Filterless Selectively Sensitive Photodetector
Filterless Selectively Sensitive Photodetectors for Effective Monitoring UV and Visible Radiation
Tech Area / Field
- INF-SIG/Sensors and Signal Processing/Information and Communications
- INF-ELE/Microelectronics and Optoelectronics/Information and Communications
- INS-DET/Detection Devices/Instrumentation
3 Approved without Funding
National Polytechnical University of Armenia, Armenia, Yerevan
- University of Ottawa / Centre for Research in Photonics, Canada, ON, Ottawa\nSiemens Canada Limited, Canada, ON, Mississauga\nConcordia University, Canada, QC, Montreal\nD & Assoc, USA, CA, Los-Angeles\nFachhochshule Aachen, Germany, Jülich\nSheffield Hallam University / Materials and Engineering Research Institute, UK, Shiffield\nHelsinki University of Technology / Metrology Research Institute, Finland, Helsinki\nNational Technical University of Athens / Department of Electrical Engineering and Computer Science, Greece, Athens\nTechnische Universität Darmstadt / Institut fuer Hochfrequenztechnik, Germany, Darmstadt
Project summaryThe aim of the project is to develop a new type of a monolithic solid-state selective filterless photodetector on silicon base, capable of differentially registering separate narrow bands of ultra-violet (UV) radiation without the use of complex and expensive systems of optical light filters. The resolution of these photodetectors is as high as ~1nm. They are inexpensive and compact.
Recently, considering the demands of medicine, ecology, biotechnology and jam-resistant UV location, the necessity of the creation of selective photo converters for the UV-areas of solar spectrum has particularly increased. The new photo converters are capable of registering narrow frequency bands [1-3] against the background of powerful visible and IR radiations. These narrow frequency bands are weak but have strong influence on vital ability of a man.
In this connection the creation of selectively-sensitive along the wavelength of the radiation photodetectors is very important and actual. These photodetectors will replace the expensive and ineffective optical filters which are used for extracting the necessary spectral channel from the integral flux of radiation.
So far the most commonly used types of UV photo converters have been silicon photo detectors with potential barriers. Commercial Si-photo diodes have spectral domain of photo sensitivity 0,2 - 1,1 microns, their maximal spectral sensitivity being in the IR-area. That results in big mistakes in measurements, since the frequently weak UV signal is measured against the background of powerful visible and IR radiations, and the UV light filters, though they cut off the visible area, have high gating in the IR area . The existing solid-state UV photo detectors on the base of SiC, GaN, GaP and other compounds do not provide the required selectivity of registration. They are incompatible with the production engineering of integrated circuits and are expensive in manufacturing.
The research  describes Si and SiC-based multichannel selective filterless photodetectors for UV area of the spectrum, which consist of a number of photodiodes with different base thickness. To maintain the accuracy of measurements in these photodetectors, it is necessary to create absolutely identical conditions of radiation influence all along the stepped structure. This complicates their application, especially at low radiation intensities. Besides, the manufacturing of such structures needs large material consumption.
This project proposes a new solution to the selectivity problem of photo converters for UV and visible areas of the spectrum. These photo converters will help to raise the accuracy of measurements without the use of expensive filters and to reduce the material consumption in photo detector manufacturing.
The suggested photodetector is a monolithic solid-state structure based on two oppositely directed potential barriers on each side of the high-resistance thin base. The potential barriers are generated by the contact of metal - semiconductor (Schottky barrier) and n-р junction. Silicon is used for the base area. The concentration of the charge carriers of the base area is selected so that to provide the coupling of the areas of the volume charges of the two junctions. The photodetector being illuminated oppositely directed photocurrents are generated in the field of volume charges of both barriers at the expense of absorption. These oppositely directed photocurrents define the resulting photocurrent of the structure. The latter depends on the balance between the absorptance and the widths of the areas of the volume charges of junctions . The change of the external voltage to V changes that balance. The selective registration of the UV radiation by the photodetector is provided by the dependence of the photocurrent on the impressed bias voltage V and on the received data processing. During data processing the whole spectrum of the radiation can be broken into narrow spectral bands and the contribution of each spectral band of the radiation in the photo response can be allocated by selecting the step of the external voltage change V.
The special feature of the suggested photodetector is the existence of the inversion of the spectral photocurrent sign, the linear dependence of the inversion point on the voltage and the independence of the spectral photocurrent from the heterogeneity of the radiation incident upon the surface of the photo detector .
