Hole Dangling Bond Capture Cross-Sections in a-Si:H

Abstract

It is demonstrated that the occupation statistics for a Gaussian distribution of dangling bond states may account for the measured variation of hole mob ility-lifetime values in hydrogenated amorphous silicon as the Fermi energy is systematically varied by doping fro m about 0.55 eV to 1.05 eV belo w the conduction band edge. An assessment of how the deduced dangling bond parameters may be influenced by underlying doping effects suggests that the min imu m cross-section ratio for hole capture into charged (σh - ) and neutral (σh 0 ) dangling bond states requires that σh - /σh 0 ≥ 5. The capture of holes is consequently dominated by charged dangling bonds provided the Fermi energy lies within the upper half of the band-gap. Both σh - and σh 0 are observed to depend upon temperature (T) as σh ∝ T -β wh ich may indicate the presence of tunnelling