Electrical characteristics and deep level traps study of Au/ZnO:H Schottky diodes

Abstract

The electrical characteristics and the deep level traps of Au Schottky contacts on ZnO:H films have been investigated by temperature-dependent current–voltage (I–V) and deep level transient spectroscopy (DLTS) measurements. The films were deposited with the DC-sputtering, varying the H flow rate in the Ar/H sputtering gas, so that the hydrogen per volume concentration [H2] was 0%, 20%, 33.3%, 50% and 66.6%. We found that for the Schottky diodes with [H2]=33.3% thermionic emission is the dominant current transport process at low forward voltage, taking into consideration the lateral fluctuations of the barrier height described by a Gaussian distribution model. The domination of trap-assisted current transport mechanisms is possible in the diodes with [H2]=0%, 20%, 50% and 66.6%. DLTS spectra revealed two electron traps, with activation energies of 0.29 and 0.21eV, often observed in ZnO and related to intrinsic defects. The trap concentrations are significantly lower in the 33.3% H2 diodes compared to the 0% H2 ones, indicating an interaction of these traps with hydrogen.