InGaAsN MSM photodetectors using RF-Sputtered ITO layers as transparent Schottky contacts

Abstract

The RF-sputtered ITO layers were used as the transparency contact layer of the MSM PDs. The plasma gas would alter the optical transmittance and the schottky barrier height between the ITO layer and InGaAsN absorption layer. Three kinds of plasma gases were studied including Ar, Ar/N₂, and Ar/O₂. The Schottky barrier heights were 0.510 eV, 0.572 eV, and 0.574 eV when using Ar, (Ar/N₂), and (Ar/O₂) as the plasma gas; besides, the optical transmittances were 92.56%, 93.12% and 96%, respectively. Although the ITO film sputtered in the Ar/O₂ ambient has highest transmittance and Schottky barrier height, the high resistivity limited the photocurrent of the photodetectors; it is almost three orders lower than the others. Consequently, using the Ar/N₂ as the plasma gas would be a suitable choice regarding the MSM photodetector application. The highest contrast ratio between photo-current and dark-current of the InGaAsN MSM photodetectors were 5, 25 and 12 (measured under 0.2V) using Ar, Ar/N₂, and Ar/O₂ as the plasma gases.