The effect of threading dislocations on optical absorption and electron scattering in strongly mismatched heteroepitaxial III V compound semiconductors on silicon

The effect of threading dislocations on the optical and electrical properties of InP and GaAs heteroepitaxial layers on (001) silicon was investigated. Charged deep states act as scattering centres for electrons, thus affecting the electron mobility at low temperatures. The electric field arising from charged dislocations causes enhanced optical absorption at wavelengths near the fundamental absorption edge. The mean charge of the threading dislocations in GaAs/Si was found to be considerably higher than that for InP/Si. A model is described relating this effect to a regular arrangement of α-type 60 ° dislocations at extended twin defects which were observed in InP/Si but were absent in GaAs/Si.