Electron Tunneling into KTaO3Schottky Barrier Junctions

Electron tunneling techniques have been used to examine the characteristics of current ($I$) vs voltage ($V$) in degenerate $n$-type KTa${\mathrm{O}}_3$ Schottky barriers at 1 °K. The $\frac{d^{2}V}{d{I}^2}$-vs-$V$ curve exhibits structure at each of the four LO modes in KTa${\mathrm{O}}_3$: 22.5, 34, 51.5, and 102.5 mV. Several two-phonon peaks were also seen and identified as 51.5 + 102.5 = 154-mV and 2 × 102.5 = 205-mV combinations. The almost antisymmetric nature of the phonon-induced structure about zero bias indicates that it is caused by the inelastic interaction of the tunneling electrons with phonons in the barrier. In addition, the maximum in the differential resistance $\frac{\mathrm{dV}}{\mathrm{dI}}$ occurs at a bias equal to the Fermi level of the semiconductor, and an effective conduction-band mass $m^{*}=0.\mathrm{}5m_0$ of the free carriers has been determined.