Light-emitting sensitive transistor intelligent heat sensor based on quantum well hot electron emission effect and MOCVD preparation and micro-nano processing method thereof

Abstract

The invention relates to a light-emitting sensitive transistor intelligent heat sensor based on a quantum well hot electron emission effect and an MOCVD preparation and micro-nano processing method thereof, and belongs to the technical field of semiconductor sensing. According to the sensor, a stepped or array type quantum well structure is embedded in a III-V group heterojunction bipolar transistor base region. The core is that the collector current and the current gain of the device are abnormally increased along with the temperature rise by utilizing the capture of a quantum well on current carriers and the hot electron emission effect of the quantum well along with the temperature change, so that the ultrahigh thermal sensitivity is realized. Two transistors of this kind are cascaded into a Darlington pair, and thermal response signals are significantly amplified. The invention also provides a correction charge control model which is used for optimizing key parameters such as quantum well width and the like so as to balance sensitivity and linearity. The device has electrical and optical output, the sensitivity is obviously higher than that of a traditional sensor, the preparation process is compatible with the existing photoelectric integration technology, and an innovative solution is provided for high-precision intelligent temperature measurement.

Description

Technical Field

[0001] This invention relates to the field of semiconductor sensor technology, specifically to a temperature sensor with ultra-high sensitivity and its fabrication method, particularly a light-emitting transistor smart thermal sensor based on III-V compound semiconductors and utilizing the quantum well hot electron emission effect, and its dedicated metal-organic chemical vapor deposition preparation and micro / nano fabrication method. Background Technology

[0002] Precise temperature sensing is a core requirement in fields such as industrial control, environmental monitoring, biomedicine, and advanced integrated circuits. With the rapid development of optoelectronic integrated circuits and intelligent sensing systems, there is an urgent need for new types of temperature sensors that are integrated, highly sensitive, have a fast response speed, and possess multi-parameter sensing capabilities.

[0003] Traditional temperature sensing technologies are primarily based on thermocouples, thermistors, platinum resistance thermometers, and silicon-based semiconductor sensors. Among these, silicon-based CMOS integrated temperature sensors, especially those based on the bandgap principle of bipolar transistors (BPTs), are widely used due to their ease of integration and low cost (such as the bandgap reference circuit described in the background section). However, these sensors are limited by the physical properties of silicon and the temperature behavior of traditional PN junctions, resulting in voltage-temperature sensitivity typically of only about -2 mV / ℃. Furthermore, in high-precision or high-speed applications, they face an inherent trade-off between sensitivity, linearity, and power consumption. In addition, the current gain of traditional BPTs typically decreases with increasing temperature, limiting the improvement of their current-signal-based sensing sensitivity.

[0004] In pursuit of higher sensitivity and integration, academia and industry have explored various technological approaches, including microelectromechanical systems (MEMS)-based thermal radiometers and superconducting transition edge sensors. However, these technologies are often complex in their fabrication processes, operate under harsh conditions, or are difficult to integrate with standard integrated circuit processes. Therefore, within the framework of conventional semiconductor processes, the search for device structures with novel temperature response mechanisms has become an important research direction.

[0005] Heterojunction bipolar transistors (HBTs) have been successfully applied in high-speed electronics due to their excellent frequency characteristics and current drive capability. Notably, in 2004, researchers observed radiative recombination luminescence in the base region of a III-V group indium gallium phosphide / gallium arsenide heterojunction bipolar transistor (HBT), marking the birth of a novel three-terminal device integrating electrical signal amplification and optical output—the light-emitting transistor (LED). Subsequently, by introducing a quantum well structure into the base region of the HBT, a quantum well heterojunction bipolar transistor, or LED, was formed. Initial research on LEDs focused on their potential as light sources or modulators in high-speed optical communication and optoelectronic integrated circuits, and their optical modulation bandwidth has been increased to the tens of GHz range.

