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ZnMgS-Based UV Detectors

Solar-blind UV detectors with a long wavelength cutoff below 280nm have a board range of applications, from fire detection, flame combustion control, scientific instrumentation and missile detection, to UV astronomy. Traditionally, photomultiplier tubes (PMT) and gas-ionization chambers have been used in combination with blocking filters and phosphor down-conversion for such applications. However, they suffer from high cost, fragility, short lifetime and the need for high operating voltages. Diamond diode also suffers from very high cost due to time consuming polishing in its production process. Using AlGaN alloys as the active material for solar-blind detection of UV radiation has a difficult problem, which is the lack of a lattice matched substrate. As a result, the response time and the visible rejection power are limited. Recently developed ZnSSe Schottky barrier photodiodes can be used to form visible blind UV detectors that can be grown on closely lattice-matched GaP substrates and can be provided with a cutoff wavelength tunable between 340nm-400nm. However there remains a need for photodiodes with a still lower cutoff wavelength. In this invention, a novel ultraviolet detector with cutoff wavelength tunable from 340nm-270nm is disclosed. ZnMgS alloy thin film with thickness thinner than its critical thickness of a structural transition is used as the active layer in this novel Schottky-barrier structure. Its response in the UV spectral region has an external quantum efficiency as high as 50%, a sharp cutoff and more than four orders in visible rejection power. Its response time is fast and dark current density is very low. In particular, a device with Mg composition of the active layer equals to about 57% offers a response curve closely matching to the erythemal action spectrum that describes human skin sensitivity to UV radiation. The achievement of solar-blind characteristics in this invention can also open up a novel approach for cost-effective flame detection system.
Technology Benefits
1. Cost effective
2. Tunable in cutoff wavelength
3. Fast response
4. Requiring no external power supply (photovoltaic mode)
5. High responsivity
6. Intrinsically having high discrimination against visible and infrared background or even the entire solar radiation (without the use of any filter)
7. Capable to offer a response curve closely matching to the erythemal action spectrum

Technology Application
- Build-in watch and sunglasses sensor for UV index reporting and UV exposure monitoring
- Components of novel fire safety equipment
- UV astronomy
- Practical applications for industry and scientific research such as UV curing, flame sensing and detectors for spectral analysis
Supplementary Information
Patent Number: US6610985B2
Application Number: US2001910041A
Inventor: Sou, Iam Keong | Wu, Chi Wai Marcus | Wong, Kam Sing | Wong, Ke Lun George
Priority Date: 23 Jul 2001
Priority Number: US6610985B2
Application Date: 23 Jul 2001
Publication Date: 26 Aug 2003
IPC Current: G01J000142
US Class: 250372
Assignee Applicant: The Hong Kong University of Science & Technology
Title: ZnMgS-based UV detectors
Usefulness: ZnMgS-based UV detectors
Summary: For detecting flame for fire safety, UV astronomy, etc. Also, for manufacturing metal-semiconductor-metal (MSM) device, Schottky diode structure, etc.
Novelty: Ultraviolet detector for fire safety, contains undoped ultraviolet active materials such as zinc, silicon, magnesium at predetermined proportion
Sub Category
Measurement Tool
Application Date
23 Jul 2001
Application No.
US 09/910041
Patent Information
US 6610985
ID No.
Hong Kong

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