Efficient visible luminescence from hydrogenated amorphous silicon

We report on optical and structural properties of a new class of efficient visible light emitting semiconductors: low-defect-density a-SiHx alloys. Films are prepared by HOMOCVD from silane and RF plasma from disilane. Optical gaps increase monotonically with H incorporation and decreasing substrate temperatures (200-25°C), while spin densities remain low. New broadband luminescence develops in the alloy band tails and shifts to higher energies with the gap. At ∼ 40% H, gaps reach 2.55 eV and yellow-orange PL peaks near 2.05 eV. Efficient PL persists at room temperature. Emission is attributed to band-tail excitons and phonon cooperation. © 1983.