Ashkhen Yesayan

	Name:		ASHKHEN YESAYAN
	Title:		Sci. worker of Laboratory of Physics of Semiconductor Materials and Devices, Yerevan State University , Armenia
	Telephone/Fax:		+374 10 578382
	E-mail:		ashye@ysu.am
Graduate:		Dept. of Radiophysic, Yerevan State University , Armenia , Physics of Semiconductors and Insulators, 1994
Main Research Interests:		Semiconductor physics, Low-dimensional systems, Nanodevices, Optoelectronic Devices, physical and optical properties of the semiconductor-liquid interfaces
Subsidiary Research Interests:		2D p-n junctions, 2D IPG FETs
Research Experience:		Governmental grant of Ministry of Science and Education of Armenia
Main Publications: 1. S.G.Petrosyan, A.E.Yesayan, D.Reuter and A.D.Wieck, The linearly graded two-dimensional p-n-junction, Appl. Phys.Letters, v.84, N.17, p.3313 (2004). 2. A. E. Yesayan, V.M.Aroutionian, S.G. Petrosyan, Multiple quantum well photodiode with lateral p-n-junctions, Thin Solid Films, v.451-452, pp.389-392 (2004). 3. A.Sh. Achoyan , A.E. Yesayan , E.M. Kazaryan and S.G.Petrosyan, Two-dimensional p-n-junction under Eauilibrium Conditions, Semiconductors, v.36, N.8, pp.903-907 (2002). 4. V.M.Aroutiounian, V.A.Gevorkyan, A.E.Yesayan and S.G.Petrosyan, Photo-emf in Parabolic Graded-Gap Semiconductors, Phys. Stat.Sol. (a), v. 184, N.2, pp.433-436 (2001). 5. S.G.Petrosyan, A.E.Yesayan and E.S.Yuzbashian, Photoconductivity and the Photo-Hall effect in Inhomogeneous Semiconductor Alloys, J.Phys.: Condens. Matter, v.8, pp.5707-5715 (1996).
Directions of Research: Two-dimensional electron gas FETs We consider 2DEG junction FET in which 2DHGs on both sides of 2DEG serves as gates. The channel depletion and pinch-off mechanisms are established for 2D-JFET. For the narrow channels the changes in lateral electron density induced by both gates can overlap reducing the overall density of free electrons in channel. This is a main difference from ordinary JFET, where the gate depletes the channel laterally only through a reduction in effective width, without affecting the carrier density in the middle of the channel at low gate voltages. First we suggest constant mobility model which provides an accurate description of 2DEG JFET with low pinch-off voltage and an approximate description of 2DEG JFET with higher pinch-off voltages. And then we developed a complete velocity saturation model which accurately describes high pinch-off voltage devices. Both models provide analytical expressions for the current voltage characteristics, and are quite suitable for parameter acquisition. Multiple Quantum Well Photodiode with lateral 2D p-n-junctions The structure for the Multiple Quantum Well Photodiode with Lateral Two-dimensional p-n-junctions has been developed. We have done the calculations of the responsivity and its spectral dependence of such photodiode under the steady-state illumination. It's shown that the responsivity increases linearly with applied voltage and at moderate voltages can exceed 1A/W. Two-dimensional p-n-junction For the first time the idea of a Two-dimensional p-n-junction was proposed and under equilibrium conditions the potential distribution were determined. The current-voltage and capacitance-voltage characteristics of such contact have been derived. The photocurrent versus from the position of a light strip on the photosensitive surface of such junctions has been calculated, too. The low frequency capacitance of 2D p-n-junction has been calculated. The results are in a very good agreement with the experiments. The Photo-emf in parabolic graded-gap semiconductors has been studied.
News: Conferences § 7^th Young International Young Scientists Conference on Optics SPO-2006, Kiev , Ukraine , 2006. § 8^th International Conference on Nanometer-Scale Science and Technology NANO-8, Venice , Italy 2004. § Workshop on Quantum Systems Out of Equilibrium, ICTP, Trieste , Italy 2004, § Spring College on Science at the Nanoscale, ICTP, Trieste , Italy 2004. A.E.Yesayan, S.G.Petrosyan, Field Effect Transistor on 2DEG, Vestnik RAU, v 1,pp. 63-67 (2005). S.G.Petrosyan, A.E.Yesayan, D.Reuter and A.D.Wieck, The linearly graded two-dimensional p-n-junction, Appl. Phys.Letters, v.84, N.17, p.3313 (2004). E. Yesayan, V.M.Aroutionian, S.G. Petrosyan, Multiple quantum well photodiode with lateral p-n-junctions, Thin Solid Films, v.451-452, pp.389-392 (2004).