The correlations between structural, chemical, electrical, optical properties of in situ phosphorus‐doped hydrogenated microcrystalline silicon prepared by plasma‐enhanced chemical vapor deposition have been studied by high‐resolution transmission electron microscopy, secondary‐ion mass spectrometry, electrical conductivity, and optical measurements. Microcrystallinity has been observed at a substrate temperature as low as 100 °C with a 1% dilution of (1% PH3/SiH4) in H2. In situ phosphorous‐doped hydrogenated microcrystalline silicon is best grown at 200–300 °C in terms of microstructure, H and P content, and dopant activation. The effects of thermal processing and the use of silicon nitride cap deposited prior to anneal on the structure and properties of phosphorous‐doped hydrogenated microcrystalline silicon are also reported. The use of a silicon nitride capping layer is shown to inhibit recrystallization of hydrogenated microcrystalline silicon during rapid thermal anneal.