ACTIVATED TRANSPORT IN IMPROVED HYDROGENATED AMORPHOUS-GERMANIUM (A-GE-H) - THE INFLUENCE OF COOLING RATE, CONTACTS, ELECTRIC-FIELD AND A-SI-H BARRIERS

Structures of Cr/a-Ge:H/Cr were found to show kinks in the Arrhenius p lots of the conductivity near 170 K with activation energies below thi s temperature being field dependent and much smaller than the typical value of 0.5 eV. This can be explained by carrier injection at the low er temperature, which also explains observed deviations from ohmic beh aviour. The influence of thermally induced effects on the conductivity of the samples is examined by cooling the samples at different rates from 470 K. The physical meaning of the so-called equilibrium temperat ure is critically discussed. Barriers of a-Si:H 10 nm thick, inserted in the middle of a 2 mu m a-Ge:H film result in a nearly step-like dif ferential conductivity: For fields below 300 V/cm its value is 10(-8) (Omega cm)(-1,) and it increases to 10(-5) (Omega cm)(-1) for fields a bove 10(3) V/cm.