The electrical and photosensitive characteristics of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) related to the oxygen vacancies V̈_O are discussed. With the filling of V̈_O of ratio from 14 to 8, the electron density of the a-IGZO channel decreases from 7.5 to 3.8 ( ×10¹⁶ cm^-3); the saturation mobility of the TFT decreases from 3.1 to 1.4 cm^-2/(V · s); the threshold voltage increases from 7 to 11 V for the TFT with a lower on-current; and the subthreshold slope increases from 2.4 to 4.4 V/dec for the TFT with a higher interface defect density of 4.9 × 10¹¹ cm^-2, the worst electrical stability of V_th ~ 10 V, and a hysteresis-voltage decrease from 3.5 to 2 V. The photoreaction properties of a-IGZO TFTs are also sensitive to the oxygen-content-related absorption of the a-IGZO channel. With the lowest content of oxygen in the channel, the TFT has the largest photocurrent gain of 50 μA (V_g = 30 V; V_d = 10 V) and decrease in V_th ( V_th V) at a high light intensity. The light-induced change of TFT characteristics is totally reversible with the time constant for recovery of about 2.5 h.

We investigated the effects of bias stress on a passivation-free InZnO thin-film transistors (a-IZO TFTs) exposed to either the atmosphere or a vacuum. The magnitude of threshold voltage shift increased with the application duration of bias stress, to an extent that was much larger in the atmosphere than in the vacuum. The threshold voltage recovered slowly to its nearly initial value when the gate bias stress was removed. The electrical metastability was attributed to the interaction between the exposed a-IZO backchannel and oxygen/moisture from the atmosphere, and a dynamic equilibrium was finally achieved, regardless of the polarity of stress voltage.

The paper presents a computational approach to reconstruct the shape of a perfectly conducting cylinder. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equations is derived and the imaging problem is reformulated into an optimum one. By using the genetic algorithm, the shape of the object can be reconstructed. The genetic algorithm will always converge to a global extreme solution no matter what the initial estimate. Numerical results are given to demonstrate that, even when the initial guess is far away from the exact one, good reconstruction has been obtained. In such a case, the calculus-based method often becomes trapped in a local extreme.

By using microwave annealing technology instead of thermal furnace annealing, this work elucidates the electrical characteristics of amorphous InGaZnO thin film transistor (a-IGZO TFT) with a carrier mobility of 13.5 cm²/Vs, threshold voltage of 3.28 V, and subthreshold swing of 0.43 V/decade. This TFT performance with microwave annealing of 100 s is well competitive with its counterpart with furnace annealing at 450 °C for 1 h. A physical mechanism for the electrical improvement is also deduced. Owing to its low thermal budget and selective heating to materials of interest, microwave annealing is highly promising for amorphous oxide in semiconductor TFT manufacturing.

This letter studies the correlation of postannealing treatment on the electrical performance of amorphous In-Zn-Sn-O thin-film transistor (a-IZTO TFT). The 400 °C annealed a-IZTO TFT exhibits a superior performance with field-effect mobility of 39.6 cm ² /Vs, threshold voltage (Vth) of -2.8 V, and subthreshold swing of 0.25 V/decade. Owing to the structural relaxation by 400 °C annealing, both trap states of a-IZTO film and the interface trap states at the a-IZTO/SiO ₂ interface decrease to 2.16×10 ¹⁷ cm ^-3 eV ^-1 and 4.38×10 ¹² cm ^-2 eV ^-1 , respectively. The positive bias stability of 400 °C annealed a-IZTO TFTs is also effectively improved with a V _th shift of 0.92 V.