Abstract
We demonstrate the integration of a two-dimensional electron gas (2DEG) oxide structure composed of $\mathrm{LaTi}{\mathrm{O}}_{3}/\mathrm{SrTi}{\mathrm{O}}_{3}$ (LTO/STO) on undoped Si(001) that possesses the attractive attributes of high charge density from the oxide and high mobility of silicon. Key to this approach is modification of the oxygen content at the STO-Si interface, which tunes the band alignment and induces electron carriers to move from the oxide 2DEG to form a 2DEG in the silicon substrate. As a consequence, the overall mobility of the heterostructure increases by two orders of magnitude compared to that in the oxide 2DEG to up to $100\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{2}{\mathrm{V}}^{\ensuremath{-}1}{\mathrm{s}}^{\ensuremath{-}1}$ at room temperature, with a carrier density of $\ensuremath{\sim}1\ifmmode\times\else\texttimes\fi{}{10}^{13}\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}2}$. This approach can be applied to technologies that require both high carrier and high carrier mobility for applications in plasmonics and high power electronics.
Highlights
The discovery of oxide two-dimensional electron gas (2DEG) systems such as LaAlO3/SrTiO3 (LAO/STO) [1] and RTiO3/SrTiO3 (RTO/STO) [2,3,4,5,6], where R is a trivalent rare earth ion, has opened a new field of physics for high density charge modulation [7] and the development of devices built from oxide heterostructures
We show how a high carrier density and high mobility can be achieved through the integration of an oxide heterostructure with a semiconductor
We have demonstrated an approach to increase the room temperature oxide mobility in STO-based 2DEG heterostructures integrated on Si in order to realize high (a) carrier concentration and high mobility structures for applications based on a scalable semiconductor platform
Summary
The discovery of oxide two-dimensional electron gas (2DEG) systems such as LaAlO3/SrTiO3 (LAO/STO) [1] and RTiO3/SrTiO3 (RTO/STO) [2,3,4,5,6], where R is a trivalent rare earth ion, has opened a new field of physics for high density charge modulation [7] and the development of devices built from oxide heterostructures. We show using x-ray photoemission (XPS) studies that a staggered conduction band alignment between the STO and Si creates a barrier to electrons, trapping the charge to the STO layer and resulting in low STO-like mobilities. Firstprinciples theory predicts that the addition of a monolayer of oxygen atoms at an STO-Si interface creates a dipole that moves the STO conduction band up by ∼0.5 eV [14]. The consequence of this minimized conduction band offset (CBO) between STO and Si is a dramatic increase of the room temperature oxide mobility in oxide 2DEG heterostructures on Si, improving from ∼1 cm2V−1s−1 in the as-grown samples. To change the band offset, we modify the oxygen content at the interface, which is predicted by theory to result in a 0.5 eV increase of the STO-Si band offset
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