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High Temperature High Current Gain IC Compatible 4H-SiC Phototransistor
KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.ORCID iD: 0000-0001-8854-7446
KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
KTH, School of Electrical Engineering and Computer Science (EECS), Electronics.
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.

Place, publisher, year, edition, pages
2019.
Keywords [en]
4H-SiC, Phototransistor, Integrated Circuit (IC), High Temperature
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-248422OAI: oai:DiVA.org:kth-248422DiVA, id: diva2:1302970
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
In thesis
1. Silicon Carbide High Temperature Photodetectors and Image Sensor
Open this publication in new window or tab >>Silicon Carbide High Temperature Photodetectors and Image Sensor
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
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:nbn:se:kth:diva-248426 (URN)978-91-7873-160-2 (ISBN)
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

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