Gallium arsenide as an optical strain gauge Rev.The effects of vanadium doping on the electrical and optical properties of GaAs were systematically studied in melt-grown crystals prepared by the liquid-encapsulated Czochralski and horizontal Bridgman techniques and in epitaxial crystals prepared by liquid-phase electroepitaxy. By employing deep-level transient spectroscopy, Hall-effect measurements and the V2+ (3d 3) and V3+ (3d 2) intracenter optical-absorption spectra, one vanadium-related level was identified in all crystals, i.e., the substitutional-vanadium acceptor level (y 3 + /y2+) at 0.15 + 0.01 e Y below the bottom of the conduction band. From the absorption measur;-ments we conclude that the vanadium (V4+;V3+) donor level must be located within the valence band. Because of its energy position, the above level cannot account for the reported semi-insulating properties of V-doped GaAs. We observed no midgap levels resulting from vanadium-impurity (defect) complexes. The high resistivity reported for certain V-doped GaAs crystals must result from indirect effects of vanadium, such as the gettering of shallowlevel impurities.
A systematic study of the effects of Ti doping on the electrical and optical properties of GaAs and lnP has been carried out employing both melt and solution-grown crystals. Utilizing deep level transient spectroscopy, Hall effect measurements, photoconductivity, and optical absorption measurements, it was found that Ti introduces two deep levels in GaAs at Ee -0.23 eV and Ee -1.00 eV which were identified as the Ti3+ ITi2+ acceptor level and the Ti 4 + lye + donor level, respectively. In lnP the Ti 4 + ITe +-donor level was found near midgap at Ee -0.63 eV, while the Tj3l-/Ti 2 + acceptor level was found to He within the conduction band. As a consequence of the midgap position of this donor level, we developed a formulation for producing semi-insulating InP based on doping with Ti to compensate shallow acceptors.Resistivities in excess of 10 7 n em can easily be obtained using this technique, This is the first semi-insulating IU-V compound having a compensation mechanism based on a deep donor impurity. In view of the fact that Ti is expected to have 11 very low diffusivity in InP, Ti-doped semi-insulating InP should exhibit far greater thermal stability than Fe-doped InP and thus it should prove technologically significant.
2014 Le spectre d'absorption de photoionisation d'échantillons de GaAs fortement dopés au chrome a été mesuré dans la région d'énergie comprise entre 5 500 et 11000 cm-1 jusqu'à une pression de 9 kbar à 300 K et 77 K. Les mesures de RPE sous excitation optique (1,09 03BCm) montrent que cette absorption est due à un transfert de charge de Cr3+ vers Cr2 +. Un modèle théorique tenant compte de la relaxation de réseau est utilisé pour reproduire les courbes de photoionisation. Les valeurs d'ionisation optique EO et thermique ET ainsi que leur dépendance en fonction de la pression sont obtenues. On trouve une énergie de relaxation ER = EO-ET de l'ordre de 0,17 eV et une section efficace de capture pour l'absorption d'environ 5 x 10-17 cm2. Abstract. 2014 The photoionization absorption spectrum of the strongly Cr-doped GaAs samples was measured in the energy region 5 500-11 000 cm-1 under hydrostatic pressure up to 9 kbar at 300 K and 77 K. The EPR measurements with 1.09 03BCm laser excitation shows that this absorption is due to the charge transfer Cr3+ ~ Cr2+ transitions. The theoretical model which takes into account the lattice relaxation effect is used to fit the photoionization absorption curves. The values of optical ionisation energy EO, thermal ionization energy ET and their pressure dependence are obtained. The relaxation energy ER = EO-ET is found as about 0.17 eV and the absorption cross section as about 5 x 10-17 cm2.
Results on the absorption of intracenter transitions of the Cr'+ impurity charge state (3d") in GaAs are reported for different samples with various free carrier and chromium concentrations. The analysis of the data gives limiting values for the Jahn-Teller energies in the ground and excited states of the Cr'+ impurity. The strengths of these couplings are discussed with different models. The effect of the hydrostatic pressure up to 10 kbars at 300 and 77 K is also reported and it is shown that, in specific conditions, the Cr'+(3d') state can be activated by the pressure against the Cr'+ state. These experiments prove that the Cr'+ energy level is above the GaAs conduction band.
Electron paramagnetic resonance experiments performed at 3.5 K on titanium-doped GaAs are reported. An isotropic spectrum characterised by g = 1.9361 f 0.0005 and a linewidth of 16.5 mT is attributed to Ti3+(3d') substitutional to gallium.
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