Implantation of Mg+ and C+ ions is carried out in bulk InP substrates using single or several energies up to 400 keV. The net carrier concentration profile at 300K is measured by capacitance-voltage (C-V) method. The ground and excited states binding energies of Mg and C acceptors are determined by low-temperature selective excitation of photoluminescence (PL). Additional sharp exciton-Iike emissions are detected after annealing of the samples. Their intensity is found to decrease with increasing Mg+ or C+ dose. Annealing-induced activation and/or formation of complex defect are the likely candidate mechanisms for the involved defect.

An isotropic optically detected magnetic resonance (ODMR) having a Lorentzian lineshape at g - 2.050 ± 0.003 and linewidth (FWHM) of 67.3 mT is observed in GaP doped with 6 - 9 × 1017 S/cm3. The ODMR at g - 2.050 is believed to arise from free electrons (or holes) in the conduction (valence) band. This ODMR is completely quenched due to non-radiative recombination in the vicinity of g - 1.99.

We have studied the influence of oxygen on the optical properties of Be implanted InP. Be implanted p-type InP without oxygen shows a strong deep photoluminescence (PL) band at 0.82 eV following anneal. As the oxygen concentration increases, the 0.82 eV PL-band disappears. We attribute the disappearance of this PL-band to the formation of oxygen complexes with the implantation induced defects. In epitaxial grown, nominally undoped InP a new PL-line is observed at ~1.2 eV. The paramagnetic state of the phosphorus on indium P^ antisite is observed by optically detected magnetic resonance (ODMR) as a modulation of the photoluminescence in all Be implanted samples without oxygen. The antisite resonance is detected as a reduction of the 0.82 eV PL-band and the 1.2 eV PL-band. The observation of the Fe3+ resonance by ODMR spectroscopy is reported for the first time.

We have developed a characterization technique using spectral photoconductivity that is capable of identifying deep energy levels in gallium arsenide. Our technique requires less sample processing than deep level transient spectroscopy (DLTS) and can be used on semi-insulating (si) gallium arsenide. The technique uses a mid-infrared fourier transform spectrometer for rapid photoresponse versus wavelength measurements. Using this technique we have observed evidence of several below mid-gap energy levels in undoped si gallium arsenide by the spectral PC technique. Spectral PC measurements were made on si GaAs before and after illuminating the cooled samples with high intensity white light at 8K. The PC spectrum typically showed a broad photoresponse that was attributed to multiple energy levels being present in the material. The observed energy levels were: 0.54 eV, 0.44 eV, 0.25 eV, 0.17 eV, 0.14 eV and ~0.10 eV. The shallow photoresponse from the carbon acceptor was not observed. The most striking spectral feature was a sharp ionization edge at about 0.44 eV in all of the samples studied. This energy level correlates to the 0.43 eV intrinsic defect level that has been observed by temperature dependent Hall effect measurements. The 0.44 eV level was also observed in our PC spectrum of a n-type Bridgman grown sample that had shown the 0.43 Hall effect level. The presence of additional deep levels in concentrations comparable to those of EL2 and carbon indicates that the simple model for compensation in si GaAs which invokes only EL2 and shallow impurities needs revision.

Combined photoluminescence and DLTS investigations of semi-insulating and n-type GaAs before and after a 15min, 850°C heat treatment under AsH3 reveal that the treatment which anneals the EL6 center leads also to a disappearence of the O.8eV PL band. The suggested correlation between EL6 and the O.8eV PL is confirmed by the determination of the electron capture barrier of EL6 and the Franck-Condon shift deduced from the temperature dependence of the PL band leading to a consistant Configuration Coordinate diagram of this defect.

Cu diffused GaAs samples have been investigated using different kinds of FΠR techniques and photoluminescence. The results suggest that tne “0.15 eV” level originates from the ioruzation of a neutral, nearly substitutional Cu acceptor at a Ga site. Furthermore, the results indicate a distortion in the [100] direction. The ground state binding energy obtained from the effective-mass-like excited states is 157.8 meV at 6K.

