into a square wave signal (fast response). As shown in Figure 6, converting the slow response to a fast response allows for effective data comparison. The response current of both photodetectors increases with increasing light source temperature, but the inverted pyramidal photodetector provides a larger response. Minimum temperature change sensitivity confirmation Figures 7A and 7B show the raw data obtained by using a vertical measurement architecture, a planar photodetector element, the element being 2 cm away from the light source, a bias voltage of 0.1V applied, and a chopper that is turned on and off for 10 seconds at a time, within the range of 35 to 42 degrees, with a step size of 0.2 degrees. Figures 8A and 8B show the fast response of converting the measured triangular wave signal into a square wave signal by taking 50 data points from the slow response in the original data of Figures 7A and 7B. Figure 9 shows a vertical measurement architecture using a planar photodetector element. The element is 2 cm away from the light source, and a bias voltage of 0.1V is applied. Measurements are performed in 0.2-degree increments within the range of 35 to 42 degrees. A bar graph of the slope of the response value after converting the measured triangular wave signal into a square wave signal is obtained by taking 50 data points. The slope of the response value is obtained by subtracting the different slopes of the square wave signal when it is on and off. As shown in Figure 9, the slope of the response current of the planar element decreases as the temperature of the light source decreases. This proves that the planar element has a measurement accuracy of 0.2℃ and can effectively distinguish changes in temperature as small as 0.2℃. Figures 10A and 10B show the raw data obtained by using a vertical measurement architecture with an inverted pyramid-shaped photodetector element. The element is 2 cm away from the light source, a bias voltage of 0.1V is applied, and the chopper is turned on and off for 10 seconds. The measurement is performed in 0.2-degree increments within the range of 35 to 42 degrees. Figures 11A and 11B show the fast response of converting the slow response in the original data of Figures 10A and 10B into a square wave signal. Figure 12 shows a vertical measurement architecture using an inverted pyramid-shaped photodetector element. The element is 2 cm away from the light source, and a bias voltage of 0.1V is applied. Measurements are performed in 0.2-degree increments within the range of 35 to 42 degrees. A bar graph of the slope of the response value after converting the measured triangular wave signal into a square wave signal is obtained by taking 50 data points. The slope of the response value is obtained by subtracting the different slopes of the square wave signal when it is on and off. As shown in Figure 12, the slope of the response current of the inverted pyramid-shaped element decreases as the temperature of the light source decreases. This demonstrates that the inverted pyramid-shaped element has a measurement accuracy of 0.2℃ and can effectively resolve temperature changes as small as 0.2℃. Next, the measurement data of the planar and inverted pyramidal components were presented as scatter plots, and linear fitting was performed using a two-variable linear equation, as shown in Figure 13. The R-squared (also known as the coefficient of determination) of the linear regression analysis for both the planar and inverted pyramidal components is very close to 1. Through linear fitting, the response current at higher or lower light source temperatures can be predicted. Notably, the slope of the linear fitting for the inverted pyramidal component is greater than that for the planar component. Figures 17A and 17B show the raw data obtained by using a vertical measurement architecture with an inverted pyramid-shaped photodetector (period 14μm), the element being 2 cm away from the light source, a bias voltage of -0.3V applied, and a chopper that is on for 10 seconds and off for 10 seconds. The measurement is performed in 0.1 degree increments within the range of 35 to 42 degrees. Figures 18A and 18B show the slow responses from the original data in Figures 17A and 17B, processed using the aforementioned linear regression method. This is converted into a fast response of a square wave signal. Figure 19 is a line graph of the fast response (response current slope) versus temperature in Figure 18. Figures 17A / B to 19 and other experimental results show that the measurement accuracy can reach 0.1 degrees Celsius when a negative bias voltage is applied to the photodetector. Furthermore, the response current of the photodetector when a negative bias voltage is applied is greater than the response current of the photodetector when a positive bias voltage is applied. The above series of experimental results demonstrate that the planar and inverted pyramidal photodetector elements of this invention can be applied to low-temperature measurements, such as body temperature and blackbody radiation, and possess excellent detection sensitivity and accuracy. By converting a slow response into a fast response, the comparability and accuracy of the data are improved. Furthermore, the fabricated planar and inverted pyramidal photodetector elements can measure the mid-infrared light band with a cutoff wavelength of 7 micrometers, making them excellent infrared photodetector elements applicable to many fields, such as environmental monitoring, night vision technology, medical diagnostics, and security systems. The following