| 1. |
- Ekström, Mattias, et al.
(author)
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Low temperature Ni-Al ohmic contacts to p-TYPE 4H-SiC using semi-salicide processing
- 2018
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In: International Conference on Silicon Carbide and Related Materials, ICSCRM 2017. - : Trans Tech Publications. - 9783035711455 ; , s. 389-392
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Conference paper (peer-reviewed)abstract
- Most semiconductor devices require low-resistance ohmic contact to p-type doped regions. In this work, we present a semi-salicide process that forms low-resistance contacts (~10-4 Ω cm2) to epitaxially grown p-type (>5×1018 cm-3) 4H-SiC at temperatures as low as 600 °C using rapid thermal processing (RTP). The first step is to self-align the nickel silicide (Ni2Si) at 600 °C. The second step is to deposit aluminium on top of the silicide, pattern it and then perform a second annealing step in the range 500 °C to 700 °C.
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| 2. |
- Hou, Shuoben, et al.
(author)
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4H-SiC PIN diode as high temperature multifunction sensor
- 2017
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In: 11th European Conference on Silicon Carbide and Related Materials, ECSCRM 2016. - : Trans Tech Publications Ltd. - 9783035710434 ; , s. 630-633
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Conference paper (peer-reviewed)abstract
- An in-house fabricated 4H-SiC PIN diode that has both optical sensing and temperature sensing functions from room temperature (RT) to 550 ºC is presented. The two sensing functions can be simply converted from one to the other by switching the bias voltage on the diode. The optical responsivity of the diode at 365 nm is 31.8 mA/W at 550 ºC. The temperature sensitivity of the diode is 2.7 mV/ºC at the forward current of 1 μA.
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| 3. |
- Hou, Shuoben, et al.
(author)
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550 degrees C 4H-SiC p-i-n Photodiode Array With Two-Layer Metallization
- 2016
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In: IEEE Electron Device Letters. - : IEEE. - 0741-3106 .- 1558-0563. ; 37:12, s. 1594-1596
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Journal article (peer-reviewed)abstract
- The p-i-n ultraviolet (UV) photodiodes based on 4H-SiC have been fabricated and characterized from room temperature (RT) to 550 degrees C. Due to bandgap narrowing at higher temperatures, the photocurrent of the photodiode increases by 9 times at 365 nm and reduces by 2.6 times at 275 nm from RT to 550 degrees C. Moreover, a 4H-SiC p-i-n photodiode array has been fabricated. Each column and row of the array is separately connected by two-layer metallization.
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| 4. |
- Hou, Shuoben, et al.
(author)
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A 4H-SiC BJT as a Switch for On-Chip Integrated UV Photodiode
- 2019
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In: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 40:1, s. 51-54
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Journal article (peer-reviewed)abstract
- This letter presents the design, fabrication, and characterization of a 4H-SiC n-p-n bipolar junction transistor as a switch controlling an on-chip integrated p-i-n photodiode. The transistor and photodiode share the same epitaxial layers and topside contacts for each terminal. By connecting the collector of the transistor and the anode of the photodiode, the photo current from the photodiode is switched off at low base voltage (cutoff region of the transistor) and switched on at high base voltage (saturation region of the transistor). The transfer voltage of the circuit decreases as the ambient temperature increases (2 mV/degrees C). Both the on-state and off-state current of the circuit have a positive temperature coefficient and the on/off ratio is >80 at temperature ranged from 25 degrees C to 400 degrees C. It is proposed that the on/off ratio can be increased by similar to 1000 times by adding a light blocking layer on the transistor to reduce light induced off-state current in the circuit.
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| 5. |
- Hou, Shuoben, et al.
(author)
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A Silicon Carbide 256 Pixel UV Image Sensor Array Operating at 400 degrees C
- 2020
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In: IEEE Journal of the Electron Devices Society. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2168-6734. ; 8:1, s. 116-121
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Journal article (peer-reviewed)abstract
- An image sensor based on wide band gap silicon carbide (SiC) has the merits of high temperature operation and ultraviolet (UV) detection. To realize a SiC-based image sensor the challenge of opto-electronic on-chip integration of SiC photodetectors and digital electronic circuits must be addressed. Here, we demonstrate a novel SiC image sensor based on our in-house bipolar technology. The sensing part has 256 ( $16\times 16$ ) pixels. The digital circuit part for row and column selection contains two 4-to-16 decoders and one 8-bit counter. The digital circuits are designed in transistor-transistor logic (TTL). The entire circuit has 1959 transistors. It is the first demonstration of SiC opto-electronic on-chip integration. The function of the image sensor up to 400 degrees C has been verified by taking photos of the spatial patterns masked from UV light. The image sensor would play a significant role in UV photography, which has important applications in astronomy, clinics, combustion detection and art.
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| 6. |
- Hou, Shuoben, et al.
(author)
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High Temperature High Current Gain IC Compatible 4H-SiC Phototransistor
- 2019
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Conference paper (peer-reviewed)abstract
- This paper presents our in-house fabricated 4H-SiC n-p-n phototransistors. The wafer mapping of the phototransistor on two wafers shows a mean maximum forward current gain (βFmax) of 100 at 25 ºC. The phototransistor with the highest βFmax of 113 has been characterized from room temperature to 500 ºC. The βFmax drops to 51 at 400 ºC and remains the same at 500 ºC. The photo current gain of the phototransistor is 3.9 at 25 ºC and increases to 14 at 500 ºC under the 365 nm UV light with the optical power of 0.31 mW. The processing of the phototransistor is same to our 4HSiC-based bipolar integrated circuits, so it is a promising candidate for 4H-SiC opto-electronics onchip integration.
