Enhanced optical absorption in microcrystalline silicon

An enhanced optical absorption, compared to crystalline silicon, was observed in the above gap region together with very low defect-connected absorption in microcrystalline silicon (mu c-Si:H) prepared by very high frequency glow discharge technique at 70 MHz. As the mu c-Si:H material has a very low fraction of amorphous phase, a 'crystalline silicon like' absorption model is proposed which associates most absorption properties of mu c-Si:H to the crystalline phase in the material. Thereby the influence of internal strain, microcrystallite boundaries, hydrogen content and elastic light scattering on the absorption properties are discussed.