Fabrication of devices using vacuum deposited a–Si

Abstract

The long-term objective of this work is to produce a stable, efficient amorphous Si (a-Si) solar cell by a safe and inexpensive method. A process of reactive evaporation in a silane ambient was developed. This technique permits the fabrication of "intrinsic-like" a-Si:H. p-Type and n-type samples (carrier type was confirmed by Seebeck measurements) were prepared by the coevaporation of boron or reactive evaporation in a phosphorus ambient. The intrinsic-like samples have a room temperature conductivity of about 2 × 10−12 S cm−1, high temperature activation energies of 0.9 eV, and optical bandgaps near 1.8 eV. An all-amorphous Si:H pin diode was fabricated using this reactive evaporation process. The device consists of a tantalum contact, 20 – 40 nm of phosphorus doped a-Si:H, 300 – 400 nm of undoped a-Si:H, 20 – 40 nm of boron doped a-Si:H, and another tantalum contact.