Light exposure of multilayers consisting of alternating 2.5 nm thick a-Si:H and about 40 nm thick a-SiNx:H produces a large metastable excess dark conductance. This appears to be due to metastable defects in a-SiNx:H produced by hopping injection of photocarriers from the a-Si:H. They anneal at an equilibration temperature TE∼460°K. These metastable defects are created with the same efficiency between 4K and 300K. The efficiency rapidly falls above 350K. The metastable defects have the same anneal temperature regardless of creation temperature. The mechanism of defect creation will be compared with that in a-Si:H.