ELECTRICAL AND PHOTOELECTRONIC PROPERTIES OF CR-DOPED SEMI-INSULATING GAAS

The variation of I-V characteristics and photoconductivity spectra with Fermi-level energy is studied for as-grown or heat-treated Cr-doped semi-insulating GaAs. The I-V characteristics are classified into two types, and the relation among I-V characteristics, Fermi-level energy, and the ionization energy of deep levels is briefly explained with the space-charge-limited current model. On the basis of the dependence of the photoconductivity spectrum and the quenching effect on Fermi-level energy, it is deduced that the photocurrent peak at 0.88 eV is explained by two optical processes, i.e., photoabsorption of the Cr acceptor and the quenching effect causing by the photoinduced electron transition from the valence band to deep level, located at about 0.9 eV above the valence band.