Temperature-dependent Fowler-Nordheim tunneling and a composition effect in anodized Al-Al2O2-Au diodes -: art. no. 104505

Current-voltage (I-V) curves of Al-Al2O3-Au diodes with anodized Al2O3 thicknesses between 12 and 54 nm have been measured between 100 and 320 K. Diodes are rectifying at 300 K. There is a marked decrease in rectification of I-V curves as temperature decreases from 300 to 100 K. Part of the decrease is due to a decrease in current when Au is positive (applied voltage V-A > 0 V); part of the decrease is due to an increase in current for V-A < 0 V as temperature decreases. A reversal of the rectification direction has been observed at 100 K. I-V curves for increasing V-A > 0 V are affected by the polarization of the diode by a negative voltage. I-V curves for decreasing VA are independent of previous history and are due to Fowler-Nordheim tunneling, J=CF2 exp(-B/F). Values of B and C are temperature dependent. B is used to obtain an effective barrier height for tunneling, E phi(.) phi(E) increases from similar to 1.5 to similar to 2.5 eV as temperature decreases from 300 to 100 K for V-A > 0 V. For V-A < 0 V, phi(E) similar to 2.3 eV at 100 K and increases to similar to 2.8 eV at 160 K, except for the diode with 12 nm of Al2O3. There is a relation between B and C In C=r+sB, where r and s are constants, which is analogous to a compensation effect or Meyer-Neldel relation for data that obey an Arrhenius equation. A model is proposed in which the tunnel barrier is determined by an impurity band in Al2O3. (c) 2005 American Institute of Physics.