Photo-Hall-Effect Spectroscopy with Enhanced Illumination in p-Cd1-xMnxTe Showing Negative Differential Photoconductivity
Abstrakt
The charge-transport properties of semiconductor and semiinsulator materials are strongly controlled by the crystallographic defects manifesting energy states in the bandgap. In this paper, we study deep levels (DLs) in p-type Cd1-xMnxTe by photo-Hall-effect spectroscopy with enhanced illumination.
We show that the mobility of minority (925 +/- 11 cm(2) s(-1) V-1) and majority (59.6 +/- 0.4 cm(2) s(-1) V-1) carriers can be deduced directly from the spectra by using proper wavelength and excitation intensity. Four deep levels with ionization energies E-t1 = E-V + 0.63 eV, E-t2 = E-V + 0.9 eV, E-t3 = E-C-1.0 eV, and E-t4 = E-C-1.3 eV are detected and their positions in the bandgap are verified by comparison of photogenerated electron and hole concentrations.
The deduced DL model is analyzed by numerical simulations with Shockley-Reed-Hall charge generation-recombination theory and compared with alternative DL models differing in the position of selected DLs relative to E-C and E-V. We show that the consistent explanation of collected experimental data principally limits the applicability of alternative DL models.
We also demonstrate the importance of the extended operation photon fluxes (I > 4x10(14) cm(-2) s(-1)) used in the spectra acquisition for correct determination of DL character. Negative differential photoconductivity is observed and studied by charge dynamic theoretical simulations.