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Silicon Carbide High Temperature Photodetectors and Image Sensor
KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.ORCID iD: 0000-0001-8854-7446
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. , p. 81
Series
TRITA-EECS-AVL ; 2019:37
Keywords [en]
Silicon Carbide (SiC), high temperature, photodetector, photodiode, phototransistor, ultraviolet (UV), transistor-transistor logic (TTL), bipolar junction transistor (BJT), integrated circuit (IC), pixel sensor, image sensor
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Information and Communication Technology
Identifiers
URN: urn:nbn:se:kth:diva-248426ISBN: 978-91-7873-160-2 (print)OAI: oai:DiVA.org:kth-248426DiVA, id: diva2:1303493
Public defence
2019-05-03, Ka-Sal B (Sal Peter Weissglas), Kistagången 16, Kista, 10:00 (English)
Opponent
Supervisors
Funder
Knut and Alice Wallenberg Foundation, Working on VenusSwedish Foundation for Strategic Research , CMP Lab
Note

QC 20190411

Available from: 2019-04-11 Created: 2019-04-09 Last updated: 2019-04-11Bibliographically approved
List of papers
1. Process Control and Optimization of 4H-SiC Semiconductor Devices and Circuits
Open this publication in new window or tab >>Process Control and Optimization of 4H-SiC Semiconductor Devices and Circuits
Show others...
2019 (English)In: Proceedings of the 3rd Electron Devices Technology and Manufacturing, (EDTM) Conference 2019, IEEE, 2019Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
IEEE, 2019
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-248421 (URN)
Conference
The 3rd Electron Devices Technology and Manufacturing (EDTM) Conference
Note

QC 20190411

Available from: 2019-04-08 Created: 2019-04-08 Last updated: 2019-04-11Bibliographically approved
2. 550 degrees C 4H-SiC p-i-n Photodiode Array With Two-Layer Metallization
Open this publication in new window or tab >>550 degrees C 4H-SiC p-i-n Photodiode Array With Two-Layer Metallization
2016 (English)In: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 37, no 12, p. 1594-1596Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
IEEE, 2016
Keywords
4H-SiC, UV, photodiode, high temperature, two-layer metallization
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-199496 (URN)10.1109/LED.2016.2618122 (DOI)000389332700016 ()2-s2.0-85000786021 (Scopus ID)
Note

QC 20170118

Available from: 2017-01-18 Created: 2017-01-09 Last updated: 2019-04-10Bibliographically approved
3. Scaling and modeling of high temperature 4H-SiC p-i-n photodiodes
Open this publication in new window or tab >>Scaling and modeling of high temperature 4H-SiC p-i-n photodiodes
2018 (English)In: IEEE Journal of the Electron Devices Society, ISSN 2168-6734, Vol. 6, no 1, p. 139-145, article id 8240922Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc., 2018
Keywords
4H-SiC, high temperature, photodiode, scaling, Capacitance, Photodiodes, Silicon carbide, Dark current ratio, Full-depletion voltage, IV characteristics, Static and dynamic behaviors, Surface recombinations, Silicon compounds
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-223196 (URN)10.1109/JEDS.2017.2785618 (DOI)000423582900022 ()2-s2.0-85040046747 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

Export Date: 13 February 2018; Article; Correspondence Address: Hou, S.; School of Information and Communication Technology, KTH Royal Institute of TechnologySweden; email: shuoben@kth.se; Funding details: Knut och Alice Wallenbergs Stiftelse; Funding details: KTH, Kungliga Tekniska Högskolan. QC 20180228

Available from: 2018-02-28 Created: 2018-02-28 Last updated: 2019-04-10Bibliographically approved
4. High Temperature High Current Gain IC Compatible 4H-SiC Phototransistor
Open this publication in new window or tab >>High Temperature High Current Gain IC Compatible 4H-SiC Phototransistor
2019 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

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.

Keywords
4H-SiC, Phototransistor, Integrated Circuit (IC), High Temperature
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-248422 (URN)
Conference
European Conference on Silicon Carbide and Related Materials (ECSCRM 2018)
Note

QC 20190410

Available from: 2019-04-08 Created: 2019-04-08 Last updated: 2019-04-10Bibliographically approved
5. A 4H-SiC BJT as a Switch for On-Chip Integrated UV Photodiode
Open this publication in new window or tab >>A 4H-SiC BJT as a Switch for On-Chip Integrated UV Photodiode
2019 (English)In: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 40, no 1, p. 51-54Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2019
Keywords
4H-SiC, BJT, UV, photodiode, high temperature, switch
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-242990 (URN)10.1109/LED.2018.2883749 (DOI)000456172600013 ()2-s2.0-85057777289 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20190204

Available from: 2019-02-04 Created: 2019-02-04 Last updated: 2019-04-10Bibliographically approved
6. Towards Silicon Carbide VLSI Circuits for Extreme Environment Applications
Open this publication in new window or tab >>Towards Silicon Carbide VLSI Circuits for Extreme Environment Applications
Show others...
2019 (English)In: Electronics, ISSN 2079-9292,, Vol. 8, no 5Article in journal (Other academic) Published
Abstract [en]

A Process Design Kit (PDK) has been developed to realize complex integrated circuits in Silicon Carbide (SiC) bipolar low-power technology. The PDK development process included basic device modeling, and design of gate library and parameterized cells. A transistor–transistor logic (TTL)-based PDK gate library design will also be discussed with delay, power, noise margin, and fan-out as main design criterion to tolerate the threshold voltage shift, beta (β) and collector current (IC) variation of SiC devices as temperature increases. The PDK-based complex digital ICsdesign flow based on layout, physical verification, and in-house fabrication process will also be demonstrated. Both combinational and sequential circuits have been designed, such as a 720-device ALU and a 520-device 4 bit counter. All the integrated circuits and devices are fully characterized up to 500 °C. The inverter and a D-type flip-flop (DFF) are characterized as benchmark standard cells. The proposed work is a key step towards SiC-based very large-scale integrated (VLSI) circuits implementation for high-temperature applications.

Keywords
Process Design Kit (PDK); bipolar logic gates; high temperature digital integrated circuits (ICs); transistor–transistor logic (TTL); SiC bipolar transistor; SiC VLSI Circuits
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-248424 (URN)10.3390/electronics8050496 (DOI)
Funder
Knut and Alice Wallenberg Foundation, Working on Venus
Note

QC 20190410

Available from: 2019-04-08 Created: 2019-04-08 Last updated: 2019-05-23Bibliographically approved

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