Muonium Centers in Crystalline Si and Ge under Illumination

The charged state of implanted positive muons, Mu^±, formed at high temperatures undergoes fast spin relaxation in both Si and Ge under illumination due to a cyclic charge-exchange reaction with photoinduced carriers. In Si, the neutral tetrahedral interstitial muonium state (Mu_T⁰) also collides effectively with carriers to induce reaction, while in Ge the neutral state is unreactive. In particular, in Si at low temperatures, the Mu_BC⁰ center is rapidly converted into bond center muonium (Mu_T⁰) with supervening fast spin relaxation under illumination.