embodiments illustrate that the photodetector array provided by the present invention can be applied to gas detection, but is not limited thereto. Figures 14A to 14D show a detection device with a photodetector array for detecting gases according to some embodiments of the present invention. Referring to Figures 14A to 14D, the light source 30 is used to provide a stable broadband radiation source (wavelength range from near-infrared (NIR) to mid-infrared (MWIR)) to accommodate the absorption characteristics of different gases. The light emitted by the light source 30 is accurately guided to the detection area where the gas to be measured is located by one or more reflectors / lenses 6 (reflectors and / or lenses). This optical path design ensures uniform light distribution, extends the optical path, and maximizes signal sensitivity. The light passes through one or more gases to be measured disposed in a sealed gas chamber 40, the walls of which may be transparent or at least partially reflective. The molecules of the gas to be measured will produce absorption or scattering effects on light of a specific wavelength, and this effect is the basis of detection. A filter array 5 is disposed behind the gas chamber 40. This filter array separates the light source 30 into beams of different wavelengths, which then illuminate one or more corresponding photodetector elements 10 in the photodetector element array 1. The filter array 5 can filter based on the characteristic absorption wavelengths of the target gas to improve detection accuracy. The photodetector element array 1 converts the light into electrical signals using photodetector elements 10 corresponding to each wavelength, thereby detecting the concentration or composition of the gas to be measured. In this embodiment, the detection device can be an integrated chip. Figure 15 shows a detection device with an array of photodetectors for detecting gases according to another embodiment of the present invention. A light source 30 provides a stable broadband radiation source (wavelength range from NIR to MWIR), suitable for analyzing various analyte gases. The broadband light emitted by the light source 30 is separated into multiple monochromatic beams by a beam splitter 7 (such as a grating or prism). The beam splitter 7 can accurately divide the light source 30 into the desired wavelength range, providing a basis for subsequent detection. One or more analyte gases are disposed in a sealed gas chamber 40, and the separated beams interact with the analyte gases. The gases selectively absorb light of specific wavelengths, the degree of absorption reflecting the composition and concentration of the analyte gas. The beams of different wavelengths, separated by the beam splitter 7, illuminate one or more corresponding photodetectors 10 in the photodetector array 1, which convert the corresponding beams into electrical signals. These electrical signals can be used to calculate the absorption spectrum of the analyte gas. In this embodiment, the detection device can be an integrated chip. Figure 16 shows a detection device with an array of photodetectors for detecting gases according to another embodiment of the present invention. In this embodiment, the detection device can be a multifunctional integrated chip. Referring to Figure 16, the detection device includes a light source 30, an array of photodetectors 1, multiple waveguide optical channels 41, an electrical amplifier 42, and a gas chamber 40 for accommodating one or more gases to be tested. The light source 30 is an array light source, which includes multiple narrow-band light sources (301, 302, 303...) to emit monochromatic light beams of different wavelengths to irradiate one or more gases to be tested. The gases to be tested absorb light of a specific wavelength, and the transmitted or reflected light passes through the corresponding waveguide optical channels 41 and illuminates one or more photodetectors 10 in the photodetector array 1. In some embodiments, the waveguide optical channels 41 may not be required. In some embodiments, the number of gases to be tested is multiple, and the wavelengths of the monochromatic light beams each correspond to one gas to be tested. In some embodiments, symbol 41 represents not a waveguide optical channel, but an independent gas channel, in which one or more identical target gases are contained within each gas channel. The gas channels can be interconnected, but the optical paths do not interfere with each other. Monochromatic beams emitted by multiple narrow-band light sources (301, 302, 303…) pass through a gas channel and are converted into electrical signals by one or more corresponding photodetector elements 10 in the photodetector array 1. The detection device may also have an electrical amplifier 42. The photodetector array 1 is connected to the electrical amplifier 42, which includes an electronic circuit signal processor and communication circuits, etc. In this embodiment, the sensor front-end (sensor element technology), back-end (electronic circuit signal processor, communication technology), power supply, and communication are integrated onto a single chip using complementary metal-oxide-semiconductor (CMOS) technology, achieving a multi-functional integrated chip. Some of the experimental content cited in this invention is taken from the master's thesis of Chen Yilong, Institute of Optoelectronic Engineering, College of Electrical and Computer Science, National Taiwan University, entitled "Study on the Mid-Infrared Photoelectric Properties of Silicon-Based Schottky