1.09-eV Schottky barrier height of nearly ideal Pt/Au contacts directly deposited on <i>n</i>- and <i>p</i>+<i>n</i>-Al0.48In0.52As layers

Abstract

Pt/Au Schottky contacts on AlInAs lattice-matched to InP have been fabricated using effective cleaning of the semiconductor surface with low-energy (30 eV) Ar+ ions prior to the metal deposition. A short-time annealing of the contacts at moderate elevated temperatures in the range of 230 to 430 °C was employed in order to eliminate eventual postbombardment defects. Subsequently, an increase of the effective Schottky barrier height from 0.85 to 1.09 eV was observed. This improvement is probably due to the heteroalignment between PtAs2 and AlAs phases which easily appears if intimate contacts are considered. Conventionally prepared wafers (without ion-beam treatment) exhibit a barrier height of 0.82 eV which remains unchanged during annealing. The initial breakdown voltage in ion-etched samples rises from −18 to −28 V and the reverse current density at −10 V diminishes by more than two orders to less than 8×10−7 A cm−2. An ideality factor n very close to unity was obtained from the slope of forward current-voltage characteristics of contacts to homogeneously and shallow Zn-doped substrates.