Performance evaluation of atomic layer deposited TiO2/TiN nanolaminates used as infrared photodetectors

Abstract

We study the interaction with photodetectors of near infrared (NIR) laser light with power P in the range of mW and period τ = 3.55 fs (wavelength λ = 1064 nm, frequency ν = 0.28 PHz). We fabricate the photodetectors by depositing different sequences of thin TiO2/TiN nano-laminates onto glass substrates using atomic layer deposition (ALD). To evaluate the photodetector's performance, we assume Pτ to be the energy transferred to them from NIR laser light, allowing us to extract the photodetector's inductance L at zero bias voltage, and to explicitly link P to the photocurrent ΔI, or photovoltage ΔV, generated by the photodetector. Such a link is observed in the literature, but not justified. We further assume Pλ = P λ/lact to be the effective power illuminating the photodetector with size lact. This assumption enables us to determine the photodetector's current responsivity (πI), noise equivalent power (NEP), and detectivity (D). To establish whether Pτ and Pλ correctly account for the energy and the power involved in the photodetector's interaction with light, we compare L, πI, NEP, and D of our photodetectors to the corresponding parameters of state-of-the-art (SOA) devices reported in the literature. The comparison indicates that the L, πI, NEP, and D of our photodetectors are in the range of SOA devices, thus validating our assumptions on Pτ and Pλ. Finally, our findings provide suggestions on how to improve thin ALD TiO2/TiN nano-laminates as suitable active materials in photodetectors.