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Oxide Semiconductors

Complex oxide semiconductors for electronic applications


Complex oxide semiconductors for electronic applicationsThe development of epitaxial oxide structures with unprecedented high electron densities has the potential to create a new class of extreme power-density electronics for communications and energy applications. The objective of the project is to enable new electronic and plasmonic devices through the control of extreme-density, two-dimensional electron gases at polar oxide interfaces, engineering the band separation at oxide interfaces and innovative approaches to increase electron mobility and carrier velocities. The device research program is underpinned by research aimed at advancing oxide materials physics to address challenges such as intrinsically low carrier mobilities.
The SrTiO3/GdTiO3 (STO/GTO) interface shows to have an extremely high sheet charge density of 3e14 cm-2, equivalent to the 1/2 electron per interface unit cell required to compensate the polar discontinuity at the interface. Such interfacial 2-dimentional electron gases (2DEGs) can be used to design innovative oxide electronic devices, analogous to heterostructure field effect transistors (HFETs) based on conventional semiconductors such as GaAs and GaN, but with an order of magnitude higher charge density. Oxide materials also provide the advantage of higher breakdown strength due to the higher dielectric constant. The maximum sheet charge density that can be modulated, based on the relationship qns= εrε0FBR(where ns is the sheet carrier density, εris the relative permittivity, and FBRis the breakdown field), is an order of magnitude higher in STO than other traditional semiconductors such as Si, GaAs, or GaN, due to the higher dielectric constant (~300) of STO.
We are the first to demonstrate STO/GTO HFET, with the first results of direct current modulation in the SrTiO3/GdTiO3 system and the highest recorded charge modulation of up to 6e13 electrons/cm2for any semiconductor material system.
PUBLICATIONS:

1) P. Moetakef, T.A. Cain, D.G. Ouellette, J. Y. Zhang, D. O. Klenov, A. Janotti, C.G. Van de Walle, S. Rajan, S. J. Allen, and S. Stemmer, "Electrostatic carrier doping of GdTiO3/SrTiO3 interfaces", Applied Physics Letters, 99, 232116 (2011).

2) M. Boucherit, O. F. Shoron, T. A. Cain, C.A. Jackson, S. Stemmer, and S. Rajan, "Extreme charge density SrTiO3/GdTiO3 heterostructure field effect transistors", Applied Physics Letters, 102, 242909(2013).

3) J. Son ,S. Rajan, S. Stemmer, and S. James Allen ," A heterojunction modulation-doped Mott transistor", Journal of Applied Physics, 110, 084503 (2011).