Ion irradiation-induced disordering of semiconductors: defect structures and applications

This brief review focuses on defect and microstructural issues of importance for applications of ion irradiation of semiconductors. Ion irradiation of semiconductors can lead to a variety of disordering behaviour that depends not only on the semiconductor material but also on implantation parameters such as ion fluence, flux, energy and mass as well as the implantation temperature. In some cases, such as silicon implanted at or below room temperature, ion disorder leads readily to amorphization, whereas some other semiconductors, such as aluminium arsenide and gallium nitride, undergo very efficient dynamics annealing even at liquid nitrogen implantation temperatures and are difficult or even impossible to amorphize. In cases of efficient dynamic annealing a rich array of defects can result during implantation. This presentation gives examples of the defect structures that can arise during implantation and subsequent annealing of semiconductors and illustrates how disorder can be exploited to advantage in both electronic and optoelectronic device applications. In particular, open volume defects such as voids and cavities can be generated in silicon and these can be used to selectively remove metal impurities. In compound semiconductors such as zinc oxide, ion irradiation can be used to introduce defects that raise the resistivity of the material by more than seven orders of magnitude. Finally, disorder can be used to promote intermixing of the elemental constituents in adjacent multi-layer compound semiconductors and this process has been used to tune the wavelength of lasers.