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Studies were carried out by using Hall-effect, van der Pauw, and relaxation-time measurements on the electrical and optical properties of H(super +)- and Au(super +)-irradiated InGaAs layers. The different results obtained can be compared and would help one to obtain information on the nature of the defects created by these two irradiations.

1 MeV electron irradiated p InGaP was studied for recombination enhance defect reactions.

The frequency response of the admittance of the Bridgman- (Bg-) and Czochralski-(Ca)-grown semi-insulating materials have been studied in the 300-500K range. Conductivity was constant up to a frequency omega at which it is proportional to omega(super.1). Existence of the minimum is related to percolation induced by presence of space-charge regions around As precipitates and charged dislocations. These are seen in Cz, but not Bg, materials. Percolation invalidates the homogeneous conduction assumption made relative to electrical properties of semi-insulating Cz materials.

Spin-dependent recombination and deep-level transient spectroscopic studies of electron-irradiated Czochralski silicon solar cells reveal recombination centers near the midgap level. An Si dangling-bond due to a vacancy cluster causes the formation of the centers. The hole and electron cross sections vary with temperature and represent minority-carrier lifetime of silicon.

Electron irradiation affected the current-voltage characteristics of GaAlAs barriers, grown on n-type doped GaAs. Irradiation caused electron induced defects to substitute native defects. Thermal electron ionization and defect site tunneling characterized a defect assisting process at high temperatures. Electron transport through semiconductor barriers was analyzed as a function of irradiation dose.

Electron irradiation in n-type GaP causes characteristic ionization energies, barriers related to electron capture and hole traps. Characteristic ionization is also associated with energy levels and introduction rates of different electron holes and traps. These characteristics are obtained using deep level transient spectroscopy. Electron irradiation after 4 and 300 kelvin produces the same type of traps. Introduction rates are related to primary displacements. Similarities indicate the defects to be of intrinsic type.

Deep-level transient spectrometer facilitates the identification of recombination centers prevalent in very small concentrations in Czochralski-grown p-si. This analysis provides useful information for achieving control of a material's lifetime. The ionization energy and concentrations of the defect, localized in the vicinity of the gap in the P-type Cz material, is measured. The rates of hole and electron trapping and the barrier energy for hole capture are also evaluated. The analysis of the lifetime of the material as a function of these parameters indicates the dependence of lifetime on the defect.

Periodical delta-doped GaAs reveals a signature of quantum confined interband transitions when experimented upon with photocurrent and photoluminescence. A self consistent calculation of the energies of the confined states co-ordinates with both the techniques. The photocurrent spectrum provides the edge transition energy of the first confined level at low temperature, while Fermi energy is produced by photoluminescence excitation spectrum.

Electron transport through GaAlAs barriers in GaAs was investigated to elucidate the effects of the electric field on the apparent barrier height. The results showed that the Fowler-Nordheim regime became dominant at low temperatures and high electric fields. This indicated that the barrier acted as an insulating layer. At higher temperatures, the thermionic regime provided an apparent barrier height which decreased with the electric field and was equal to the expected band offset when extrapolated to zero field.

The energy levels, electron capture barriers and defect introduction rates of electron-irradiated epitaxial GaAlAs alloys were investigated using deep-level transient spectroscopy. The results showed that the defects had energy levels which were associated with the valence band or the L conduction bands. The importance of the different conduction bands with regard to the electron capture of some defect classes was confirmed.

Defects in epitaxial Si-doped GaInP were investigated using capacitance-voltage and deep level transient spectroscopy measurements. The results showed that the defect featured an ionization energy of 0.435 eV and was located at around 20 meV below the bottom of the conduction band. The influence of the electric fiel on the ionization energy proved that the defect is shallow and was a donor.

Capacitance-voltage measurements and deep-level transient spectroscopy were used to characterize defects in Si-doped (Ga1-xAlx)1-yInyAs materials. Results show only DX centers which were attributed to doping impurities of Si, Te and Sn. The contamination was responsible for the shape of the deep level transient spectrum and its variation in the filling pulse duration. The alloying effect cannot account for any of defects.

The nature and behavior of defects in low-temperature electron-irradiated p-type silicon were investigated using deep-level transient spectroscopy. The results showed that defects which were created after irradiation at 90 and 200 K were different from those observed at 4, 77 and 300 K. This indicated that the presence of two annealing stages between 90 and 200 K and 200 and 300 K. The behavior of electron-induced defects in Si was found to be more complicated than previously thought.

