GaN Photodetectors with Transparent Indium Tin Oxide Electrodes

Abstract

Sputtering indium tin oxide (ITO) and e-beam ITO films deposited onto GaN as transparent electrodes for applications in metal–semiconductor–metal (MSM) photodetectors were fabricated and reported. The transmittances of 1000 Å-thick sputtering-ITO and e-beam ITO films were 78% and 67%, respectively, at a wavelength of 350 nm. The variation in the transmittance of the sputtering ITO films was not dependent on film thickness. The estimated effective barrier heights of the sputtering ITO and e-beam ITO films to GaN were 0.46 and 0.95 eV, respectively. This difference in barrier height originates from the formation of InGaN at the interface of ITO/GaN. Finally, GaN MSM photodetectors were fabricated using e-beam ITO electrodes. The peak responsivity of these e-beam ITO MSM photodetectors was 0.11 A/W at a 3 V bias. For a given bandwidth of 500 Hz, the corresponding noise equivalent power (NEP) and normalized detectivity D* were calculated to be 1.51×10-10 W and 2.96×109 cmHz0.5W-1, respectively.