B.K. Meyer

Optical and magneto-optical determination of the EL2 concentrations in semi-insulating GaAs

A comparison is presented of two different optical methods to determine the concentrations of both charge states of EL2 defects. It is shown that a discrepancy exists for published optical cross sections and that optical absorption measurements are not suitable to determine the concentrations of the ionized EL2 defects with sufficient precision in semi-insulating GaAs wafers.

Energy levels and photo-quenching properties of the arsenic anti-site in GaAs

Optically detected ESR and ENDOR experiments in p-type GaAs under photoexcitation show that an arsenic-anti-site-As-interstitial complex has energy levels Ev+0.52 eV (AsGa+2+/-AsI) and Ev+0.74 eV (AsGa0+/-AsI). From the occupied AsGa0+/-AsI level an absorption band starts peaking at 1.2 eV. From the investigation of the photoquenching behaviour and metastability of the AsGa+-AsI pair is concluded that the diamagnetic AsGa-AsI complex can be associated with EL2.

Microscopic Identification of Anion Antisite Defects in GaAs by Optically Detected Magnetic Resonance

Anion antisite defects in GaAs have been identified so far by their electron spin resonance (ESR) spectrum as one specific point defect, which was found in as-grown, plastically deformed and electron and neutron irradiated GaAs. By optical detection of electron nuclear double resonance (ODENDOR),it could be shown that several species of anion antisite defects exist having practically the same ESR spectrum, which cannot any longer be taken as “fingerprint” identification for this defect. Recent results of ODESR and ODENDOR investigations in as-grown, plastically deformed and electron irradiated GaAs are reviewed. It is also pointed out that the spin lattice relaxation time is an important quantity for the microscopic identification and the properties of anion antisite defects.

Electron paramagnetic resonance identification of an Fe-Ag pair in CdTe

Electron paramagnetic resonance measurements on bulk CdTe crystals revealed the presence of a new defect with monoclinic symmetry in addition to the isolated Fe3+ (3d5, S=5/2). The angular dependence of the resonance lines can only be explained by assuming a spin S=5/2, an isotropic g-value of g=2.12 and additional fine structure terms D and E with a ratio E/D of 0.091. D is assumed to be much larger than the microwave quantum h nu . On the basis of resolved hyperfine interactions we identify the defect as an Fe-Ag pair.

Electron nuclear double resonance of chalcogen donors in GaP revisited

Using electron nuclear double resonance (ENDOR) of GaP crystals containing shallow S donors it was shown that the ENDOR spectra previously detected optically in the two infrared photoluminescence bands assigned to oxygen in oxygen-doped GaP are indeed due to S donors which must have been present simultaneously in those crystals. Furthermore it is shown that the results of the published ENDOR investigations of both S and Te donors in GaP must be revised. Finally the measured ligand hyperfine interaction of S and Te donors are discussed within the frame of effective mass theory.

Optical and Magnetic Resonance Investigations of Mercuric Iodide Crystals

The optical properties of the red modification of mercuric iodide (H g J 2 ) were studied by optical absorption, magnetic circular dichroism, photoluminescence and optically detected magnetic resonance investigations. The experiments demonstrate the involvment of acceptors with energy levels at E v + 0.14 ± 0.01 eV and 0.15 ± 0.01 eV in the absorption and recombination at 2.2 eV. The g - values are 0.85 and 0.74, respectively.

On the Structure of the S=1 Antisite Defect in Gap

Antisite defects are basic intrinsic defects in III-V compounds. They are formed, when a group V atom occupies a group III site.This defect was first observed and identified by Kaufmann, Schneider and Raeuber (Ka76) in GaP. Here one has a P atom on a Ga site. Depending on the Fermi level of the material, the centre may either act as single donor D++/D+ or as double donor D+/D°. These deep donors may play an important role in charge carrier compensation, and they affect in various ways the efficiency of electronic and electrooptical devices. The single donor D++/D+ with S=1/2 is observed in ESR.