Wafer scale high-κ oxides films grown by pulsed laser deposition

Abstract

High-κ (Ga, Cu) co-doped ZnO (GCZO) and high-κ vdW Sb2O3 thin films have attracted many research interests. They are novel high-κ dielectrics compared to common high-κ oxides, such as HfO2, Al2O3, ZrO2, and so on. Acceptor donor co-doping method is a novel method to adjust the dielectric properties of oxides. vdW dielectric materials have attracted many research interests because of their atomically flat surfaces that are free of dangling bonds and a low density of disorder and excellent dielectric performance. Here we want to prepare these novel high-quality wafer-scale high-κ oxides dielectric films (GCZO and Sb2O3) through a low-cost pulsed laser deposition (PLD) film preparation method and apply them in various electronic devices as gate dielectric to enhance the performance of electronic devices by improving their capacitance and reducing power consumption or provide an atomically smooth surface. Additionally, efforts are being made to understand the structural and electrical properties deeply for further optimization and integration into next-generation technologies.

Firstly, a series of large-scale high-κ films of GCZO can be readily fabricated via PLD thanks to a series of different concentration targets. Its synthesis method allows for scalable fabrication and facile integration with 2D materials for scalable electric device fabrication. Then, considering κ and crystal quality of these series films, large-scale high-κ co-doping PLD Ga0.005Cu0.02Zn0.975O (κ=56) films could be used in the SnS2 device. In addition, we deposited ALD Al2O3 in Ga0.005Cu0.02Zn0.975O/GZO/sapphire substrate to meet the requirement of the energy band structure of gate dielectrics. And we used the Trap Assisted Tunneling (TAT) model to fit the gate leakage current vs. gate electric field in Ga0.005Cu0.02Zn0.975O gate dielectric layer. The scalable fabrication of gate dielectrics is a requirement for the scale-up of high-performance 2D electric devices. Our Ga0.005Cu0.02Zn0.975O film possesses a high-κ and excellent dielectric properties in comparison with other common high-κ dielectrics.

Next, we designed an oxygen-assisted low temperature PLD method for the phase-selective growth of α- and β-Sb2O3 thin films with super-high κ (>100) and good homogeneity. The phase transition is realized by tuning the oxygen gas pressure in the growth chamber, evidenced by experimental and density functional theory (DFT) analysis. From the in-depth dielectric analysis of α-Sb2O3, the information about conductivity, conduction mechanism, behavior-equivalent circuit, and dielectric relaxation process were obtained. Using dielectric and electrical measurements, we show that α phase exhibit good dielectric performance and apply it in 2D In2Se3 FET as gate dielectric. Our In2Se3 FET shows larger hysteresis window (36.8V) on Sb2O3 compared to SiO2 (9.6V) because of reduced interface scattering, which means better performance for maintaining the ferroelectric polarization of In2Se3.

Our approach to fabricating GCZO and Sb2O3 dielectrics using PLD may open promising opportunities to promote such unprecedented 2D devices to industry applications.