Density of States-Based Design of Metal Oxide Thin-Film Transistors for High Mobility and Superior Photostability

Abstract

A novel method to design metal oxide thin-film transistor (TFT) devices with high performance and high photostability for next-generation flat-panel displays is reported. Here, we developed bilayer metal oxide TFTs, where the front channel consists of indium-zinc-oxide (IZO) and the back channel material on top of it is hafnium-indium-zinc-oxide (HIZO). Density-of-states (DOS)-based modeling and device simulation were performed in order to determine the optimum thickness ratio within the IZO/HIZO stack that results in the best balance between device performance and stability. As a result, respective values of 5 and 40 nm for the IZO and HIZO layers were determined. The TFT devices that were fabricated accordingly exhibited mobility values up to 48 cm(2)/(V s), which is much elevated compared to pure HIZO TFTs (∼13 cm(2)/(V s)) but comparable to pure IZO TFTs (∼59 cm(2)/(V s)). Also, the stability of the bilayer device (-1.18 V) was significantly enhanced compared to the pure IZO device (-9.08 V). Our methodology based on the subgap DOS model and simulation provides an effective way to enhance the device stability while retaining a relatively high mobility, which makes the corresponding devices suitable for ultradefinition, large-area, and high-frame-rate display applications.

A review of recent advances in transparent p-type Cu2O-based thin film transistors

“…The bilayer channel scheme has received increasing attention among n-type oxide TFTs as it was found to be more promising than single-channel TFTs [57][58][59]. As a first attempt to examine such structure on p-type oxide TFTs, we explored the possibility of fabricating p-type transparent bilayer TFTs that consist of a combination of Cu 2 O and SnO as two separate active layers [60,61].…”

Influence of annealing temperatures on solution-processed AlInZnO thin film transistors

“…In addition, the intensity of crystallization peaks was decreased with the addition of Al, which was identical with the results of TG-DSC analysis the minimal amounts of Al added to IZO was sufficient to suppress crystallization and lead to an amorphous microstructure. were attributed to lattice oxygen and oxygen deficiency in the oxide [20], respectively. The peak at 531.7 eV can be assigned to the oxygen in hydroxide since H is more electronegative than the metals, the M-OH oxygen atoms are less negatively charged than those in oxides, resulting in a shift toward to higher binding energy [21].…”

Overview of electroceramic materials for oxide semiconductor thin film transistors

“…There are several types of dielectric layers which have been used in oxide-based TFTs. They include polymers [78,79], high-k metal oxides [80,81], SiO 2 [82,83], Si 3 N 4 [84,85], and hybrid dielectrics composed of multi-layered films [86,87].…”

“…Interestingly, as we learn about the electronic nature of oxide semiconductors, we note that the mobility values are controllable in the range of 1-30 cm 2 /V · s, as long as device-instability is not a concern [152,153]. Also, some promising results have recently been demonstrated with ultra-high mobility (above 50 cm 2 /V · s) in oxide-based TFTs, by adopting bilayer, active structures such as indium tin oxide (ITO)/IGZO or indium zinc oxide (IZO)/IGZO [87,154]. Research on the selection and synthesis of tailored oxide-semiconducting layers, being proposed to obtain higher field effect mobility values, will be continued.…”