Optical and Electrical Studies of GaP: Ti

Abstract

The results of optical absorption, photoluminescence, electrical conductivity, and Hall-effect measurements on LEC-grown Gap: Ti are reported. The positiom of the Ti$/T& acceptor level at 4, -0.50 eV and the Ti&/T& donor level at E, + 1.0 eV are established and the photoionization transitions from and to these deep levels are identified in the absorption spectra and from recharging processes. The internal transitions 3A, -3T1(F) and + 8T1(P) of T i 3 are found in absorption and the e lT, transitions of Ti$ are seen in the absorption as well as luminescence spectra. The interpretation of these bands and sharp lines requires to take into account different kinds of electron-phonon coupling. Photoinduced recharging experiments at low temperatures on high-resistance GaP:Ti and GaP:Ti: Zn are consistently explained including the three charge states of Ti&, of the P G~P~ antisite defect, and of the residual F~Q~ impurity.Die Ergebnisse von Messungen der optischen Absorption, Photolumineszenz, elektrischen Leitfiihigkeit und des Hall-Effekts an LEC-geziichtetem GaP:Ti werden mitgeteilt. Die Lagen des Ti$/Tig Akzeptorniveaus bei Ec -0.50 eV und des T a / T i % Donatorniveaus bei E , + 1.0 eV werden gesichert und die Photoionisationsiibergange von und zu diesen tiefen Niveaus werden in den Absorptionsspektren und aus Umladungsprozessen identifiziert. Die inneren ubergiinge 3A, + sT1(F) und 4 3T1(P) des Ti ; : werden in Absorption gefunden und die *E cf lT, Ubergiinge

On the properties of GaP supersaturated with Ti

“…The energy position obtained here is similar to the ones reported previously for localized Ti deep donor levels in GaP, i.e. GaP:Ti with Ti concentration below the solid solubility limit, which would be at about 1 eV [28][29], 1.05 eV [30] or 1.15 eV [31].…”

Effects of uniaxial stress on the absorption lines of and the nature of the Jahn-Teller coupling

“…At low temperatures, the OA spectra in GaAs and InP are characterized by two sharp peaks of the 2 E-2 T 2 zero-phonon line (ZPL) located at 4565.5 cm −1 and 4589.4 cm −1 in GaAs [1,7,[14][15][16] and at 4409.4 cm −1 and 4437.0 cm −1 in InP [1,7,15]. In GaP, the same features have been observed; however, the first peak was found to be split into two components located at 4873.0 cm −1 and 4876.3 cm −1 [17]. Also, the second peak, at 4903.0 cm −1 , has a full width at halfmaximum (FWHM) which is an order of magnitude (≈8 cm −1 ) larger than that of the two components of the first peak.…”

“…The titanium-doped GaP samples investigated were taken from the same LEC-grown boule as was used in earlier investigations; they are n-type semi-insulating with the Fermi level pinned by the Ti 2+ Ga /Ti 3+ Ga level at E c − 0.5 eV (E1 samples; cf. [17]). For measuring the OA, three samples were each cut with dimensions 10 × 4 × 2 mm 3 but with the 10 mm axes parallel to either the 001 , 111 or 110 directions respectively.…”

“…The broad underlying absorption seen in figure 1 is due to the 3 A 2 → 3 T 1 transition of the Ti 2+ ion which is also present in the samples (cf. figure 2 in [17]).…”

Dynamic Jahn-Teller effect in crystals doped with 3d ions

“…The interest in these compounds cames from the need of high resistivity materials with a good thermal stability for electronic and optoelectronic devices. The electron paramagnetic resonance (EPR) spectra in GaP [20] and GaAs [17], the optical spectra of GaAs, [16,21] InP [21] and GaP [19,23,24] show evidence of JT effect. Conflicting interpretative models have been proposed in literature, and the more recent one, suggested by Al-Shaikh et al [24], considers a JT coupling to trigonal and tetragonal modes (even if in a not complete quantum mechanical treatment) which by analyses tells the effect of uniaxial stress on the optical spectra.…”