Decay kinetics of persistent photoconductivity in semiconductors

Observation of persistent photoconductivity in bulk gallium arsenide and gallium phosphide samples at cryogenic temperatures using the whispering gallery mode method

“…The very long decay time of the excess conductivity agrees very well with the rectangular spatial Fermi distribution model of Queisser and Theodorou. [2] GaP on the other hand very quickly achieves persistent photoconductivity after the illuminating light source is switched off. This also is well above the conductivity in darkness before photoconductivity is induced.…”

“…From the rectangular spatial Fermi distribution model of Queisser and Theodorou [2] (their Eq. (11)) the decaying photoconductivity can be expressed as…”

“…The parameter X indicates the order of increasing value of the frequency within a mode family and m is the azimuthal mode number. The mode electric energy filling factors were calculated using (2). The values of electric filling factors were calculated once the relative permittivity was known.…”

“…Persistent photoconductivity is extensively described in the literature [1,2,3,4,5,6] as resulting from hole creation in a semiconductor where the energy gap is smaller than the energy of the illuminating light, thus freeing many new conduction electrons. Once the light source is extinguished recombination occurs.…”

“…One has the persistent photoconductivity resulting from the spatial separation of the photogenerated electrons and holes by macroscopic potential barriers due to band bending at planar surfaces, interfaces, junctions or around doping inhomogeneities. [2,3,4] This model has been extended with local inhomogeneities from defect clusters. [6] The second model has atomic scale microscopic barriers at centers with large lattice relaxation.…”