An alternative interpretation of optical absorption spectra due to intracenter transition within EL2 defect in GaAs is provided. The arguments are presented that states originating from the L-valley of the conduction band can account for the presence of the wide absorption band, the no-phonon line and the observed uniaxial stress splittings. Using the analogy to the DX center, this model presents an explanation for the existence of the metastable state of EL2.

Combined positron annihilation and differential thermal analysis have shown that, in bulk GaAs materials, dislocations are decorated with vacancy related defects which recombine with As interstitials originating from As clusters. The role of these dislocations, the role of As source of these clusters are described and the consequences on the material homogeneity discussed.

We report a study of dislocations in In-alloyed GaAs substrate material using space and time resolved photoluminescence (PL). PL intensity maps show that an isolated dislocation cluster is in the center of a dark region with a 50μm radius surrounded by a bright region with an outer radius of 150μm. Lifetime measurements were made in the bright and dark regions. Values as long as 3.5 ns and as short as 250 psec were observed in adjacent bright and dark regions. These measurements indicate that the PL intensity contrast is explained by lifetime variations in these features. This supports the view that the dislocation cluster acts as a source and sink for defects which govern the lifetime in the surrounding material. Temperature dependence of the lifetime indicates two different defects may be involved. Both of these produce deep levels, neither one of which is EL2. A surface passivation technique is used to show that surface recombination is not important to the PL intensity contrast.

Based on transition metal reference levels, we present absolute pressure derivatives for band-edges in GaAs and InP and defects in GaAs. The defect deformation potentials are directly related to the electron-lattice coupling which drives lattice relaxation around the defects. We find an exceedingly large inward lattice relaxation of the EL2 defect in GaAs upon electron emission.

Changes in the electronic properties of bulk GaAs crystals, grown from melts of varied As:Ga ratios, and Si-donor concentrations, were investigated by annealing in the temperature range 850°C to 1050°C. We found a gradual reduction of the free carrier concentration, a corresponding decrease in the luminescence spectral intensity, and a suppression of the near band-edge peaks with annealing time at any temperature. Deep level and impurity concentrations remained essentially constant. The magnitude of these changes was found to be determined predominantly by the annealing time and temperature, and the starting composition of the material We argue for a non-radiative native acceptor defect, or defect complex, forming during the annealing cycle. We present here the thermodynamic interpretation for this behavioi in terms of point defect equilibria.

Time resolved photoluminescence (PL) measurements of the internal 4f-4f transitions of Yb3+ have been carried out in InP and GaP. In InP a nonexponential component is observed in the PL decay, and is interpreted in terms of carrier capture by nonequilibrium Yb3+. At low temperatures the exponential component is found to be much faster (≈12.5 μsec) than expected, and is tentatively associated with a weak coupling to resonant valence band states. As the temperature is increased, the PL intensity and the exponential component of the excited state lifetime are quenched with a thermal activation energy of ≈0.1 eV. This is interpreted as being due to the emission of a hole into the valence band by the neutral Yb acceptor.

Optical detection of magnetic resonance (ODMR) is applied to studies of neutral (“isoelectronic”) complex defects in GaP, via monitoring recombination of the excited bound exciton (BE) state associated with these defects. With examples of isoelectronic complex defects in GaP associated with C, Cu, Li and the PGa -antisite, it is shown how the ODMR data reveal the magnetic properties of both electrons and holes bound at such defects. The procedures to conclude on defect symmetry, structure and identity are also elucidated.

The first experimental evidence of an isolated self-interstitial defect in an as-grown semiconductor is reported. An optically detected magnetic resonance spectrum observed in GaP [0] was identified as arising from a Ga selfinterstitial. The large isotropic hyperfine splittings (g = 2.003 (3), A(69Ga) = 741(5)×10−4 cm−1 and A(71Ga) -941[5]×10− 4 cm−1) revealed that a single Ga atom at a Td-symmetric site is the center of the defect. The interstitial nature is established by theoretical considerations. The spin dependent recombination process is attributed to a non-radiative donor-acceptor-pair process involving the Ga++ state which is in competition with a radiative (Odeg; - A° ) pair process and an electron capture process at O-donor.

The paper presents a systematic study of grown-in and process-induced defects on LEC GaAs substrates. Defects have been revealed by photoetching the wafers with diluted Sirti-like solutions after various processing steps. MESFET arrays have been processed on the wafers and a systematic mapping of the I-V characteristics has been performed. A correlation between various defect configurations and the FET threshold voltage shifts has been established.

The diffusivity of Si and P in GaAs encapsulated with heavily-doped polysilicon (poly-Si) is correlated to the flux of Ga and As diffusing from the substrate into the encapsulant. A model based on the diffusion of vacancies into the GaAs is proposed and used to simulate the data.