[0006] However, in exploring the electrical properties of LETs, our research team discovered a phenomenon distinct from traditional HBTs and even ordinary BJTs: for LETs with a specific quantum well structure embedded in the base region, the collector current and current gain increase significantly with increasing ambient temperature. Theoretical analysis shows that this anomalous thermal behavior stems from the quantum well's trapping of injected electrons and its temperature-dependent thermionic emission effect. At low temperatures, the quantum well effectively traps electrons, some of which recombine and do not contribute to the collector current. As the temperature rises, the trapped electrons gain sufficient energy to escape the quantum well barrier through thermionic emission, re-entering the base transport channel and ultimately being collected by the collector, thus causing the collector current to increase with temperature. This unique physical mechanism provides a revolutionary theoretical basis for developing novel semiconductor temperature sensors.

[0007] Although the hot electron emission effect based on quantum traps has been preliminarily understood in principle, transforming it into a high-performance, practical thermal sensor still faces a series of significant challenges, which constitute gaps and deficiencies in the existing technology:

[0008] First, there is a gap in the design of device structure:

[0009] Existing LET devices in research primarily focus on optimizing light emission efficiency, and their quantum well structures (such as shape, width, number, and position) are not designed to maximize temperature sensitivity. For example, simple square quantum wells and stepped quantum wells designed to suppress polarization field effects have different impacts on carrier capture and escape dynamics, thus affecting thermal sensitivity. A systematic approach to precisely designing quantum well parameters (width, composition, and arrangement) through bandgap engineering to balance high sensitivity and good linearity has yet to be developed.

[0010] Second, the theoretical model is missing:

[0011] Traditional transistor charge control models cannot describe the capture, recombination, and temperature-dependent escape processes of charge carriers in quantum wells. Without an accurate analytical model that includes thermionic emission effects, it is difficult to guide the optimized design of high-performance thermal sensing LEDs, and it is also impossible to accurately predict and explain their temperature response characteristics.

[0012] Third, there is a lack of methods to enhance sensitivity:

[0013] The absolute current change of a single LET device is finite. The key to improving sensor resolution and signal-to-noise ratio lies in how to further amplify temperature-induced electrical signal changes without significantly increasing power consumption and complexity. Current technologies lack dedicated signal amplification architectures specifically designed for the thermal sensing characteristics of LETs.

[0014] Fourth, the specialized preparation process is not yet mature:

[0015] Realizing the aforementioned high-performance LED thermal sensors relies on precise material growth and complex micro / nano fabrication processes. This includes: how to grow complex heterojunction epitaxial structures containing multilayers, thin layers, and quantum wells with specific compositions on substrates such as GaAs using MOCVD processes; and how to precisely define device mesa, form reliable ohmic contacts, and achieve device isolation and interconnection through a series of micro / nano fabrication steps such as photolithography, wet / dry etching, metallization, and passivation, especially to fabricate high-performance devices with emitter areas of only tens of micrometers square. These process conditions and parameter control methods differ from conventional HBT or LED processes, and there is a lack of a dedicated fabrication process that is optimized, repeatable, and has a high yield.

[0016] Therefore, there is an urgent need for an innovative device design scheme, a supporting theoretical model, a signal extraction architecture, and a complete and reliable dedicated fabrication method to fully exploit and utilize the quantum trap thermionic emission effect, and to manufacture intelligent thermal sensors with sensitivity far exceeding existing technologies, good linearity, easy integration, and stable performance. This invention addresses the gaps and deficiencies in the aforementioned existing technologies. Summary of the Invention

[0017] This invention designs a light-emitting transistor (LED) smart thermal sensor based on the quantum well hot electron emission effect and its MOCVD fabrication and micro / nano processing method. The technical problem it solves is the limited sensitivity of traditional silicon-based and heterojunction temperature sensors, and the difficulty in simultaneously achieving high sensitivity and good linearity. In particular, the current gain of traditional heterojunction bipolar transistors decreases with increasing temperature, fundamentally limiting their current-signal-based temperature sensing sensitivity.

