Deep state of hydrogen in crystalline silicon: Evidence for metastability

After proton implantation into n-type silicon at 45 K, a bistable hydrogen center with a band-gap level E_c-E_t=0.16 eV is observed by deep-level transient spectroscopy. The center anneals at ∼100 K under zero bias with a decay constant ν=(3.0×10¹² s^-1)exp[(-0.29 eV)/k_BT] and at ∼210 K under reverse bias with ν=(1.3×10⁸ s^-1)exp[(-0.44 eV)/k_BT]. In both cases the center regenerates by forward-bias injection at low temperatures. The decay without (with) reverse bias reflects capture of one (two) electron(s). The metastability is ascribed to hydrogen jumps between bond-center and tetrahedral sites as a result of changes in charge states.