Detectors and the Influence of Metal Thin Film Morphology on Them". More experimental content can be found in the aforementioned thesis, the entire contents of which are incorporated herein by reference and considered part of this specification. The photodetector element in the above embodiments uses specific materials, but other materials, such as those described in TW patent applications 107116340 and 110145523, may also be used in other embodiments. For example, the metal layer may comprise gold, silver, copper, chromium, nickel, or combinations thereof. The above embodiments of the present invention are merely for illustrating the technical ideas and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the patent scope of the present invention. All other equivalent changes or modifications made without departing from the spirit disclosed in the present invention are covered within the scope disclosed in the present invention and should be included in the patent application scope below. 1: Photodetector array 2: Object 3: Optical path device 4: Back-end integrated module 5: Filter array 6: Mirror / lens 7: Beam splitter 10: Photodetector 101: First electrode 102: Second electrode 103: Semiconductor layer 104: Metal layer 30: Light source 31: Chopper 32: Component under test 33: Multifunction power meter 34: Computer 35: Thermocouple 36: Reflector tube 40: Gas cell 41: Waveguide optical channel 42: Electrical amplifier Figure 1 shows the photodetector element of a thermal imaging apparatus according to an embodiment of the present invention. Figure 2A shows the photodetector element of a thermal imaging apparatus according to an embodiment of the present invention. Figure 2B shows the photodetector element of a thermal imaging apparatus according to an embodiment of the present invention. Figure 3 shows the measurement architecture used in the experiments of this invention. Figure 4 shows the conversion of a triangular wave signal from a photodetector into a square wave signal according to an embodiment of the present invention. Figure 5 is a bar graph showing the response current of a pyramid-shaped photodetector after converting triangular wave signals into square wave signals at 1-degree intervals within a temperature range of 30 to 40 degrees Celsius. Figure 6 is a bar graph comparing the response currents of pyramid-type and planar-type photodetectors after the triangular wave signals are converted into square wave signals at 1-degree intervals within a temperature range of 30 to 40 degrees Celsius. Figures 7A and 7B show the triangular wave signals of a planar photodetector element at 0.2-degree intervals within a temperature range of 35 to 42 degrees Celsius. Figures 8A and 8B show the square wave signals generated by the planar photodetector at 0.2-degree intervals within a temperature range of 35 to 42 degrees Celsius. Figure 9 is a bar graph showing the slope of the response values ​​of a planar optical detection element for square wave signals spaced 0.2 degrees apart within a temperature range of 35 to 42 degrees Celsius. Figures 10A and 10B show the triangular wave signals of the inverted pyramid-shaped photodetector at 0.2-degree intervals within the temperature range of 35 to 42 degrees Celsius. Figures 11A and 11B show the square wave signals generated by the inverted pyramid-shaped photodetector at 0.2-degree intervals within a temperature range of 35 to 42 degrees Celsius. Figure 12 is a bar graph showing the slope of the response values ​​of a square wave signal at 0.2-degree intervals within the temperature range of 35 to 42 degrees Celsius for an inverted pyramid-shaped photodetector. Figure 13 shows the scatter plot and linear fit of the response values ​​of the planar photodetector and the inverted pyramid photodetector at 0.2-degree intervals within the range of 35 degrees to 42 degrees for square wave signals. Figures 14A to 14D show detection devices with an array of photodetector elements for detecting gases according to some embodiments of the present invention. Figure 15 shows a detection device with an array of photodetectors for detecting gases according to another embodiment of the present invention. Figure 16 shows a detection device with an array of photodetectors for detecting gases according to another embodiment of the present invention. Figures 17A and 17B show triangular wave signals generated by an inverted pyramid-shaped photodetector with a negative bias applied at 0.1-degree intervals within a temperature range of 35 to 42 degrees Celsius. Figures 18A and 18B show the square wave signals generated after the inverted pyramid-shaped photodetector is subjected to a negative bias voltage and the temperature is converted at 0.1-degree intervals within the range of 35 to 42 degrees Celsius. Figure 19 is a line graph showing the response current versus temperature for the square wave signals in Figures 18A and 18B. 1: Optical Detection Element Array 2:Object 3: Optical path device 4: Backend Integration Module 10: Photodetector

Claims