These features provide high accuracy of measurements and enlarge the possibilities of application of such structures, for example, as a multiple-wavelenght-channel detector for spectrometers. By estimation, the suggested photodetectors provide spectral resolution ~1 nm at the threshold sensitivity 10-14 Вт. Hz -1/2.
The principle of operation of the suggested photodetector is rather universal and it can be applied for the manufacturing of photodetectors on the base of various materials. The width of the band-gap of the semiconductor defines the spectral domain of the radiation registration, and the double-barrier structure - the spectral resolution.
Mathematical modelling of electronic processes in solid-state double-barrier structures with thin base for the purpose of the creation of inexpensive and compact selectively-sensitive filterless photo detectors. Substantiation of their optimal designs and manufacturing methods.
Project development and results of researches can have the following applications:
- Ecology - the problem of the "ozone gap", the detection of environment pollution;
- Medicine - physiotherapy, blood autotransfusion, sunlight irradiation of people;
- Disinfection of water, air, clothes, tools and foodstuff;
- Astronavigation and ultra-violet location (in addition to infra-red location);
- Astronomy - getting the information about physical processes in space projects, about their UVR;
- Science of materials - definition of substance makeup and of the electronic structure of elements;
- Nuclear physics and power engineering - registration of nuclear particles with the help of scintillators;
- Defectoscopy, criminalistics, art criticism (fluorimetric analysis under the influence of UVR);
Agriculture - hotbed and hothouse agrotechnology;
Biotechnology - synthesis of vitamins D2 and D3, investigation nano – bio systems;
After the project close-out it is planned to receive selectively-sensitive photodetectors for the range of wavelengths from 0,2 to 0,66 microns with the spectral sensitivity controlled by the external voltage and with the resolution ~1nm. At the external voltage within -0,5 up to 0,5 W the dark currents of photodetectors will not exceed 10-13 А/сm2, and the speed of response will be not more than 10-10 sec. It is also planned to establish economically defensible experimental manufacture of developed photodetectors, the estimated cost of which will not exceed the cost of traditional photodetectors; and that points to their doubtless commercial value.
Foreign collaborators will participate in the research of photo-electric features and parameters of photodetector structures, as well as in the commercialization of the received results and their promotion in the market. The foreign collaborators will also take part in joint seminars and conferences, as well as in the problem discussions and the exchange of information received in the course of the project completion.
Foreign collaborators will participate in experiments on investigating the photoelectric and physical properties of two-barrier structures. They may also assist the commercialization of the obtained results and their advance to the market. The role of foreign collaborators is also to discuss the problems and exchange the information, obtained during the implementation process of the Project to take part in scientific seminars and conferences, organized by the executor.
Realization of the project will permit to solve a number of problems answering the ISTC purposes:
- To re-orientate the highly qualified group of scientists, engineers and technical workers, who used to work in the sphere of arms for peace settlement,
- To provide scientists with alternative peace work,
- To further integrate the scientists working in the sphere of arms into the international community of scientists and to develop traditional cooperation with the organizations and universities of the CIS,
- To develop high technologies in Armenia.
The manager and the group of scientists working on the project are leading experts in this sphere. They have numerous publications, as well as inventors’ certificates. The work planned on the project is based on the many years' experience of the group in the field of the development of microelectronic and optoelectronic means and devices. All that points to the opportunity of getting positive results and succeeding in the project.
- T. V. Blank and Yu. A. Goldberg, Semiconductor Photoelectric Converters for the Ultraviolet Region of the Spectrum. Semiconductors, V. 37, Issue 9, 2003, pp. 999-1030.
- K. Jokela, L. Ylianttila, R. Visuri, K. Leszczynski, P. Kдrhд, and E. Ikonen, “Intercomparison of lamp and detector-based UV-irradiance scales for solar UV radiometry,” J. Geophys. Res. 105, 4821-4827 (2000)
- Schöning, M.J.; Lüth, H., Novel concepts for silicon-based biosensors, Physica Status Solidi A 185 (1), (2001) 65-77.
- Nader M. Kalkhoran, Fereydoon Namavar. Multi – Band Spectroscopic Photodetector Array. Patent US005671914A.
- Khudaverdyan S.Kh., Dokholyan J.G., Kocharyan A.A., Kechiyantz A.M. and Khudaverdyan D.S. On functional potentiality of photodiode structures with a high-resistance layer //. ELSEVIER, Solid State Electronics. V. 49, Issue 4, 2005, p. 634-639.