[0018] To solve the aforementioned technical problems, the present invention adopts the following solution:

[0019] A smart thermal sensor based on the thermionic emission effect of a quantum well light-emitting transistor includes: a light-emitting transistor, wherein the light-emitting transistor is a heterojunction bipolar transistor structure with at least one quantum well structure embedded in its base region; the quantum well structure is used to capture injected charge carriers and, upon temperature change, alters the number of charge carriers escaping from the quantum well through the thermionic emission effect, thereby causing the collector current or current gain of the light-emitting transistor to monotonically increase with increasing temperature, achieving a positive temperature coefficient response; and a signal extraction and processing circuit, electrically connected to the electrodes of the light-emitting transistor, used to provide an operating bias for the light-emitting transistor and convert the change in its collector current or current gain into an electrical signal output corresponding to temperature.

[0020] Preferably, the quantum well structure is a stepped quantum well.

[0021] Preferably, the well width of the quantum well structure is 8 nanometers to 12 nanometers.

[0022] Preferably, the number of quantum well structures embedded in the base region is multiple, forming a multi-quantum well structure.

[0023] Preferably, the signal extraction and processing circuit includes a Darlington amplification structure, wherein the input stage transistor of the Darlington amplification structure is the light-emitting transistor, which is used to amplify the output current of the light-emitting transistor.

[0024] Preferably, the signal extraction and processing circuit further includes a transimpedance amplifier, an analog-to-digital converter, and a microprocessor; the transimpedance amplifier converts the collector current change of the light-emitting transistor into a voltage signal; the analog-to-digital converter converts the voltage signal into a digital signal; the microprocessor processes the digital signal, performs linearization calibration and temperature conversion, and outputs a digital temperature value.

[0025] Preferably, the heterojunction bipolar transistor structure includes: a substrate; an n-type collector region, a p-type base region, and an n-type emitter region sequentially formed on the substrate, wherein the p-type base region is composed of a III-V compound semiconductor material and embedded in the quantum well structure; and the n-type emitter region is composed of a wide-bandgap III-V compound semiconductor material that forms a heterojunction with the p-type base region.

[0026] Preferably, the material of the p-type base region is GaAs, the material of the quantum well structure is InxGa1-xAs, where 0.15≤x≤0.25; and the material of the n-type emitter region is InGaP or AlGaAs.

[0027] A method for MOCVD fabrication and micro / nano processing of a light-emitting transistor smart thermal sensor based on the quantum well hot electron emission effect, characterized by comprising the following steps:

[0028] S1, Provide a substrate;

[0029] S2. Using a metal-organic chemical vapor deposition process, a current collector region, a base region containing at least one quantum well structure, an emitter region, and a contact layer are sequentially epitaxially grown on the substrate to form a heterojunction bipolar transistor epitaxial wafer.

[0030] S3. Perform micro-nano fabrication on the epitaxial wafer, the micro-nano fabrication including at least: defining emitter, base and collector mesa by photolithography and etching processes; forming ohmic contact electrodes electrically connected to each mesa; performing device isolation and surface passivation; forming interconnect metal lines to lead out electrodes.

[0031] Preferably, in step S2, the quantum well structure adopts a stepped band structure, and its growth process includes a growth-pause-growth mode with a growth temperature of 550°C to 580°C.

[0032] Preferably, in step S3, the etching process includes an inductively coupled plasma dry etching process using Cl2 / BCl3 gas to define the emitter mesa, and a wet chemical etching process using H3PO4:H2O2:H2O solution to define the base and collector mesa.

[0033] Preferably, in step S3, the step of forming an n-type ohmic contact includes: depositing a Ni / Ge / Au multilayer metal film and performing rapid thermal annealing at 430°C to 450°C; the step of forming a p-type ohmic contact includes: depositing a Ti / Pt / Au multilayer metal film and performing rapid thermal annealing at 400°C to 420°C.