Two defects were observed in thermal neutron irradiated semi-insulating liquid-encapsulated Czochralski (LEC) GaAs materials by using the infrared absorption technique. The first defect was observed before thermal annealing and it has a broad peak at ~0.83 eV. The second defect was observed after annealing the sample at 250 °C for 15 min. The latter defect is an EL2 - like defect, but is thermally unstable at 400 °C with a concentration of about an order of magnitude larger than [EL2] observed in as grown LEC materials. Both defects were found to photoquench with white light or 1.1 eV monochromatic light at 9 K and thermally recovered at 150 K. The concentration of the EL2 - like defect is reduced from 8.5×1016cm3 after annealing the sample at 300 °C for 15 min to 2×1016cm-3 after annealing at 400 °C for 15 min. This defect becomes unquenchable after the latter annealing conditions. An explanation for this behavior is offered.

GaP crystals were irradiated with thermal neutrons with a fluence 1.4 * 10 19 neutrons / cm2 . The isochronal annealing at temperatures up to 800°C resulted in n - type conductivity of irradiated samples. After 800°C anneal 10% of transmuted Ge atoms become neutral donors. Simultaneously the absorption spectrum shows a broad band centered at 1 eV. The similar feature is observed in photoconductivity. The origin of the absorption band is discussed. The band is most likely due to germanium - related defect.

The phonon features in the deep level luminescence (PL) bands related to Fe and Mn and native defects in InP have been clearly identified and the lineshape of the bands are analysed using configuration coordinate model. A consistent set of phonon parameters are determined for the first time.

Traps have been studied by thermally stimulated current spectroscopy (TSC) with intrinsic (1.96 eV) and extrinsic (1.15 eV) light for both In doped and undoped LEC materials grown under various non-stoichiometric conditions. Significant differences are seen in the bulk trap spectra associated with Ga-rich and As-rich material and with isoelectronic In doping. Proximity wafer-annealing at 950° C has been shown to improve minority carrier lifetime in n-type GaAs and we show that in semi-insulating GaAs this causes changes in trap structure. From such thermal studies and the effects of non-stoichiometric growth, the probable nature of the traps commonly seen is inferred.

A shallow acceptor-like defect labeled “A” is frequently incorporated in molecular beam epitaxial GaAs. We report here anomalous photoluminescence effects that are induced by this defect. With increasing concentration of the “A” defect: (1) neutral and ionized donor-bound exciton peaks disappear almost completely even for donor concentration as high as 7×1014 cm-3 and compensation ratio ND/NA≈0.3; (2) a new, sharp line emerges at 1.5138 eV, and (3) the relative intensity and line shape of the free exciton transition change dramatically. These observations are discussed in the perspective of previous reports, where similar effects were, in our opinion, misinterpreted.

We have used 300K Electron Beam Electroreflectance (EBER) and 4. 2K photoluminescence (PL) to measure optical transitions in a series of LEC grown GaAs samples. The contaminants primarily consisted of the individual elements Cu, Mn, and C at levels above 1016/cm3. In unmodified control samples we find evidence of strong excitonic effects in the EBER lineshape even at 300K. For the contaminated samples, we find characteristic impurity transitions below the E0 bandgap of the GaAs in both optical spectroscopies. However, in general the estimated impurity binding energies by EBER are not equivalent to established PL or DLTS values. Specifically, from EBER data we find below E0 (1.424eV at 300K) a Cu peak near 49meV (1.375eV) and a C peak about 39meV (1.385eV) below E0 . An EBER spectrum of the Cu-contaminated sample at 124K shows an asymmetric Cu impurity peak 47meV below E0 . The C feature has been ascribed to either Si or Ge from corresponding PL energies by several earlier researchers. Two samples which had been implanted with Mn and annealed show a peak about 43meV below E0 (1.381eV), and what appears to be a sharp, excitonic transition 10 to 16meV above the E0 . Although these features may be due to Mn alone, the latter observation is suggestive of strain-induced valence band splitting.

