High-performance diamond/amorphous silicon p-n+ heterojunctions

We have fabricated high-performance p-n(+) heterojunctions of homoepitaxial diamond (B-doped film: p type) and hydrogenated amorphous silicon (P-doped a-Si:H film: n type). Current-voltage (I-V) characteristics of the p-n(+) heterojunctions at room temperature show excellent rectification properties with an ideality factor n of 1.23 and undetectable leakage current at reverse bias condition. Capacitance-voltage (C-V) characteristics show a large difference of space-charge densities (net acceptor densities) in the bulk and near-surface (interface) regions of the diamond films and a strong frequency dependence in the forward-bias region. The former result indicates that the hydrogen passivation of boron in diamond during the a-Si:H deposition occurs in the near-surface region which gives rise to a reduction of the acceptor density in the depletion region. The latter result indicates an increment of hydrogen-related defect states in the near-surface region of the diamond film. An idealized energy-band diagram for the p-n(+) heterojunctions has been constructed on the basis of the negative-electron-affinity model. (C) 2004 American Institute of Physics.