High-mobility and low subthreshold swing amorphous InGaZnO thin-film transistors byin situH2plasma and neutral oxygen beam irradiation treatment.

In this work, staggered bottom-gate structure amorphous In-Ga-Zn-O (a-IGZO) thin film transistors (TFTs) with high-k ZrO2gate dielectric were fabricated using low-cost atmospheric pressure-plasma enhanced chemical vapor deposition (AP-PECVD) within situhydrogenation to modulate the carrier concentration and improve interface quality. Subsequently, a neutral oxygen beam irradiation (NOBI) technique is applied, demonstrating that a suitable NOBI treatment could successfully enhance electrical characteristics by reducing native defect states and minimize the trap density in the back channel. A reverse retrograde channel (RRGC) with ultra-high/low carrier concentration is also formed to prevent undesired off-state leakage current and achieve a very low subthreshold swing. The resulting a-IGZO TFTs exhibit excellent electrical characteristics, including a low subthreshold swing of 72 mV dec-1and high field-effect mobility of 35 cm2V-1s-1, due to conduction path passivation and stronger carrier confinement in the RRGC. The UV-vis spectroscopy shows optical transmittance above 90% in the visible range of the electromagnetic spectrum. The study confirms the H2plasma with NOBI-treated a-IGZO/ZrO2TFT is a promising candidate for transparent electronic device applications.

Role ofin-situhydrogen plasma treatment on gate bias stability and performance of a-IGZO thin-film transistors.

This work investigates the effect of anin situhydrogen plasma treatment on gate bias stability and performance of amorphous InGaZnO thin-film transistors (TFTs) deposited by using atmospheric-pressure PECVD. The H2plasma-treateda-IGZO channel has shown significant improvement in bias stress induced instability with a minuscule threshold voltage shift (ΔVth) of 0.31 and -0.17 V under positive gate bias stress (PBS) and negative gate bias stress (NBS), respectively. With the aid of the energy band diagram, the proposed work demonstrates the formation of negative species O2-and positive species H2O+in the backchannel under PBS and NBS in addition to ionized oxygen vacancy (Vo) defects ata-IGZO/ZrO2interfaces are the reason for gate bias instability which could be effectively suppressed within situH2plasma treatment. From the experimental result, it is observed that the electrical performance such as field-effect mobility (µFE), on-off current ratio (Ion/Ioff), and subthreshold swing improved significantly byin situH2plasma treatment with passivation of interface trap density and bulk trap defects.

Thermal Management of GaN-on-Si High Electron Mobility Transistor by Copper Filled Micro-Trench Structure.

Self-heating effect is a major limitation in achieving the full performance potential of high power GaN power devices. In this work, we reported a micro-trench structure fabricated on the silicon substrate of an AlGaN/GaN high electron mobility transistor (HEMT) via deep reactive ion etching, which was subsequently filled with high thermal conductive material, copper using the electroplating process. From the current-voltage characteristics, the saturation drain current was improved by approximately 17% with the copper filled micro-trench structure due to efficient heat dissipation. The IDS difference between the pulse and DC bias measurement was about 21% at high bias VDS due to the self-heating effect. In contrast, the difference was reduced to approximately 8% for the devices with the implementation of the proposed structure. Using Micro-Raman thermometry, we showed that temperature near the drain edge of the channel can be lowered by approximately ~22 °C in a HEMT operating at ~10.6 Wmm-1 after the implementation of the trench structure. An effective method for the improvement of thermal management to enhance the performance of GaN-on-Silicon HEMTs was demonstrated.