Effect of Ge interface control layer on the interfacial and electrical properties of TaYO_x thin films on GaAs substrates

Effects of a Ge interface control layer on the electrical properties of RF sputter-deposited TaYO_x on n-GaAs substrates are studied in detail. It is found that the incorporation of an ultrathin Ge layer in between TaYO_x and GaAs substrate improve various electrical parameters such as interface state density, border trap density, frequency dispersion, leakage current density and flat-band shift thereby improving capacitor performance. The trapping of charge carriers in GaAs MOS capacitors during constant voltage stress has also been studied and the increase in gate leakage current observed during electrical stress is estimated and explained by taking into account the build up of trap charges and stress induced trap generation. The cross-section of traps is also estimated to be in the range of 10⁻¹⁸ cm². Such a small value for the capture cross-section implies that the generated traps are neutral centers which are probably responsible for trap-assisted tunneling during voltage stressing.