Characterization of photorefractive GaAlAs multiple quantum well structures by ac photoelectromotive force and modulated photocarrier grating techniques Available to Purchase

Simultaneous utilization of ac photoelectromotive (photo-EMF) and modulated photocarrier grating (MPG) techniques for characterization of bipolar transport in semi-insulating photorefractive GaAlAs multiple quantum well structure is reported. From the ac photo-EMF experiment the electrons were determined as the dominant photocarriers for interband optical excitation at $λ=633$ nm. From the self-consistent data obtained from photo-EMF and MPG experiments the diffusion length of the photoelectrons was evaluated as $LD≃1.4±0.2$ μm, and that of the photoholes (minority carriers)—as $LDm≃0.6±0.1$ μm. In the MPG configuration, the contrast of the illuminating interference pattern was controlled by electro-optic modulation of the signal beam polarization, which allowed us to measure dielectric relaxation time of the photoconductor as well. As evaluated by both techniques it proved to be about $τdi≃0.05$ μs for the average light intensity $I0≃0.3$ $mW/mm2.$ The proposed combination of the characterization techniques seems to be especially promising for amorphous a–Si and polymer films.