New types of semiconductors are required in order to develop novel electronic devices with superior properties. After the era of Ge and Si, of III-V compounds and Nitrides, the attention of semiconductor scientists is now turning to oxides. ZnO was the first oxide extensively studied, but also group III-sesquioxides (Al2O3, Ga2O3, In2O3 and their alloys) are very promising, particularly for power electronics, short wavelength photonics, and spintronics. The three materials listed above offer a variety of bandgaps between 8.8 and 2.8 eV and many other interesting features. For example, because of its n-type conductivity, high band gap of 4.8 eV, high breakdown voltage and good chemical and thermal stability, Ga2O3 is an excellent candidate for power electronic devices.
With no doubts, this set of transparent semiconducting oxides will be a major issue for solid-state physicists and electronic engineers in the next years. In order to fully exploit their outstanding physical properties, it is however necessary to develop viable growth deposition processes and learn how to make alloys with the desired composition and structure. This is not trivial as the In, Ga and Al-based oxides have completely different crystallographic lattices.