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Commonly, the germane fraction (f = flowrateofGeH4/flowrateofSiH4 + GeH4) is changed to vary the optical gap (Eopt) of amorphous silicon germanium alloy (a-SiGe:H) films. We report that for a particular f, the change of deposition conditions, the flow rate of diluent gas (H2) and the radiofrequency (rf) power density can vary the optical gap (1.67-1.40 eV), the germanium content (41.3-22.5 at%) and the microstructural defect density (0.92-0.42), the mobility lifetime product (ηµτ; 6.81×10-6-1.46×10-8 cm2 V-1) in a wide range. Initially, with the increase of the H2 flow rate up to 20 SCCM for the rf power density of 60 mW cm-2 and up to 30 SCCM for the rf power density of 30 mW cm-2, the microstructural defects decreases, although, the Ge content of a-SiGe:H films increases. The microstructural defects of a-SiGe:H films becomes a direct function of the midgap defect density and a indirect function of ηµτ. Moreover, the nature of diluent gas is also important. We present that in a wide range of optical gap (1.74-1.36 eV) the defect density is lower, and ηµτ is higher for the optimized He diluted film compared to those of the optimized H2 diluted films.

The effect of micro-doping, defect creation, and non-steady state occupation through optical transitions on the electron spin resonance signals found in undoped and weakly doped microcrystalline silicon with a high degree of crystallinity is investigated. The experimental results are in agreement with the assignment of the resonance at g=1.9983 to conduction electrons in the crystalline grains and the resonanccs around g=2.0052 to dangling bonds in the remaining amorphous phase and at the grain boundaries. The simultaneous presence of both resonances can result from a large conduction band offset between crystalline grains and grain boundaries or the amorphous phase. The presence of conduction electron spin resonance in compensated and even p-type material points also to potential fluctuations. Free electrons in interconnected crystalline grains are in agreement with the weakly activated transport found in µc-Si:H at low temperatures.