Point defects in stoichiometric and nonstoichiometric metal oxides for modern microelectronics

Defects in metal oxides play a crucial role in the performance of semiconductor devices in modern microelectronics. Due to different growth techniques and growth parameters, the nature and the concentration of electrically active defects in amorphous and crystalline metal oxides can significantly vary in different applications. Control over such defects becomes very crucial in modern microelectronics as they can also interact with other crystal imperfections that appear after various heat treatments in different atmospheres. In this review, we summarize recent progress in the investigation of the electrical, structural, and optical properties of defects in bulk and thin films of substoichiometric and nonstoichiometric metal oxides (Al2O3, Ta2O5, HfO2, and ZrO2) that have a huge potential in the microelectronic industry. We concentrate our attention on native defects such as vacancies and interstitials and on unintentionally introduced defects with an emphasis on hydrogen and hydrogen-related defects and their complexes that could be created during the growth under O-rich or O-lean conditions. In some recent studies, interstitial hydrogen was shown to act as a source of positive or negative charge in metal oxides depending on the position of the Fermi level. This will be also discussed in detail in the present review.