The metastable transformation of EL2 was modelled in terms of an additional acceptor level which permitted activation of the metastable transformation of EL2. It permitted metastable transformation after capturing a hole. The thermal emission of this hole at 80 to 85K caused the metastable transformation of EL2 to be quite ineffective at higher temperatures. The double acceptor, 0.078/0.203eV, was suggested to be a possible actuator.

A.Alvarez, J.Jiménez, M.A.González: Applied Physics Letters, 1996, 68[21], 2959-61