The correlated appearance of impurity peaks below the split-off E0 +Δ0 band may allow their assignment to either donors or acceptors in modulated reflectance studies [1,2]. None of the present cases showed corresponding transitions below E0 +Δ0 , suggesting that the observed impurity features arise only from acceptor transitions. Alternatively, the reduction of light penetration into the GaAs above the E0 bandgap, reducing the sample interaction volume, may also explain this null observation.

Photoluminescence and Hall measurements are reported on Ge doped InGaAs layers lattice matched to InP. Ge doping of these samples results in highly compensated material, with the highest Ge content sample giving a p type conductivity with carrier concentration of 5 ×1017 cm-3. Low temperature PL spectra of these samples show a broad peak from 0.55 to 0.77 eV due to Ge. The peak of luminescence shifts to lower energy with increasing Ge content. The peak position shifts to higher energy with increasing excitation like in a D-A pair transition. The PL spectra have been explained on the basis of a model which assumes tail states near the band edges due to disorder produced by the presence of Ge in the lattice.

The 0.11 eV Mn acceptor has been investigated using different kinds of FΠR techniques, Zeeman spectroscopy, and photoluminescence. The results clearly fits into the Зd5+ shallow hole model for Mn° and show that the 0.11 eV level originates from the io-nization of a neutral, substitutional Mn acceptor at a Ga-site. The ground state binding energy obtained from the effective-mass like excited states is 112.4 meV.

Using undoped GaAs containing grain boundary, we performed annealing test to identify the processes occurring during heat treatment. We propose EL2 as a complex of double vacancy, AsGa and Asi. From the concentration change at grain boundary region we temporarily conclude that EL3 is a simple intrinsic defect.

In n-type GaP doping with Mn gives rise to a deep centre due to Mn+2. Its luminescence occurs in the near infrared.

The behaviour of this centre is studied as a function of temperature and the thermal quenching of the luminescence interpreted as due to a non-radiative process to the ground state. The behaviour of another band that appears upon doping with Mn is also discussed.

We present recent results on the applications of Fourier transform techniques to photoluminescence spectroscopy as it relates to both basic and characterization-related semiconductor research. The emphasis here is on demonstrating the advantages of these methods in situations requiring very high spectral resolution and/or very high sensitivity. We also provide an example of the utility of interferometry in performing photoluminescence excitation spectroscopy in spectral regions where broadly tunable laser sources are not readily available.

The generation and dissociation processes of Fe-B pairs in Si crystal are investigated by means of the measurements of electron paramagnetic resonance of Si crystals of various B concentrations doped with Fe. Fe-B pairs are generated due to annealing of the crystals at temperatures around 300 K obeying to the first order reaction kinetics. The activation energy for pair generation is determined to be about 0.65 eV which is almost equal to the migration energy of Fe impurity in a Si crystal. Fe-B pairs are found to be dissociated at tempeatures higher than 150°C leading to the precipitation of Fe.

We observe in photoconductivity (PC) measurements EMT-like excited states of the pseudodonor CrB, which are responsible for the capture of free electrons due to their short lifetime. The energetic position of the ground state can be located at Ev + (292 ± 5) meV. A finestructure of the (CrB)° transition consisting of at least 15 components is observed in PC and high-resolution Fourier transform photoluminescence. In acceptor-free silicon a step in photoconductivity at 205 ± 10 meV is ascribed to interstitial Cr, whereas a second step at ~ 425 meV could be due to substitutional Cr.

Using the perturbed γγ angular correlation technique (PAC) the pairing of Cu with the radioactive acceptor atom 111In in Si is detected. Because of the identity of the electric field gradients the so-called X defect, observed after chemomechanical polishing of Si wafers and known of neutralizing acceptor atoms in Si, is identified as a Cu atom. It is also shown that as-delivered Si wafers already contain Cu atoms which neutralize acceptor atoms if the wafers are annealed at 1173 K.