A range of PGa antisite-related complex defects in LEC GaP:Cu, Li was observed with optically detected magnetic resonance. These isoelectronic defects are formed by a compensation of the PGa double donor by the CUGadouble acceptor on adjacent cation sites. T electronic structure of these defects is discussed, as well as their role in non-radiative recombination.

Detailed analyses of positron lifetimes in GaAs have shown that an omnipresent type of defect acts as a shallow positron trap. This trap modifies the experimentally determined bulk lifetime to higher values and also influences the trapping rate into deep traps such as vacancies. It is suggested that the shallow trap likely is associated with boron. An annealing stage around 450°C is found.

Positron lifetime measurements give direct evidence on positron trapping in monovacancy defects in n-type, but not in p-type nor in semi-insulating LEC-grown GaAs. The defects are identified as As vacancies. Two Fermi level controlled transitions have been found in positron lifetime spectra at 0.03±0.01 eV and at 0.10±0.01 eV below the conduction band. We attribute them to the 2-/- and - / 0 ionisation levels of the As vacancy.

Recent reports have demonstrated the possibility of probing acceptor concentrations in bulk semi-insulating GaAs by electronic Raman scattering using 1.06 μm radiation.1 The inefficiency of detectors in this spectral region severely limits sensitivity, precluding extension to epitaxial layers. We will discuss an approach using both 1.06 μm radiation to photo-neutralize acceptors, and a tunable dye laser to excite Raman scattering. Using a cooled CCD detector, an improvement in detection limit of 104 is realized. Comparison of Raman signals with infrared local mode measurements for samples with carbon concentrations from 1×1014 to 4×1015 cm-3 will be reported. The effect of 1.06 μm power density, dye laser wavelength, dye laser power, and sample fluorescence are included.

We propose the existence of a Fermi level stabilization energy in III-V semiconductors which provides a reference level for the electronic part of defect annihilation energies. It is shown that the position of the stabilization energy with respect to the band edges determines the maximum free carrier concentration which can be obtained through doping. The proposed model accounts for previously unexplained trends in implant activation efficiency in III-V semiconductors.

Capacitance bridge measurements of loss on irradiated n-type InSb specimens at low temperatures are reported. A peak in A.C. conductance at ?55K is seen after irradiation and it is attributed to a radiation induced level.

Undoped, n-type InP has been studied utilizing Au-oxide- InP metal-insulator-semiconductor (MIS) structures. Processing variations have included oxide growth techniques, and annealing of grown oxides. Annealing of the devices in N2 or N2 :H2 after oxide formation has reduced reverse saturation current density by up to a factor of 10 and increased barrier height from 0.45 to 0.65 eV. Annealing of the oxide increases refractive index due possibly to a densification or changed chemical structure. ESCA data reveals thin native oxides to be InP04 whereas thermally grown ones also contain P2 05 and In2 03. DLTS data reveals a dominant defect 597 meV below the conduction band.

Dislocations and some other lattice defects were observed in typical III-V semiconducting materials. The usefulness of electron microscopy is emphasized and some examples of characterizing the nature of lattice imperfections are presented here.

The elastic strain in 2 MeV He ion-bombarded pseudomorphic or lattice-relaxd GaInAs is found to vary by 13% over tlhe beam dose range, 5x1012 - 5×1015 cm-2, with a minimum at 5×1013 cm-2. The data suggest a beam-induced annealing effect at lower doses and the build-up of radiation damage at higher doses, which are also indicated by the phonon line shift data. The phonon shift and the elastic strain in lattice-relaxed GaInAs, bombarded with 15 MeV Cl ions, are approximately the same as in an ion-bombarded bulk GaAs. The lattice mismatch in parallel constant decreases for a sample with a lower misfit and increases for a sample with higher misfit with increasing beam dose. The phonon shift in a pseudomorphic GaInAs bombarded with 15 MeV Cl ions is smaller than in the relaxed samples by a factor of two.

Germanium doping of InGaAsP epitaxial layers grown by liquid phase epitaxy produces n type conduction with a net distribution coefficient KGe∼ 5×10-3. In addition, Ge doping introduces a broad band (∼0.2eV) of efficient luminescence which is red shifted with respect to the band edge. The intensity of this band grows with increasing Ge concentration. In all the samples, the integrated intensity of the broad band varies relatively less in the temperature range 15K to about 90K. At higher temperatures, the intensity falls exponentially with an activation energy of 0.05 - 0.07 eV. The emission spectra are compared with the configuration-coordinate model of the emission from a Ge related complex.