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A 4H-SiC BJT as a Switch for On-Chip Integrated UV Photodiode
KTH, School of Electrical Engineering and Computer Science (EECS).
KTH, School of Electrical Engineering and Computer Science (EECS).ORCID iD: 0000-0001-6705-1660
KTH, School of Electrical Engineering and Computer Science (EECS).ORCID iD: 0000-0001-8108-2631
KTH, School of Electrical Engineering and Computer Science (EECS).ORCID iD: 0000-0002-5845-3032
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. Vol. 40, no 1, p. 51-54
Keywords [en]
4H-SiC, BJT, UV, photodiode, high temperature, switch
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-242990DOI: 10.1109/LED.2018.2883749ISI: 000456172600013Scopus ID: 2-s2.0-85057777289OAI: oai:DiVA.org:kth-242990DiVA, id: diva2:1285319
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20190204

Available from: 2019-02-04 Created: 2019-02-04 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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Hou, ShuobenHellström, Per-ErikZetterling, Carl-MikaelÖstling, Mikael

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