STUDY OF AMORPHOUS INCUBATION LAYER INHIBITION IN n AND p DOPED μc-Si:II THIN FILMS BY OPTICAL METHODS AND ELECTRON MICROSCOPY

摘要

In the case of doped layers for p-i-n solar cells based pc-Si:H, the control of the thickness of the amorphous incubation zone deserves special attention. Since these being very thin layers, the first stage of amorphous growth can damage the properties of the solar cell, not only electrically, but also can negatively influence through high absorbing losses. In this paper n and p type doped μc-Si:H thin films were deposited by Hot Wire Chemical Vapor Deposition at low substrate temperature (Ts～100°C). Pre-heating of the substrates and cyclically varying hydrogen dilution (CVH) were used to inhibit or reduce the formation of the amorphous phase during the first growth stage of the thin layer. By the implementation of an optical method based on Effective Medium Approximation (EMA) in transmittance and reflectance measurements, it was possible to determine both the optical properties and microstructure in surface, bulk and the initial stage of growth of the films. The results have been correlated with those of transmission electron microscopy. The results showed reduction of incubation amorphous thin films below 10 nm range.