Defect-induced Schottky barrier height modification by pulsed laser melting of GaAs

Abstract

A pulsed XeCl excimer laser (λ=308 nm) is used to melt n- and p-type GaAs samples. Melt-induced defects shift the surface Fermi level to a new pinning position at 0.58±0.04 eV below the conduction-band minimum for both n- and p-type samples. The Schottky barrier height of Au, deposited on the GaAs after laser irradiation, is increased by 0.38 eV (from 0.43 to 0.81 eV) for p-type, and decreased by 0.30 eV (from 0.84 to 0.54 eV) for n-type samples. In the post-melted GaAs near-surface region, four deep levels are found using deep level transient spectroscopy. The observation of minority-carrier traps in the Schottky diode structures suggests the existence of minority-carrier source. We speculate a compensated region forms near the GaAs surface. A bulk Fermi level stabilization model is used to explain the changes observed in the Schottky barrier heights.