Effect of High Oxygen Partial Pressure on Carrier Transport Mechanism in a-InGaZnO TFTs

Abstract

In this paper, the influence of oxygen partial pressure ( ${P}_{\textsf {O2}}$ ) during physical vapor deposition on the field-effect mobility of amorphous InGaZnO (IGZO) thin-film transistor (TFT) is investigated in a wide range of ${P}_{\textsf {O2}}$ . The field-effect mobility reduced from 12 to 0.1 cm $^{\textsf {2}}/\textsf {V}~\cdot $ s when the ${P}_{\textsf {O2}}$ is increased from 0.3 to 1.5 mTorr. Temperature-dependent TFT measurements suggest that carrier transport in the TFTs deposited at the ${P}_{\textsf {O2}}$ of 0.3 mTorr can be described according to the multiple trap and release/percolation model. However, the carrier transport in the TFTs deposited at the ${P}_{\textsf {O2}}$ of 1.5 mTorr conforms to Mott’s variable-range hopping model. The elastic recoil detection analysis indicates that hydrogen concentration in the IGZO film increased with ${P}_{\textsf {O2}}$ . The X-ray photoelectron spectroscopy results indicate that In vacancy ( ${V}_{\textsf {In}}$ ) defects formed in the IGZO film deposited at high ${P}_{\textsf {O2}}$ . Scattering induced by hydrogen and pinning of Fermi level below the conduction band edge by ${V}_{\textsf {In}}$ are plausible reasons for the low field-effect mobility in TFTs deposited at high ${P}_{\textsf {O2}}$ .