Improvement of Electronic Transport Characteristics of Amorphous Silicon by Hydrogen Dilution of Silane

We have investigated the electrical and material properties of intrinsic amorphous silicon deposited with hydrogen dilution of silane. The hydrogenated material was used as intrinsic layers of n-i-p diodes, which showed interesting electrical characteristics. From time of flight (TOF) measurement for our best samples produced at hydrogen to silane ratio of 15, we obtained mobility (µ) values about 3-4 times larger than our standard amorphous silicon (a-Si:H). Approximately a factor of 2 improvement was observed for µτ values. The N D* values of the hydrogen diluted a-Si:H were measured for the first time and show lower ionized dangling bond density than the normal a-Si:H material. At a hydrogen to silane gas flow ratio of 20, some microcrystalline formation was observed in the deposited material. We propose a simple macroscopic model to assess the effect of microcrystals and grain boundaries on the electronic properties of mixed amorphous and microcrystalline material.