Noise of Ta<inf>2</inf>O<inf>5</inf> and Nb<inf>2</inf>O<inf>5</inf> thin insulating films in the temperature range 10 K to 400 K

Abstract

We have performed investigation of noise and transport mechanisms in insulating films of Ta 2 O 5 and Nb 2 O 5 from the point of view of their application as dielectric layers in capacitors, MOS devices, etc. These dielectric films show high relative permittivity, low leakage current density of the order of nA/cm2 in the electric field 1MV/cm, and high breakdown field of the order of 3–4 MV/cm. Analysis of I–V characteristics performed as a function of temperature allows the identification of dominant conduction mechanisms and corresponding noise sources. Ta 2 O 5 films of the thickness about 28 nm and Nb 2 O 5 thin films of the thickness about 150 nm were investigated. Tunneling current mechanism is dominant for the temperatures below 200 K. In this temperature range current noise spectral density is 1/f type. Poole-Frenkel and Schottky current transport mechanism is dominant for temperatures higher than 350 K. 1/f noise is pronounced in the frequency range bellow 20 Hz, while in the range 20 to 100 Hz GR noise is dominant for low current values. For the insulating layer thickness below 50 nm current noise spectral density is given by the superposition of at least two GR noise components with different time constants. This behavior is observed for the temperature higher than 200 K.