Low-Frequency Noise in Amorphous Indium–Gallium–Zinc-Oxide Thin-Film Transistors

We have investigated the low-frequency noise (LFN) properties of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) as a function of frequency, bias, and channel length of devices. The measured noise power spectral density of drain current (
S

_iD
) shows that the low-frequency noise in a-IGZO TFTs obeys the classical 1/
f
noise theory, i.e., it fits well to a 1/
f

^gamma
power law with gamma ~ 1 in the frequency range of 10 Hz to 1 kHz. From the dependence of normalized noise power spectral density (
S

_iD
/
ID

²
) on the gate voltage, mobility fluctuation is considered as a dominant LFN mechanism in a-IGZO TFTs. The magnitude of
S

_iD
/
ID

²
is inversely proportional to the channel length of devices, which indicates that contact noise is insignificant in a-IGZO TFTs.