Acceptor-like electron traps control effective barrier for ultrahigh vacuum-cleaved and laser-annealed Al/InP

Abstract

We analyze the temperature dependence of the current and capacitance responses for Al contacts on UHV-cleaved (110) n-InP. We compare pulse-laser-annealed contacts to unannealed contacts formed concurrently on the opposite half of each freshly-cleaved InP surface. Acceptor-like electron traps lying 0.10 eV below the conduction band (a level sometimes ascribed to donors in the unified defect model) dominate electronic behavior. These traps occur in an interfacial layer whose thickness is reduced from ∼160 to ∼34 Å by laser annealing. Both laser-pulsed and unannealed contacts have a 0.22 eV barrier height. The fact that the 0.5 eV barrier of Al reported on treated InP also decreases to 0.22 eV upon heating suggests that the barrier stabilizes between two states with a stable, reproducible concentration ratio.