The quality and stability of thin-film transistors (TFTs) applied to large-scale displays are crucial to their successful manufacture and commercial applicability. This article introduces a TFT manufacturing process in which the source/drain system is defined by hydrogen doping in the dielectric layer of the top-gate amorphous indium gallium zinc oxide (a-IGZO). A size effect related to this system exists where longer channels allow a greater amount of hydrogen to diffuse into the center of the channel. For shorter channels, this results in a lower energy barrier and a shift in the threshold voltage. A physical mechanism model is proposed to verify the abnormal electrical characteristics caused by hydrogen diffusion into the top-gate a-IGZO. The insights provided by these results can be used to further develop TFTs for use in large-scale display applications.

The laser-induced periodic surface structure technique was used to form simultaneously dual-scale rough structures (DSRS) with spiral-shaped nanoscale structure inside semi-spherical microscale holes on p-GaN surface to improve the light-extraction efficiency of light-emitting diodes (LEDs). The light output power of DSRS-LEDs was 30% higher than that of conventional LEDs at an injection current of 20 mA. The enhancement in the light output power could be attributed to the increase in the probability of photons to escape from the increased surface area of textured p-GaN surface.

In order to better understand the reliability issues in top-gate a-InGaZnO (a-IGZO) thin-film transistors, this study investigates the degradation mechanism of a device under self-heating stress (SHS). After applying hot carrier stress, a negative threshold voltage (VTH) shift, a hump effect, and normally-on current degradation were found. COMSOL simulation results of hydrogen diffusion in the source and drain (n+ region) of a-IGZO show that Joule heat was generated in the channel during SHS, which leads to hydrogen diffusion in the central and side channels. The unequal channel thermal effect results in a hump effect in the electrical characteristics, and the self-heating effect becomes more prominent as the channel width increases. To minimize the effects of these abnormal phenomena under high current operation in future display applications, a method of creating structural divisions in the channel width is used to aid overall heat dissipation and reduce the effect of SHS degradation.

The mechanism of hydrogen-diffusion-induced electrical degradation under the self-heating effect for a top-gate amorphous InGaZnO (a-IGZO) thin-film transistor is examined in this article. Joule heating occurs in channels under high operating currents. The hydrogen in the n⁺ a-IGZO source/drain then diffuses into the channel and shifts the threshold voltage (VTH) in the negative direction. As the thermal conductivity of a-IGZO is lower than that of the surrounding insulator, the heat is preferentially dissipated from the sides of the channel. However, the heat in the center of the channel cannot by dissipated quickly. In addition, the unequal channel thermal effect induces a hump effect in the electrical characteristics, which is observed in COMSOL simulations. Hydrogen diffusion under self-heating stress (SHS) operation increases both the effective channel length and parasitic capacitance. The capacitance measurement method is used to clarify the mechanisms of these abnormal phenomena. Finally, the Joule heating effect is eliminated in a low-temperature environment at 200 K with a constant current, confirming that the degradation is indeed caused by the Joule heating effect.