[0034] This quantum well-based light-emitting transistor smart thermal sensor and its MOCVD fabrication and micro / nano processing method have the following advantages:

[0035] (1) This invention breaks through the physical limitation that traditional temperature sensors rely on the material resistivity or PN junction voltage to decrease monotonically with temperature. For the first time, it utilizes the thermionic emission effect of quantum well in transistor architecture to realize a positive temperature coefficient response in which the collector current and current gain increase with temperature.

[0036] (2) This invention establishes a matching modified charge control model. This model successfully quantifies the capture, recombination, and thermally induced escape processes of charge carriers in the quantum well, and its theoretical simulation results are in high agreement with experimental data. This model not only explains the working principle of the device, but more importantly, it provides a quantifiable design tool for performance optimization, enabling device development to transform from empirical exploration into a predictable and designable systems engineering.

[0037] (3) This invention proposes a monolithic Darlington integration scheme that cascades two light-sensitive transistors. This architecture fully utilizes the current amplification characteristics of transistors to directly amplify the weak temperature-sensing current signal inside the chip. This integrated amplification scheme effectively improves the signal-to-noise ratio and resolution of the sensor and simplifies the dependence on external amplification circuits.

[0038] (4) This invention overcomes the response nonlinearity problem often faced by high-sensitivity sensors through the careful design of the quantum well structure. Through theoretical simulation and experimental verification, the synergistic optimization of sensitivity and linearity can be achieved in a wide temperature range, thereby meeting the dual high requirements of accuracy and stability of sensors in the field of precision measurement.

[0039] (5) The preparation method of this invention is entirely based on the mature III-V compound semiconductor MOCVD epitaxial process and standard micro-nano fabrication process, and is compatible with existing optoelectronic chip production lines, possessing good process feasibility and industrialization prospects. Furthermore, this device is essentially a three-terminal device with light-emitting function. Its electrical ports are used to achieve ultra-high sensitivity temperature sensing, while the simultaneously existing optical output port provides a unique functional expansion interface for future development of non-contact optical temperature readings or the construction of intelligent sensing systems that integrate multiple parameters such as temperature and light intensity / wavelength, greatly enhancing its application potential in advanced optoelectronic integrated systems. Attached Figure Description

[0040] Figure 1 : Schematic diagram of the epitaxial structure of the stepped single quantum well heterojunction bipolar transistor of the present invention.

[0041] Figure 2 The collector current-voltage characteristic curve of the SQW-HBT of this invention varies with temperature.

[0042] Figure 3 The current gain of the SQW-HBT of this invention varies with temperature.

[0043] Figure 4 : A schematic diagram of minority carrier distribution in the SQW-HBT modified charge control model of this invention.

[0044] Figure 5 The experimental and simulated current gain comparison diagram of the SQW-HBT of this invention is shown.

[0045] Figure 6 : Schematic diagram of the epitaxial structure of the three quantum well heterojunction bipolar transistor of the present invention.

[0046] Figure 7 : Collector current-voltage characteristic curve of the TQW-HBT of this invention.

[0047] Figure 8 Comparison of experimental and simulated current gain of the TQW-HBT of this invention.

[0048] Figure 9 Top optical microscopic view of the LET and Darlington transistors prepared according to this invention.

[0049] Figure 10 Output characteristic curve of a single light-emitting transistor of the present invention.

[0050] Figure 11 The output characteristic curve of the Darlington transistor of this invention.

[0051] Figure 12Comparison of current gain-temperature characteristics between LET and Darlington transistor in this invention.

[0052] Figure 13 The present invention provides a simulation diagram of the collector current-temperature relationship under different quantum well widths.

