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The defect properties of as-etched and annealed porous silicon are studied by electron paramagnetic resonance (EPR) and optically detected magnetic resonance (ODMR). The paramagnetic defect observed is closely related to the Pb0 center at the Si/SiO2 interface. In EPR a minimum defect density of 1016 cm−3 is observed for the as-etched silicon, which reaches a maximum of 8×1018 cm−3 for samples annealed at about 400 °C. In the ODMR experiments, the same dangling bond center is observed on the 1.5 eV luminescence band enhancing the luminescence—but with increased sensitivity and as a decrease of the emission intensity in the infrared emission band at 1 eV of porous silicon.

The electron effective masses for Al0.15Ga0.35In0.5P and Ga0.5In0.5P have been investigated using conventional and optically detected cyclotron resonance. For AlGaInP (partly ordered) it is determined to be m*=(0.14±0.01) m0. For disordered GaInP the mass is found to be m*=(0.092±0.003) m0 and for ordered material (band gap reduction ∼50 meV) m*=(0.088±0.003) m0. The experimentally deduced values are compared with those obtained from five-band k⋅p calculation.

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