Photoluminescence ina-Si1−xGex:H alloys

The photoluminescence (PL) of alloys in the system a-${\mathrm{Si}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Ge}}_{\mathrm{x}}$:H shows the presence of two bands, one which peaks at higher energies (1.2–1.4 eV in a-Si:H) and one which peaks at lower energies (0.8–0.9 eV). For all values of x studied (0≤x≤0.52), the position of the low-energy peak is independent of Ge concentration. The samples we have studied exhibit a low-energy tail to the PL efficiency which is of constant magnitude independent of x. There is a departure from this behavior only when the low-energy PL peak is present.