Titanium Dioxide Based Photodiodes
Fabrication of Ultraviolet TiO2 Photodiodes and Study of their Properties
Tech Area / Field
- INS-DET/Detection Devices/Instrumentation
3 Approved without Funding
State Research and Design Institute of Rare-Metal Industry, Russia, Moscow
- NPO Orion, Russia, Moscow\nOrion Research-And-Production Association “ORION” “RD&P Center”, Russia, Moscow
- University of Limerick, Ireland, Limerick\nUniversity of Delaware / Department of Materials Science and Engineering, USA, DE, Newark
Project summaryThe Project aim. The aim of this project is applied research and development of the laboratory technology of high quality and cheap photodiodes (PD) on the base of TiO2 for the ultraviolet range. The photodiodes should be Sсhottky type as well as ones with p/n transitions.
Current status. The world production of titanium dioxide exceeds 5.0 million tons a year. It is used as a pigment in a paint-varnish industry, in catalysts and so on. However recently, in the first time for the electronic industry, the commercial output has been organized on the base of this material, namely the production of photodiodes for the ultraviolet range of spectrum (solar-blind). These photodiodes have a comparatively low cost (from 13 up to 45 £ for various types). But it has low device parameters, particularly a high photoresponse time (up to several hundreds of millisecond depending on light intensity), a high dark current (30 pA at 0.01 V), and a low quantum efficiency (less than 0.02 A/W). The whole market of photodetectors is estimated in $10 billions.
The project’ influence on progress in this area. As a result of the project, the possibility of production of a competitive commercial product will be created. The possibility of formation of TiO2 layers with transport and photoelectric properties yield to nothing traditional semiconductor materials in this respect will be also demonstrated. This, in turn, gives a possibility of a more wide use of the material in the electronic and microelectronic industry.
The participants’ expertise. The team of the project has a considerable experience in development, manufacturing and study of properties of various type’s photodetectors as well as of integral circuits with MOS- and CMOS- technologies. The team has also a great experience in a growth of titanium dioxide layers with technique of a RF magnetron sputtering and study of its properties. The results of these investigations were regularly published in leading journals and presented at conferences.
Expected results and their application. As a result of the project fulfillment it is assumed, at conservation of the photodiodes low cost, to improve considerably TiO2 photodiode’s parameters, namely a sensitivity (not less than 0.3 A/W in a spectrum maximum) as well as the values of reverse currents, detectivity and speed of response. Comparatively to techniques of MBE and CVD that are used ordinary for photodiodes manufacturing, the technique of magnetron sputtering is more economical, in particular due to a possibility the device structures formation on a large area. Thus, one can suppose the cost price of photodiodes manufacturing will not exceed $10. The results of this work can be also used for fabrication of other types of devices, such as solar cells, gas sensors, catalysts and photocatalysts, when the high-quality p/n diode structures are demanded.
Meeting the ISTC goals and objectives. This project will provide its participants (weapon scientists) with an opportunity to redirect their activity to civil need elaborations. The project will assist Russian scientists to integrate into international scientific community, and to perform joint investigations in science – capacious area of modern microelectronics. Project is directed on the development of market – oriented economy – benefit technology responsive to civil needs.
Scope of activities. The following main activities will be carried out in frames of this project:
- Fabrication of n- and p-types TiO2 layers with a low resistivity
- Fabrication and study of properties of photosensitive n- and p-types TiO2 layers
- Creation of photodiode device structures with a Schottky-barrier
- Fabrication and study of properties of photodiode device structures with a p/n junction
- Study of the influence of a substrate material and a quality of the surface treatment on the properties of TiO2 layers and device structures
- Optimization of technology parameters of photodiode structure manufacturing
- Prepared TiO2 layers and photodiode device structures will be investigated with techniques of x-ray diffraction, electron and atomic force microscopies, deep level transient spectroscopy, optical spectroscopy (IR, VIS, UV), measurements of impedances, photosensitivity spectra and photoresponse times.
Role of Foreign Collaborators. Prof. Shah (University of Delaware, USA) and Prof. Arshak (University of Limerick, Ireland) have expressed their wish to become Collaborators of this Project. It is supposed the mutual discussions with the collaborators during the project fulfillment as well as the analyze of it’s results. The joint publications in scientific journals and the results presentations at international conferences is also planed. Besides, it is expected the help of collaborators in some experimental works. In particular, Prof. I. Shah will ensure a help with X-ray Photoelectron Spectroscopy measurements, and Prof. K. Arshak agrees to lead mutual impedance investigations and device radiation stability measurements.
Technical approach and methodology. The novelty of this project includes using the technique of RF magnetron sputtering instead of the zol-gel method for manufacturing of TiO2 layers for photodiodes with Schottky-barriers. It will ensure the considerable improvement of the photodiodes quality. It is well known, and our experience also shows, that the magnetron sputtering ensures making the high quality epitaxial TiO2 layers with a good crystal structure and a low concentration of defect centers. In turn, it leads to increase of charge carriers mobility and life time. As a result of it, the Schottky diodes parameters should be considerably improved.
Besides that, an additional improvement of photodiodes parameters should be achieved due to using the magnetron sputtering for manufacturing of device layers with p/n junction. In particularly, we suppose to use the results of a recently published work (S. D. Yoon, C. Vittoria, and V. G. Harris, J. Phys.: Cond. Mat. 20, 195206 (2008)) where the high-conductive p-type TiO2 layers were firstly created due to doping the oxide with Fe impurity. Now, any information about p/n device structures on the base of TiO2 is practically absent.