Wide gap hydrogenated amorphous silicon for visible light emission

A series of samples of hydrogenated amorphous silicon (a-Si:H) was prepared from silane diluted highly with He by the microwave electron-cyclotron-res onance PE CVD. Such a wide gap (E(g)greater than or equal to 2.0 eV) a-Si:H emits room temperature photoluminescence (PL) in the visible region. We at tempt to reveal the microscopic origin of this PL by monitoring variations of PL intensity vs frequency of infrared vibrations in the vicinity of 2100 cm(-1). We find that oligosilanes -(SiH2)(n)- act as one type of possible luminescence centres. We report also on room temperature electroluminescenc e (EL) from p-i-n junctions. Surprisingly, and unlike p-i-n structures from standard a-Si:H, weak EL radiation with external quantum efficiency of the order of 10(-5)% is emitted under reverse bias only. EL and PL emission sp ectra resemble strongly each other, except high energy wing of the EL spect rum. This high energy widening indicates the participation of hot electrons in the EL excitation mechanism.