[0053] Figure 14 Comparison of thermal sensitivity (dIC / dT) under different quantum well widths in this invention. Detailed Implementation

[0054] The following is combined with Figures 1 to 14 The present invention will be further described as follows:

[0055] Example 1: Structure and fabrication of a stepped single-quantum-well heterojunction bipolar transistor thermal sensor

[0056] First, a stepped single-quantum-well heterojunction bipolar transistor is provided as the basic thermistor unit. For example... Figure 1 As shown, this illustrates the core of the device in this embodiment—the epitaxial layered structure. This structure is grown on a semi-insulating GaAs substrate using an npn-type indium gallium phosphide / gallium arsenide material system. The light-sensitive transistor of this invention is a heterojunction bipolar transistor structure, comprising: a substrate; an n-type collector region, a p-type base region, and an n-type emitter region sequentially formed on the substrate, wherein the p-type base region is composed of a III-V compound semiconductor material and embedded in a quantum well structure; the n-type emitter region is composed of a wide-bandgap III-V compound semiconductor material forming a heterojunction with the p-type base region. Specifically, the material of the p-type base region is GaAs, and the material of the n-type emitter region is InGaP or AlGaAs.

[0057] This invention designs and embeds a stepped single quantum well composed of materials with different indium compositions within a heavily doped p-type GaAs base layer. Specifically, the well width of this quantum well structure is 8 to 12 nanometers, and in this embodiment, the quantum well structure may include a relatively thick layer of In. 0.2 Ga 0.8 An As layer (e.g., 120 Å) and two thinner In layers 0.1 Ga 0.9 The As layers (e.g., 20 Å each) have a total thickness of approximately 160 Å (approximately 16 nanometers). The quantum well structure is made of InxGa. 1-x As, where 0.15≤x≤0.25. This stepped band structure helps optimize carrier capture and escape dynamics and is the structural basis for achieving high thermal sensitivity.

[0058] The device was fabricated using MOCVD and micro / nano fabrication methods, including the following steps:

[0059] S1. Provide a substrate (semi-insulating GaAs substrate).

[0060] S2. Using metal-organic chemical vapor deposition (MOCVD) process, a collector region, a base region containing at least one quantum well structure, an emitter region and a contact layer are epitaxially grown sequentially on the substrate to form a heterojunction bipolar transistor epitaxial wafer; wherein, the quantum well structure adopts a stepped energy band design, and its growth process includes a growth-pause-growth mode, with a growth temperature of 550℃ to 580℃.

[0061] S3. Perform micro / nano fabrication on the epitaxial wafer, the micro / nano fabrication including at least: defining the emitter, base, and collector mesa through photolithography and etching processes; the etching processes include defining the emitter mesa using inductively coupled plasma dry etching with Cl2 / BCl3 gas, and defining the base and collector mesa using wet chemical etching with H3PO4:H2O2:H2O solution; forming ohmic contact electrodes electrically connected to each mesa; wherein, the step of forming n-type ohmic contacts includes: depositing a Ni / Ge / Au multilayer metal film and performing rapid thermal annealing at 430°C to 450°C; the step of forming p-type ohmic contacts includes: depositing a Ti / Pt / Au multilayer metal film and performing rapid thermal annealing at 400°C to 420°C; performing device isolation and surface passivation; and forming interconnect metal lines to lead out the electrodes.

[0062] The device was fabricated using metal-organic chemical vapor deposition and standard micro / nano fabrication processes. (See attached diagram.) Figure 1 After the epitaxial material shown is grown, the device mesa is defined by photolithography and wet chemical etching (e.g., using an H2SO4:H2O2:H2O solution). Subsequently, n-type ohmic contacts (e.g., Au / Ge / Ni / Au) for the emitter / collector and p-type ohmic contacts (e.g., Ti / Pt / Au) for the base are formed through electron beam evaporation, lift-off, and rapid thermal annealing processes. Finally, device isolation, surface passivation (e.g., SiNx deposition), and metal interconnects are performed to complete the device fabrication.

