Optical Charge Transfer Spectra and EPR Spectra of Cr2+(d4) and Cr1+ (d5) in CdTe

By EPR experiments is shown that two charge states of chromium impurity are present in CdTe:Cr. The Cr2+(d4) state has an acceptor character and can accept an additional electron into the d‐shell. The energy required to change the charge state of Cr2+(d4) into Cr1+(d5) by transferring one electron from the valence band is about 1.2 to 1.3 eV. The photosensitive EPR spectrum due to Cr1+(d5) shows that the observed intense exponential absorption tail is due to this charge transfer process. The shape of the exponential tail is also investigated. It is suggested that the exponential character of the absorption tail is due to the presence of a Jahn‐Teller effect in the ground state of Cr2+(d4).