Electron Tunneling and Band Structure of SrTiO3and KTaO3

Abstract

The tunneling characteristics of In-SrTi${\mathrm{O}}_3$:Nb and In-KTa${\mathrm{O}}_3$:Ca Schottky barriers have been studied at different temperatures and for different concentrations of carriers. The plot of differential resistivity shows a distinct peak at forward biases which is attributed to the critical point in the density of states at the bottom of the semiconductor conduction band. From the position of the peak, the density-of-states effective masses $m_d$ have been found to be $1.3m_0$ in SrTi${\mathrm{O}}_3$ and $0.69m_0$ in KTa${\mathrm{O}}_3$. In combination with magnetoresistance data, the widths of the conduction bands have been determined. The over-all widths of the $d$ bands are about 3.4 and 6.8 eV for SrTi${\mathrm{O}}_3$ and KTa${\mathrm{O}}_3$, respectively. Finally, in the theoretical part, the conduction-band structure of transition-metal perovskites is discussed.