Metal/III-V Schottky barrier height tuning for the design of nonalloyed III-V field-effect transistor source/drain contacts

In this work, we introduce a novel nonalloyed contact structure for n-GaAs and n-In0.53Ga0.47As by using single metals in combination with a thin dielectric to tune the effective metal/III-V work function toward the conduction band edge. We reduced the effective Schottky barrier height (Phi(B,eff)) of Al/GaAs from 0.75 to 0.17 eV through the use of a thin atomic layer deposition Al2O3. Barrier height reduction was verified for a variety of metals (Y, Er, Al, Ti, and W) through direct measurements and deduced from increased diode current and reduced contact resistance. Similar results were observed on n-In0.53Ga0.47As. Two possible underlying mechanisms are discussed: one based on the formation of a dielectric dipole and the other based on the blocking of metal induced gap states. This structure has applications as a nonalloyed low resistance ohmic contact for III-V metal-oxide-semiconductor field-effect transistors (MOSFETs) or high electron mobility transistors (HEMTs), and as a near zero barrier height contact for III-V Schottky barrier field-effect transistors or diodes.