[0063] Example 2: Verification and Principle Analysis of the Thermosensitive Characteristics of a Stepped Single Quantum Well Device

[0064] The device prepared in Example 1 was electrically characterized to verify its unique thermosensitive properties. (Refer to...) Figure 2 It is the collector current (I) measured at different ambient temperatures (e.g., 25℃ and 85℃). C ) and collector-emitter voltage (V CE The relationship curve clearly shows that, under the same bias conditions, the collector current of the device increases significantly with increasing temperature, which is the opposite of the behavior of a traditional transistor. This demonstrates the characteristic that the collector current increases monotonically with increasing temperature, achieving a positive temperature coefficient response.

[0065] Reference Figure 3 Furthermore, it quantitatively demonstrated the relationship between the current gain (β) of the device and increasing temperature. The experimental data clearly show that the current gain increases monotonically with increasing temperature, directly proving the thermal enhancement effect. This also corresponds to the characteristic that the current gain increases monotonically with increasing temperature.

[0066] To explain this anomalous physical phenomenon, this invention proposes a modified charge control model.

[0067] Reference Figure 4 This diagram schematically illustrates the charge distribution of minority carriers (electrons) in the base region of a transistor under this model. Charge Q0 represents electrons that diffuse directly to the collector, while charge Q1 represents electrons trapped in the quantum well. QW This represents the charge of the electrons bound in the quantum well. The core of this model is the introduction of a thermionic emission mechanism: as the temperature increases, the trapped electrons (Qt) emit more electrons. QW To obtain sufficient thermal energy, the escape time (τ) esc The exponential shortening causes more electrons to escape from the quantum well and join the diffusion current of Q0, resulting in an increase in the collector current I. C And the current gain β increases. This mechanism is the physical essence of how the quantum well structure is used to trap injected charge carriers, and how the number of charge carriers escaping the quantum well changes with temperature through the thermionic emission effect, thereby causing the collector current or current gain of the light-sensitive transistor to increase monotonically with increasing temperature.

[0068] To verify the correctness of the model, experimental data were compared with theoretical simulations.

[0069] Reference Figure 5 The figure compares the experimentally measured current gain (data points) with the simulation results (curves) based on the modified charge control model described above. The two results show a high degree of agreement within the temperature range of 25℃ to 85℃, which not only confirms the accuracy of the theoretical model but also establishes the feasibility of using this model to guide the design of high-performance thermistors.

[0070] Example 3: Three-quantum-well heterojunction bipolar transistor thermal sensor

[0071] To achieve higher thermal sensitivity, this invention provides an enhanced structure. Specifically, multiple quantum well structures are embedded within the base region, forming a multi-quantum well structure.

[0072] See attached document Figure 6 This invention demonstrates the epitaxial structure of a three-quantum-well heterojunction bipolar transistor. The key feature of this invention is the sequential arrangement of three undoped In atoms along the current propagation direction within the base layer. 0.2 Ga 0.8As quantum wells (e.g., each well is 70 Å wide) are separated by GaAs barrier layers (e.g., 35 Å). The multi-quantum-well structure enhances the overall carrier trapping capability, thereby inducing stronger charge redistribution and current modulation with temperature changes.

[0073] The characteristics of the TQW-HBT device were characterized.

[0074] Reference Figure 7 This shows the output characteristic curves of the device at two characteristic temperatures. (See attached diagram.) Figure 2 In comparison, the collector current exhibits a stronger temperature dependence.

[0075] Reference Figure 8 The comparison between the experimental current gain and the theoretical simulated gain once again showed good agreement. Experimental results indicate that, within the same temperature rise range (25℃ to 85℃), the TQW-HBT can achieve approximately 200% increase in collector current, with an average current sensitivity of 7μA / ℃, outperforming single quantum well structures.

[0076] Example 4: Darlington Integrated Thermal Sensor and its Signal Amplification

[0077] To achieve on-chip amplification of thermistor signals, this invention provides a Darlington integrated solution. The signal extraction and processing circuit includes a Darlington amplification structure, where the input stage transistor is a light-emitting transistor (LED) used to amplify the output current of the LED.

