ABSTRACT
Dielectric layers are widely used in ferroelectric applications such as memory and negative capacitance devices. The wake-up and the split-up phenomena in the ferroelectric hafnia are well-known challenges in early-stage device reliability. We found that the phenomena even occur in the bilayer, which is composed of the hafnia and the dielectrics. The phenomena are known to be affected mainly by oxygen vacancies of hafnia. Dielectric layers, which are often metal oxides, are also prone to be affected by oxygen vacancies. To study the effect of the dielectric layer on the wake-up and the split-up phenomena, we fabricated ferroelectric thin-film capacitors with dielectric layers of various thicknesses and measured their field-cycling behaviors. We found that the movement of oxygen vacancies in the dielectric layer was predominantly affected by the polarization state of the ferroelectric layer. In addition, the mechanism of the field-cycling behavior in the bilayer is similar to that in ferroelectric thin films. Our results can be applied in ferroelectric applications that use dielectric layers.
ABSTRACT
We demonstrate the programmable light intensity of a micro-LED by compensating threshold voltage variability of thin-film transistors (TFTs) by introducing a non-volatile programmable ferroelectric material, HfZrO2 (HZO) into the gate stack of the TFT. We fabricated an amorphous ITZO TFT, ferroelectric TFTs (FeTFTs), and micro-LEDs and verified the feasibility of our proposed current-driving active matrix circuit. Importantly, we successfully present the programmed multi-level lighting of the micro-LED, utilizing partial polarization switching in the a-ITZO FeTFT. We expect that this approach will be highly promising for the next-generation display technology, replacing complicated threshold voltage compensation circuits with a simple a-ITZO FeTFT.
