Density-Dependent Microstructures and Electromechanical Properties of Amorphous InGaZnO4 Semiconductors: An Ab Initio Study

Amorphous oxide semiconductors have been applied to thin-film electronics on the backplanes of organic light-emitting diode (OLED) displays. In mobile and high-refresh-rate display applications, demands have been increasing for both low power consumption and high operation speed of the electronics. Here, based on ab initio calculations, we suggest that density engineering of amorphous InGaZnO4 semiconductors can improve electrical properties. The density of an amorphous material is typically variable over a wide range through process control as well as device design and mechanical operation. It is shown here that increasing the density (up to 6.4 g/cm3) of amorphous InGaZnO4 semiconductors with respect to the conventional density (5.8 g/cm3) widens the electronic energy gap by +3.8% and reduces the effective mass of electrons by −4.3%, simultaneously. In a wide range of 3.6–7.8 g/cm3, the electrical properties are found to vary nonmonotonically, of which the physical mechanisms combined with the microstructures are investigated in depth. Density optimization can ultimately lead to both a reduction of off-state current and an enhancement of electron mobility in amorphous InGaZnO4-based thin-film transistors.