SPACE-CHARGE-LIMITED CURRENTS AT LOW-TEMPERATURES IN HYDROGENATED AMORPHOUS-SILICON

Transient and steady-state space-charge-limited currents (SCLCs) have been measured in intrinsic hydrogenated amorphous silicon (a-Si: H) n-i-n+ and p+-i-p+ configurations of various thicknesses in the low-tem perature regime T < 100 K. Transient measurements of the field depende nce of the electron mobility and its dispersion are compared with d.c. SCLC results made on the same samples. At fields above 10(5) V cm-1, the increase in conductivity is dominated by the increase in carrier m obility. A simple model is presented to show that a strongly field-dep endent mobility prevents the build-up of inhomogeneous carrier and fie ld distributions in the bulk of a-Si: H in the SCLC regime. The field enhancement explains the similarity of transport properties measured f or intrinsic a-Si: H in the SCLC regime and for doped a-Si: H in the S CLC-free case.