1. A detection device for detecting a light source includes: an array of photodetectors comprising a plurality of photodetectors, each photodetector comprising: a semiconductor layer; a metal layer, the lower surface of the metal layer forming a Schottky contact with the upper surface of the semiconductor layer; a first electrode in contact with the upper surface of the metal layer; and a second electrode in an ohmic contact with the lower surface of the semiconductor layer; wherein... The response signal of the photodetector includes photoelectric response and / or photothermal response. When the energy of the light source is insufficient to overcome the Schottky barrier of the photodetector, the photodetector is locally heated, resulting in the photothermal response. The photodetector array further includes a processor to convert the photothermal response into a square wave signal. The detection device of claim 1, wherein the response signal of the photodetector is a square wave-like signal, and the response signal of the photodetector when a negative bias voltage is applied is greater than the response signal of the photodetector when a positive bias voltage is applied. The detection device of claim 1, wherein the photothermal response is a triangular wave signal of response current changing with time, and the triangular wave signal is converted into a square wave signal of response current slope changing with time per unit time. The detection device of claim 3, wherein every N data points of the triangular wave signal are linearly regressed to obtain an instantaneous slope, the obtained instantaneous slopes are plotted against time to obtain the square wave signal, and a fast response slope is obtained based on the square wave signal. The detection device, as in claim 4, wherein the fast response slope is obtained by subtracting the different slopes of the square wave signal when it is on and off. The detection device of claim 1, wherein the detection device is a thermal imaging device, the response signal of which includes photoelectric response and / or photothermal response, the photoelectric response being a square wave signal of response current changing with time, the photothermal response being a triangular wave signal of response current changing with time, the triangular wave signal being converted into a square wave signal of response current slope changing with time per unit time, and the square wave signal being converted into a temperature signal. The detection device of claim 6, wherein every N data points of the triangular wave signal are linearly regressed to obtain an instantaneous slope, the obtained instantaneous slopes are plotted against time to obtain the square wave signal, and a fast response slope is obtained based on the square wave signal. The detection device of request item 7, wherein the fast response slope is obtained by subtracting the different slopes of the square wave signal when it is on and off. The detection device, as in claim 7, wherein the photothermal response is converted into a temperature signal according to a detection line. The detection device of claim 9, wherein within a temperature range of 35˚C to 42˚C, acquires triangular wave signals from the photodetector at 0.2˚C intervals and converts them into square wave signals respectively, and obtains the fast response slope from the converted square wave signals, and plots the acquired fast response slopes against the light source temperature to obtain the detection curve. The detection device of claim 6, wherein the wavelength range of the light source is between 2μm and 15μm. The detection device, as in claim 6, has a light source with a temperature higher than the ambient temperature. The detection device, as in claim 6, wherein the temperature of the light source is between 30˚C and 200˚C. The detection device of claim 6, wherein the surface of the semiconductor layer has an array of inverted pyramid structures. The detection device of claim 6, wherein the semiconductor layer is made of silicon, and the metal layer is made of gold, silver, copper, chromium, nickel, or a combination thereof. The detection device of claim 1, wherein the detection device is used to detect one or more test gases, the detection device further includes a gas chamber in which the one or more test gases are disposed, and the light source passes through the one or more test gases and is converted into an electrical signal by the photodetector array. The detection device of claim 16, wherein the light source is a light source with wavelengths covering near-infrared (NIR) to mid-infrared (MWIR), the detection device further includes one or more reflective / lenses and a filter array, the light source being converted into an electrical signal by the light detection element array after passing through the one or more reflective / lenses disposed in the air chamber and then through the filter array. The detection device of claim 16, wherein the light source is a light source with wavelengths covering near-infrared (NIR) to mid-infrared (MWIR), the detection device further includes a beam splitter, and the light source is converted into an electrical signal by the light detection element array after passing through the beam splitter disposed in the air chamber. The detection device of claim 16, wherein the light source includes a plurality of narrowband light sources to emit monochromatic beams of different wavelengths, the monochromatic beams passing through the one or more gases to be measured are received by the photodetector array and converted into electrical signals. The detection device of claim 19, wherein the gas chamber contains a plurality of gas channels, the plurality of gas channels are interconnected but the optical paths do not interfere with each other, each gas channel contains one or more gases to be measured, and the monochromatic light beams are converted into electrical signals by one or more corresponding optical detection elements in the optical detection element array after passing through one of the gas channels.

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