The optical transmittance of indium-tin-oxide (ITO) at a wavelength of 1.3 pm has been improved by adding forming gas (H2/N2) to the Ar sputtering gas. It is shown that the presence of H2 in the plasma decreases the carrier concentration in ITO, and increases the optical transmittance of a 320 nm-thick ITO film from 69.7% to 99.5%. The application of the high transmittance ITO to the fabrication of metal-semiconductor-metal (MSM) photodiodes on InAlAs/InGaAs heterostructures has resulted in an improvement of responsivity from 0.6 A/W to 0.76 A/W. This is double the responsivity of 0.39 A/W obtained for Ti/Au detectors. A 3-dB bandwidth of 6 GHz was obtained for the high transparency ITO device with 3 μm fingers and gaps and with an area of 50 × 50 μm2.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering