Schottky barrier height enhancement on n-In0.53Ga0.47As

Abstract

Schottky barrier height enhancement on n-InGaAs is studied on structures with thin surface layers of different compositions. Counter-doped p+-InGaAs layers, as well as layers of n- and p-InP, n-GaAs, and n-InGaP of different thicknesses and dopant densities, respectively, were used to enhance the barrier. Titanium was used as a barrier metal to prepare Schottky diodes of different areas and the barrier height is analyzed by current-voltage measurements. It is observed that the barrier height enhancement by p+-InGaAs layers increases with the layer thickness and dopant density, respectively, and effective barrier heights up to 0.63–0.68 eV, i.e., higher values than previously reported, have been measured. The barrier height enhancement by counter-doped p+-InGaAs layers on n-InGaAs can be described by the two-carrier model. Schottky diodes with extremely low reverse current densities have been prepared, JR(1 V) =4.5×10−6 A/cm2. It is shown that lattice-matched InP surface layers can be used as an alternative to enhance the barrier height on n-InGaAs. The barrier height increases with the layer thickness up to φB=0.53–0.55 eV, i.e., up to values previously reported as barrier heights on thick n-InP. Additional barrier enhancement can be achieved by counter doping of the InP surface layer and barrier heights of 0.66 eV have been obtained by p-InP surface layers on n-InGaAs. On structures with barrier-enhanced n-GaAs layers, a remarkable decrease of the reverse current density is observed if the layer thickness is reduced to the critical layer thickness, but the barrier height is very low due to the small n-GaAs thickness. For structures with slightly lattice-mismatched n-InGaP layers (xGaP=0.11) measured barrier heights are similar to those for n-InP enhancement layers of the same thicknesses.