Improvement in Schottky diode characteristics of metal-In0.52 Al0.48As contact using an in situ photochemical etching and surface passivation process

HBr and H₂S gases were used together with a 172 nm excimer lamp and a deep UV-lamp for photochemical etching and surface passivation of the InGaAs/InAlAs material system. Schottky diodes were fabricated on n-In_0.52Al_0.48As by electron beam evaporation of Mo/Ti/Pt/Au with the consequent alloying. AES and XPS measurements of the passivated InAlAs surface reveal that the photochemically generated S*-radicals are capable of removing In-O and As-O bonds from the surface and replacing them with In-S and As-S bonds. The reverse bias leakage current of the surface passivated diodes were reduced by 3 orders of magnitude compared to diodes with an unpassivated surface. We obtained an effective barrier height of 0.79 eV and an ideality factor of 1.03, for the fabricated diodes after surface passivation