Optical Charge Transfer Spectra and EPR Spectra of Cr 2+ (d 4 ) and Cr 1+ (d 5 ) in CdTe

By EPR experiments is shown that two charge states of chromium impurity are present in CdTe:Cr. The Cr 2+ (d 4 ) state has an acceptor character and can accept an additional electron into the d‐shell. The energy required to change the charge state of Cr 2+ (d 4 ) into Cr 1+ (d 5 ) by transferring one electron from the valence band is about 1.2 to 1.3 eV. The photosensitive EPR spectrum due to Cr 1+ (d 5 ) 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 Cr 2+ (d 4 ).