TEMPERATURE-DEPENDENCE OF THE DC CONDUCTIVITY OF UNDOPED A-SI1-XGEX-H ALLOYS - INFLUENCE OF METASTABILITY

The effects of alloying on the shape of the Arrhenius plots of the dc conductivity of glow-discharge a-Si1-xGex:H with 0 less-than-or-equal-to x less-than-or-equal-to 1 have been investigated in the temperature range 30-250-degrees-C. For 0 less-than-or-equal-to x less-than-or-equal-to 0.3 the Arrhenius plots show a downward kink or negative concavity around a temperature T(k), whereas an upward kink or positive concavity is observed for 0.3 < x < 1. Thermal quenching from 250-degrees-C induces a lowering of a nonequilibrium dark dc conductivity in the first case and an increase in the second. Good correlation is found between T(k) and the equilibrium temperature T(E) (in the range 90-degrees-C-190-degrees-C) and suggests that the shape of the Arrhenius plots is essentially due to metastability. The possible implications to the change in the density-of-states distribution induced by Ge incorporation and by thermal quenching are discussed.