Modification of metal–InGaAs Schottky barrier behaviour by atomic layer deposition of ultra-thin Al2O3 interlayers

•Investigation of the modification of metal–InGaAs Schottky barrier (SB) behaviour•Improving metal–InGaAs interface by sulphur passivation and ultrathin interlayer•Examine the effect of low work function and high work function metals on SB•Different SB behaviours observed on both n-type InGaAs and p-type InGaAs•Metal/n-InGaAs interface is more strongly pinned than the metal/p-InGaAs interface.

The effect of inserting ultra-thin atomic layer deposited Al2O3 dielectric layers (1 nm and 2 nm thick) on the Schottky barrier behaviour for high (Pt) and low (Al) work function metals on n- and p-doped InGaAs substrates has been investigated. Rectifying behaviour was observed for the p-type substrates (both native oxide and sulphur passivated) for both the Al/p-InGaAs and Al/Al2O3/p-InGaAs contacts. The Pt contacts directly deposited on p-InGaAs displayed evidence of limited rectification which increased with Al2O3 interlayer thickness. Ohmic contacts were formed for both metals on n-InGaAs in the absence of an Al2O3 interlayer, regardless of surface passivation. However, limited rectifying behaviour was observed for both metals on the 2 nm Al2O3/n-InGaAs samples for the sulphur passivated InGaAs surface, indicating the importance of both surface passivation and the presence of an ultra-thin dielectric interlayer on the current–voltage characteristics displayed by these devices.