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| 7. |
- Hou, Shuoben, et al.
(author)
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Process Control and Optimization of 4H-SiC Semiconductor Devices and Circuits
- 2019
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In: Proceedings of the 3rd Electron Devices Technology and Manufacturing, (EDTM) Conference 2019. - : IEEE.
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Conference paper (peer-reviewed)abstract
- Processing techniques for 4H-SiC devices and circuits are optimized. The SiC mesa etching process has a variation of < 5% over the wafer. The average n-type contact resistivity is 1.15 × 10-6 Ohm.cm2. The fabricated devices and circuits with one-layer metal interconnect have high yield with no need of chemical-mechanical planarization process. More complex circuits with two-layer metal interconnect achieve high yield by applying chemical-mechanical planarization process.
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| 8. |
- Hou, Shuoben, et al.
(author)
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Scaling and modeling of high temperature 4H-SiC p-i-n photodiodes
- 2018
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In: IEEE Journal of the Electron Devices Society. - : Institute of Electrical and Electronics Engineers Inc.. - 2168-6734. ; 6:1, s. 139-145
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Journal article (peer-reviewed)abstract
- 4H-SiC p-i-n photodiodes with various mesa areas (40,000μm2, 2500μm2, 1600μm2, and 400μm2) have been fabricated. Both C-V and I-V characteristics of the photodiodes have been measured at room temperature, 200 °C, 400 °C, and 500 °C. The capacitance and photo current (at 365 nm) of the photodiodes are directly proportional to the area. However, the dark current density increases as the device is scaled down due to the perimeter surface recombination effect. The photo to dark current ratio at the full depletion voltage of the intrinsic layer (-2.7 V) of the photodiode at 500 °C decreases 7 times as the size of the photodiode scales down 100 times. The static and dynamic behavior of the photodiodes are modeled with SPICE parameters at the four temperatures.
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| 9. |
- Hou, Shuoben, et al.
(author)
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Scaling of 4H-SiC p-i-n photodiodes for high temperature applications
- 2017
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In: 2017 75th Annual Device Research Conference (DRC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509063277
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Conference paper (peer-reviewed)abstract
- Ultraviolet (UV) detection is important in astronomy, combustion detections and medical analysis. Solid-state UV detectors based on wide band gap semiconductors, such as 4H-SiC, are widely studied because of their excellent electrical properties [1]. 4H-SiC based UV detectors are solar blind and can be applied in extremely high temperature environments [2]. However, the state-of-art 4H-SiC photodetectors still have large sizes (>10000 μm2), which are not suitable to be integrated into high resolution UV photography sensors. To build a full-frame UV imaging sensor containing megapixels, photodiodes smaller than 20 μm by side are necessary. Here, we report the fabrication and characterization of 4H-SiC p-i-n photodiodes with mesa areas scaled from 40000 μm2 to 400 μm2. The relationships between the parameters and the areas of the photodiodes are discussed. The photodiodes are fully functional from room temperature (RT) to 500 °C.
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| 10. |
- Hou, Shuoben
(author)
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Silicon Carbide High Temperature Photodetectors and Image Sensor
- 2019
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Doctoral thesis (other academic/artistic)abstract
- Silicon Carbide (SiC) has the advantages of ultraviolet (UV) sensing and high temperature characteristics because of its wide band gap. Both merits make SiC photodetectors very attractive in astronomy, oil drilling, combustion detection, biology and medical applications. Driven by the objective of probing the high temperature surface of Venus (460 °C), this thesis develops SiC photodetectors and an image sensor for extremely high temperature functions. The devices and circuits are demonstrated through the procedure of layout design, in-house processing and characterizations on two batches.The process flow has been optimized to be suitable for large scale integration (LSI) of SiC bipolar integrated circuits (IC). The improved processing steps are SiC dry etching, ohmic contacts and two-level metal interconnect with chemical-mechanical polishing (CMP). The optimized process flow is applied in the fabrication of discrete devices, a transistor-transistor logic (TTL) process design kit (PDK) and LSI circuits.The photodetectors developed in this thesis, including photodiodes with various mesa areas, a phototransistor and a phototransistor Darlington pair have stable characteristics in a wide temperature range (25 °C ~ 500 °C). The maximum operational temperature of the p-i-n photodiode (550 °C) is the highest recorded temperature accomplished ever by a photodiode. The optical responsivity of the photodetectors covers the spectrum from 220 nm to 380 nm, which is UV-only.The SiC pixel sensor and image sensor developed in this thesis are pioneer works. The pixel sensor overcomes the challenge of monolithic integration of SiC photodiode and transistors by sharing the same epitaxial layers and topside contacts. The pixel sensor is characterized from 25 °C to 500 °C. The whole image sensor circuit has 256 (16 ×16) pixel sensors and one 8-bit counter together with two 4-to-16 decoders for row/column selection. The digital circuits are built by the standard logic gates selected from the TTL PDK. The image sensor has 1959 transistors in total. The function of the image sensor up to 400 °C is verified by taking basic photos of nonuniform UV illumination on the pixel sensor array.This thesis makes an important attempt on the demonstration of SiC opto-electronic on-chip integration. The results lay a foundation on the development of future high temperature high resolution UV image sensors.
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