DEVICE-QUALITY POLYCRYSTALLINE AND AMORPHOUS-SILICON FILMS BY HOT-WIRE CHEMICAL-VAPOR-DEPOSITION

We describe how high-quality intrinsic hydrogenated amorphous silicon (a-Si:H), as well as purely intrinsic single-phase hydrogenated polycr ystalline silicon (poly-Si:H), can be obtained by hot-wire chemical va pour deposition (HWCVD). The deposition parameter space for these diff erent thin-him materials has been optimized in the same hot-wire depos ition chamber. A review of the earlier work shows how such high-qualit y films at both ends of the amorphous-crystalline scale have evolved. We incorporated both the amorphous and the polycrystalline silicon fil ms in n-i-p solar cells and thin-film transistors (TFTs). The solar ce lls, with efficiencies in excess of 3%, confirm the material quality o f both the a-Si:H and the poly-Si:H i-layer materials, but more work i s needed to improve the interfaces with the doped layers. The TFTs mad e with a-Si:H and poly-Si:H channels show quite similar characteristic s, such as a field-effect mobility of 0.5 cm(2) V-1 s(-1), indicating that the channel region has amorphouslike character with a quality sim ilar to that of state-of-the-art plasma-deposited a-Si:H TFTs. However , in contrast with plasma-deposited a-Si:H TFTs, the present HWCVD TFT s show no deterioration upon prolonged voltage bias stressing.