Optical, Electrical and EPR Studies of GaAs:Ni

Electron Paramagnetic Resonance of Titanium in GaP

“…(ii) The decrease of the EPR signal intensity by about 20 to 30% under illumination with 0.7 eV < hvexc < 2.3 eV is the same as that detected on the 4900 cm-1 h e of the 8A, + 3T1(F) absorption band of Ti% [8].…”

“…The optical absorption spectra of GaP:Ti:Zn A1 samples clearly show the sharp-line spectrum (zero-phonon lines at 0.604 and 0.608 eV) due to Ti$ [8]. Therefore, if the weak isotropic signal measured on these samples is Tirelated, it cannot be due to Ti$ but possibly due to Ti%.…”

“…The arguments in favour of this interpretation are the following: (i) This signal is measured also in n-conducting Gap: Ti samples in which all Ti are in the Ti2f charge state. Whereas in semi-insulating GaP:Ti both the optical absorption spectra due to Tit: and Ti$ can be unequivocally measured, in n-conducting GaP:Ti the characteristic sharp-line spectrum due to Ti& is certainly absent but the bands due to T i : : are measured [8].…”

“…The samples used in E P R experiments were cut from the same LEC-grown boules doped with Ti and co-doped with Ti and Zn on which the optical and electrical investigations described in [8] were carried out. The following types of samples were investigated.…”

“…The decrease between 0.5 and 0.8 eV is due to the decay of the photoinduced centres observed also in the dark. An estimation of the highest achievable concentration of the photoinduced centres PkP4 and Fe& (with hv,,, = and in accordance with the decay rate measured for the photoinduced optical absorption [8].…”