Unexpected Infrared Absorption Spectrum of Magnesium Donor Impurities in Silicon

The group-II magnesium, when diffused into silicon, is well-known to behave as an interstitial helium-like double donor. Previous study clearly indicates that the excitation spectrum of neutral magnesium donor has many features remarkably similar to those of group-V donors in silicon. Recently, however, from further study of the infrared absorption spectrum of magnesium donors, unexpected results quite different from a typical donor spectrum in silicon have been observed.