Characterization and optimization of AlGaN/GaN metal-insulator semiconductor heterostructure field effect transistors using supercritical CO2/H2O technology

The impact of supercritical CO2/H2O technology on the threshold-voltage instability of AlGaN/GaN metal-insulator semiconductor high-electron-mobility transistors(MIS-HEMTs) is investigated. The MIS-HEMTs were placed in a supercritical fluid system chamber at 150℃ for 3 h. The chamber was injected with CO2 and H2O at pressure of 3000 psi(1 psi ≈ 6.895 kPa). Supercritical H2O fluid has the characteristics of liquid H2O and gaseous H2O at the same time, that is, high penetration and high solubility. In addition, OH-produced by ionization of H2O can fill the nitrogen vacancy near the Si3N4/GaN/AlGaN interface caused by high temperature process. After supercritical CO2/H2O treatment, the threshold voltage shift is reduced from 1 V to 0.3 V. The result shows that the threshold voltage shift of MIS-HEMTs could be suppressed by supercritical CO2/H2O treatment.

Hysteresis-Free, High-Performance Polymer-Dielectric Organic Field-Effect Transistors Enabled by Supercritical Fluid

Organic field-effect transistors(OFETs)are of the core units in organic electronic circuits,and the performance of OFETs replies critically on the properties of their dielectric layers.Owing to the intrinsic flexibility and natural compatibility with other organic components,organic polymers,such as poly(vinyl alcohol)(PVA),have emerged as highly interesting dielectric materials for OFETs.However,unsatisfactory issues,such as hysteresis,high subthreshold swing,and low effective carrier mobility,still considerably limit the practical applications of the polymer-dielectric OFETs for high-speed,low-voltage flexible organic circuits.This work develops a new approach of using supercritical CO_(2) fluid(SCCO_(2))treatment on PVA dielectrics to achieve remarkably high-performance polymer-dielectric OFETs.The SCCO_(2) treatment is able to completely eliminate the hysteresis in the transfer characteristics of OFETs,and it can also significantly reduce the device subthreshold slope to 0._(2)5 V/dec and enhance the saturation regime carrier mobility to 30.2 cm^(2) V^(-1) s^(-1),of which both the numbers are remarkable for flexible polymer-dielectric OFETs.It is further demonstrated that,coupling with an organic light-emitting diode(OLED),the SCCO_(2)-treated OFET is able to function very well under fast switching speed,which indicates that an excellent switching behavior of polymer-dielectric OFETs can be enabled by this SCCO_(2) approach.Considering the broad and essential applications of OFETs,we envision that this SCCO_(2) technology will have a very broad spectrum of applications for organic electronics,especially for high refresh rate and low-voltage flexible display devices.