[0078] Reference Figure 9 The image shows an optical microscopic top view of a single fabricated light-emitting transistor (left) and a Darlington transistor (right) composed of two identical LETs cascaded together. The Darlington pair is integrated on a single chip, with the emitter of the first LET directly connected to the base of the second LET.

[0079] The output characteristics of the two structures were tested separately to quantify the amplification effect. (Refer to...) Figure 10 It is the output characteristic curve of a single LET at different temperatures (I C,1 vs. V C1E1 ).

[0080] Reference Figure 11 It is the output characteristic curve of a Darlington transistor at the same temperature series (I C vs. V CE2Comparing the two figures, it is evident that at the same temperature, the output current of the Darlington structure is significantly greater than that of a single transistor. The inset shows the external bias circuit during testing, where a 500Ω resistor (R) connected to the collector of the second LET is used to convert the amplified current signal into a voltage signal. This resistor can be considered a simplified form of a transimpedance amplifier. A more complete signal extraction and processing circuit includes a transimpedance amplifier, an analog-to-digital converter, and a microprocessor; the transimpedance amplifier converts the collector current change of the light-emitting transistor into a voltage signal; the analog-to-digital converter converts the voltage signal into a digital signal; the microprocessor processes the digital signal, performs linearization calibration and temperature conversion, and outputs a digital temperature value.

[0081] The most critical performance comparison is reflected in the temperature dependence of current gain.

[0082] Reference Figure 12 This study directly compared the current gain of a single LET with that of a Darlington transistor as a function of temperature. It clearly shows that the current gain of the Darlington configuration and its slope with increasing temperature (i.e., thermal sensitivity) are both improved by orders of magnitude. Experiments showed that at a base current of 1 mA, the current sensitivity of the Darlington structure reached 26.2 μA / ℃, more than three times that of a single LET (8.53 μA / ℃), and the voltage sensitivity after resistor conversion reached 9.12 mV / ℃.

[0083] Example 5: Quantum well width optimization design method

[0084] Quantum well width is a key design parameter for balancing thermal sensitivity and response linearity. This invention provides optimization design criteria through system simulation.

[0085] Reference Figure 13 The simulation investigated the relationship between the collector current and temperature as the quantum well width (d) varied from 50 Å to 120 Å. The simulation showed that narrower quantum wells (e.g., 50 Å) typically exhibited higher initial sensitivity, but the current-temperature relationship was more nonlinear.

[0086] For quantitative comparison, from Figure 13 Extract the derivative of current with respect to temperature (d) from the simulation data. IC / d T ), that is, thermal sensitivity.

[0087] Reference Figure 14The study presents the thermal sensitivity versus temperature curves for different quantum well widths. Analysis shows that as the quantum well width increases, the peak sensitivity decreases, but the response linearity improves. Considering all factors, a quantum well width of approximately 90 Å achieves the optimal balance between high sensitivity and excellent linearity over a wide temperature range, providing a clear parameter selection basis for the design of high-performance thermal sensors. These optimization results further support setting a well width range of 8 nm to 12 nm.

[0088] In summary, this invention, through a progressive technical approach from microscopic band structure design (stepped, multi-quantum well), to device-level innovation (heterojunction bipolar transistor), and then to circuit-level amplification (Darlington integration), combined with dedicated MOCVD epitaxy and micro / nano fabrication methods, has successfully realized an intelligent thermal sensor with ultra-high sensitivity, good linearity, and easy integration.

[0089] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the implementation of the present invention is not limited to the above-described manner. Any improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A smart thermal sensor based on the quantum well hot electron emission effect of a light-emitting transistor, characterized in that, include: A light-emitting transistor, wherein the light-emitting transistor is a heterojunction bipolar transistor structure, and at least one quantum well structure is embedded in its base region; The quantum well structure is used to capture injected charge carriers and change the number of charge carriers escaping the quantum well through the thermionic emission effect when the temperature changes, thereby making the collector current or current gain of the light-sensitive transistor increase monotonically with the increase of temperature, achieving a positive temperature coefficient response. The signal extraction and processing circuit is electrically connected to the electrodes of the light-emitting transistor, and is used to provide a working bias for the light-emitting transistor and convert the change of its collector current or current gain into an electrical signal output corresponding to temperature.

