Papers by kunal bhatnagar
Physical Review B, 2017
The electronic properties of epitaxial oxide thin films grown on compound semiconductors are larg... more The electronic properties of epitaxial oxide thin films grown on compound semiconductors are largely determined by the interfacial atomic structure, as well as the thermodynamic conditions during synthesis. Ferroelectric polarization and Fermi-level pinning in SrTiO 3 films have been attributed to the presence of oxygen vacancies at the oxide/semiconductor interface. Here, we present scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) analysis of GaAs films grown on SrTiO 3 combined with first-principles calculations to determine the atomic and electronic structures of the SrTiO 3 /GaAs interfaces. An atomically abrupt SrO/As interface is observed and the interfacial SrO layer is found to be O-deficient. Firstprinciples density functional theory (DFT) calculations show SrO/Ga and Sr/As interfaces are favorable under O-rich and O-poor conditions, respectively. SrO/Ga interface is reconstructed via the formation of Ga-Ga dimers while Sr/As interface is abrupt and consistent with the experiment. DFT calculations further reveal that intrinsic two-dimensional electron gas (2DEG) forms in both SrO/Ga and Sr/As interfaces and the Fermi level is pinned to the localized 2DEG states. Interfacial O vacancies can enhance the 2DEG density while it is possible for Ga/As vacancies to unpin the Fermi level from the 2DEG states.
The impact of scaling on off-state current of p-in diodes is studied. A submicron p-in diode exhi... more The impact of scaling on off-state current of p-in diodes is studied. A submicron p-in diode exhibits a dominating surface component of leakage current. Variation in i-layer thickness has an impact on bulk leakage. Bulk leakage scales with cross-sectional area of the diode and surface leakage has been controlled using surface treatments to give ultra low leakage currents of 210 fA for a device of cross sectional area of 0.44 µm 2. Devices of 100 nm i-layer thickness show an average bulk and surface current densities of 100 mA/cm 2 and 150 fA/µm, respectively.
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Papers by kunal bhatnagar