Ag/Ai schottky contacts on n-InP

Abstract

Schottky contacts have been fabricated onn- InP using a Ag/Al/InP configuration where the Ag and Al thicknesses are 1000 and 40-50A, respectively. Diodes fabricated on InP substrates withn ≈ 7 x 1016 cm-3, have effective barrier heights, Obeff, of 0.4 eV and reverse bias leakage current densities of >4 A/cm2 atVr = - 3V. Appropriate heat treating at temperatures between 400–500° C raises barrier heights by as much as 0.25 eV, resulting in Obeff ≈ 0.65 eV and reverse bias leakage current densities less than 0.002 A/cm2. Diode characteristics are found to vary dramatically with different surface preparations prior to metallization; results of x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) depth profiling studies indicate that native oxides which are predominantly InPO4 produce superior contacts and that aluminum first reacts with the native oxide and then migrates through the silver to the free metal surface which results in the dramatic improvements observed upon annealing.