The persistent photoconductivity effect in modulation Si delta-doped pseudomorphic In0.2Ga0.8As/GaAs quantum well structure

Persistent conductivity effect in modulation Si delta-doped In0.2Ga0.8As/GaAs quantum well (QW) structure grown by metal organic vapor phase epitaxy was examined using Hall effect and magnetotransport measurements in magnetic fields up to 12 T at T=1.7 K. No measurable electron density was found in the QW after cooling down the sample in the dark and the electron density in the V-shaped delta-doped potential well (V-QW) of the modulation Si delta-doped layer was two times lower than the electron density of the same Si delta-doped layer in GaAs. The illumination resulted in the increase of electron density in the V-QW at the beginning and consequently in the population of the ground subband in the InGaAs QW. Due to parallel conduction, a nonmonotonic dependence of Hall density as a function of illumination time was observed. The total electron density in the modulation doped InGaAs/GaAs heterostructure after the illumination became approximately equal to the electron density in the Si delta-doped layer in GaAs. (C) 1997 American Institute of Physics.