Infrared absorption and current-voltage characteristic of Si-doped GaAs/AlGaAs multiple quantum wells (MQW) grown on GaAs (111)A substrate by solid source molecular beam epitaxy has been presented in this paper. Strong polarization dependence was found and the normal incidence absorption is dominant in the (111)A-oriented MQW structure with the peak absorption wavelength around 7 mu m. The final excited state is quite higher than the top of the barrier and the polarization property is complicated by the coupling between the valence heavy hole and light hole states in the continuum subband. The symmetric dark current characteristic to the zero voltage under positive and negative bias conditions attributes to the bias symmetric structures for (111)A-oriented MQW and the negligible outdiffusion of Si during the growth. The activation energies extracted from I-V characteristic curve decrease with increasing bias voltage in an exponential relation. The overall agreement between the activation energy and the calculated result has also been obtained. (c) 2005 Published by Elsevier B.V.