Schottky Barrier Height Reduction at Interface Between GZO Transparent Electrode and InP/InGaAs Structure by Zinc Driven-in Step and Nickel Oxide Insertion

In this letter, we report the characteristics of transparent Ga-doped ZnO (GZO) electrodes contacted to the InP/InGaAs epitaxial structure both with and without a NiO_x inserting layer. The GZO films deposited onto the p-InP/InGaAs structure by both radio-frequency sputtering and plasma-mode atomic layer deposition always yield Schottky contact characteristics. The barrier height improvement at the n-GZO/p-InP interface is proposed using dual zinc driven-in steps and a NiO_x insertion layer to realize ohmic characteristics. The high zinc concentration (5-8 × 10¹⁸ cm^-3) is first obtained in the surface of the p-InP window layer via the dual zinc driven-in steps. By inserting a NiO_x layer between the GZO and Au/Cr contact films, the Au/Cr/GZO/NiO_x contact pad for zinc driven-in p-InP window layer and the postannealing process of 430 °C for 180 s exhibits a good ohmic contact behavior and a low specific contact resistance of 3.07 × 10^-4 Ωcm².