2. The light-emitting transistor-based intelligent thermal sensor according to claim 1, characterized in that: The quantum well structure is a stepped quantum well.

3. The light-emitting transistor-based intelligent thermal sensor according to claim 1 or 2, characterized in that: The quantum well structure has a well width of 8 nanometers to 12 nanometers.

4. The light-emitting transistor-based intelligent thermal sensor according to claim 1, characterized in that: The number of quantum well structures embedded in the base region is multiple, forming a multi-quantum well structure.

5. The light-emitting transistor-based intelligent thermal sensor according to claim 1, characterized in that: The signal extraction and processing circuit includes a Darlington amplification structure, wherein the input stage transistor of the Darlington amplification structure is the light-emitting transistor, which is used to amplify the output current of the light-emitting transistor.

6. The light-emitting transistor-based intelligent thermal sensor according to claim 1, characterized in that: The signal extraction and processing circuit also includes a transimpedance amplifier, an analog-to-digital converter, and a microprocessor; The transimpedance amplifier converts the change in collector current of the light-emitting transistor into a voltage signal; The analog-to-digital converter converts the voltage signal into a digital signal; The microprocessor processes the digital signal, performs linearization calibration and temperature conversion, and outputs a digital temperature value.

7. The light-emitting transistor-based intelligent thermal sensor according to claim 1, characterized in that: The heterojunction bipolar transistor structure includes: Substrate; An n-type collector region, a p-type base region, and an n-type emitter region are sequentially formed on the substrate, wherein the p-type base region is composed of a III-V compound semiconductor material and embedded in the quantum well structure; The n-type emitter region is composed of a wide-bandgap III-V compound semiconductor material that forms a heterojunction with the p-type base region.

8. The light-emitting transistor-based intelligent thermal sensor according to claim 7, characterized in that: The p-type base region is made of GaAs, and the quantum well structure is made of InxGa1-xAs, where 0.15 ≤ x ≤ 0.25; the n-type emitter region is made of InGaP or AlGaAs.

9. A method for MOCVD fabrication and micro / nano processing of a light-emitting transistor smart thermal sensor based on the quantum well hot electron emission effect, as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1, Provide a substrate; S2. Using a metal-organic chemical vapor deposition process, a current collector region, a base region containing at least one quantum well structure, an emitter region, and a contact layer are sequentially epitaxially grown on the substrate to form a heterojunction bipolar transistor epitaxial wafer. S3. Perform micro-nano fabrication on the epitaxial wafer, the micro-nano fabrication including at least: defining emitter, base and collector mesa by photolithography and etching processes; forming ohmic contact electrodes electrically connected to each mesa; performing device isolation and surface passivation; forming interconnect metal lines to lead out electrodes.

10. The MOCVD preparation and micro / nano fabrication method according to claim 9, characterized in that: In step S2, the quantum well structure adopts a stepped band structure, and its growth process includes a growth-pause-growth mode with a growth temperature of 550°C to 580°C.

11. The MOCVD preparation and micro / nano fabrication method according to claim 9, characterized in that: In step S3, the etching process includes an inductively coupled plasma dry etching process using Cl2 / BCl3 gas to define the emitter mesa, and a wet chemical etching process using H3PO4:H2O2:H2O solution to define the base and collector mesa.

12. The MOCVD preparation and micro / nano fabrication method according to claim 9, characterized in that: In step S3, the step of forming an n-type ohmic contact includes: depositing a Ni / Ge / Au multilayer metal film and performing rapid thermal annealing at 430°C to 450°C; the step of forming a p-type ohmic contact includes: depositing a Ti / Pt / Au multilayer metal film and performing rapid thermal annealing at 400°C to 420°C.

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