Effects of Mg incorporation by co-sputtering into the ZnO channel layer of thin-film transistors

Low‐Voltage MgZnO Thin Film Transistors with an Amorphous Al2O3 Gate Insulator Grown by Pulsed Laser Deposition

“…Therefore, the devices with an active layer grown at 300 °C obtain the best electrical performance, with saturation mobilities ( µ sat ) of ≈6.70 cm 2 V −1 s −1 , threshold voltages ( V T ) of ≈0.70 V, subthreshold swing ( SS ) of ≈0.138 V dec −1 and an I on / I off ratio of 10 6 . Compared to previous report results, for enhancement‐type MgZnO‐TFTs, whose threshold voltages were 3.92 ≈ 27.60 V and subthreshold swing values were 0.82 ≈ 4.00 V dec −1 , the threshold voltage of our devices is greatly decreased, and the subthreshold swing is lower than the reported values.…”

“…In traditional TFTs, silicon dioxide (SiO 2 ) is usually used as a gate dielectric material. Nevertheless, because the material exhibits a low dielectric constant ( k ) of ≈3.9, Lee et al had to employ a thicker SiO 2 insulating layer, which resulted in a larger operating voltage for the TFT devices …”

Compositional tuning of atomic layer deposited MgZnO for thin film transistors

“…2(d) and a minimum was observed for the 7:1 composition. This observation is contrary to the interface state densities reported for RF co-sputtered MgZnO TFTs deposited onto SiO 2 /n þ -Si substrates at 300 C. 11 In that study, it was found that the addition of magnesium generally increased N it . This can be explained by the ALD doping mechanism in which the doped ZnO interface with the underlying SiO 2 is predominantly ZnO-like.…”

A study of electrical enhancement of polycrystalline MgZnO/ZnO bi-layer thin film transistors dependence on the thickness of ZnO layer

“…It can control the net electron carrier concentration by suppressing carrier generation via oxygen vacancy formation, so shifts of the threshold voltage during on-state bias stressing can be prevented. However, previous our works of MgZnO TFT, the field effect mobility were decreased from 9.12 cm 2 V À1 s À1 to 3.11 cm 2 V À1 s À1 , as Mg incorporation was increased [5]. Recently, a Monte Carlo simulation combing the grain boundary scattering effect and the 2-D finite-element method Poisson and drift-diffusion solver of polycrystalline MgZnO/ZnO bi-layer by Huang et al [6] led to the observation of improved the mobility of MgZnO on ZnO due to the screening effect of the grain boundary potential by the polarization field and modulated doping.…”

“…The ratio of the conduction band offset (DE C ) and the valence band offset (DE V ) between MgZnO and ZnO has been previously estimated to be about 3:2 from another research group [8]. The optical band gaps of MgZnO and ZnO were derived from previous our study [5], and the band diagrams have been drawn by the estimated values of 3:2 (DE C : DE V ). At the junction interface of MgZnO/ZnO (i.e., the conduction band site), localized high electron density is able to form through the attraction of electrons by the potential arising from spontaneous and/or piezoelectric polarization.…”