The interstitial donor states produced when lithium (Li) is diffused at 300 degrees centigrade in unintentionally doped gallium aluminum arsenide (Ga1-xAlxAs) layers were investigated. GaAlAs epitaxial layers were grown via molecular beam epitaxy with aluminum values of 0.15, 0.18 and 0.29. Different doping conditions were used to study the formation of these donor states and the probability of the introduction of DX centers afterwards. Capacitance-voltage measurements, secondary-ion mass as well as deep level transient spectroscopic techniques were employed in the study.

Thermal conduction across thin films is measured optically by using the surface thermal lensing effect. Pump-probe laser measurements combined with numerical modeling are used to study thermal conduction in a variety of materials as thin as 10 nm. The method is relatively simple, robust, rapid, and offers an alternative to current techniques. Thermal conductivity in gold films is found to drop from 300 to 100 W/Km when the film thickness is reduced from 2000 to 100 nm. Results for silver, tin and aluminum films are also presented and compared with results from other studies. [ABSTRACT FROM AUTHOR]

The variations of the optical and electrical characteristics of a vertical cavity surface emitting laser based on GaAs quantum wells have been monitored versus irradiation with 1 MeV electrons. The results are understood by the introduction of nonradiative recombination centers in the wells whose characteristics, capture cross section for minority carriers times their introduction rate, can be determined. A similar study performed for proton irradiation shows that the results can be explained in the same way when the introduction rate of the defects is replaced by the proton energy loss into atomic collisions. These results allow us to deduce the equivalence between electron and proton irradiations: A flux of 1 proton cm-2 which loses an energy Enℓ (eV) into atomic collisions is equivalent to a fluence of about 9×10-2 Enℓ cm-2, 1 MeV electrons. [ABSTRACT FROM AUTHOR]

We demonstrate how, using electroluminescence, the parameters characterizing the recombination center induced by irradiation in a solar cell can be measured. Because electroluminescence is able to provide information on an individual cell in a multijunction (MJ) cell device, independently of the others, we apply this technique to measure these parameters in InGaP/GaAs/Ge MJ cells. We then calculate the variations of the open-circuit voltage and short-circuit current of such cells versus fluence. The results are compared with experimental data obtained for 1 MeV electron irradiations. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The study presents detailed isothermal and isochronal annealing recovery of photovoltaic parameters in n[sup +]/p InGaP solar cells after 1 MeV electron irradiation. Correlation of the solar cells characteristics with changes in the deep level transient spectroscopy data observed in irradiated and annealed n[sup +]/p InGaP diodes and solar cells shows that the H2 (E[sub v]+0.50 eV) and H3 (E[sub v]+0.76 eV) defects have a dominant role in governing the minority-carrier lifetime as well as carrier removal. However, capacitance–voltage measurements indicate that other defects must also play a role in the carrier removal process. In addition, the concentration of the H2 defect is found to decay significantly as a result of room temperature storage for 40 days, suggesting that InGaP-based solar cells will display superior radiation tolerance in space. Finally, the deep donor-like-defect H2 is tentatively identified as a phosphorus Frenkel pair. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The parameters characterizing the recombination center induced by irradiation in a solar cell can be measured using electroluminescence. The data derived are only orders of magnitude because the accuracy of two parameters fitting the electroluminescence data is not very good, the parameter A is not correctly known and also the formula is derived with approximations.

Presents a study that irradiated Bulk Czochralski (CZ) and vapor phase epitaxy (VPE) layers of n gallium-arsenic with 1-MeV electrons. Dosage range of the electrons; Temperature range of the electrons; Number of defects detected in CZ and VPE.

Presents a study that proposed a method to measure the minority-carrier trapping cross section for a majority-carrier trap. Proportion of the annealing rate induced by the injection to the rate of minority carrier trapping; Achievement of the minority carrier trapping cross section and its variation with temperature; Examination of the E3 defects.

Presents information on a study which examined the evolution of the deep level transient spectroscopy (DLTS) spectrum associated with the EL2 defect in epitaxial as well as bulk gallium arsenide materials when they are contaminated by oxygen. Discussion on the EL2 DLTS spectrum in oxygen-doped materials; Effects described which are directly correlated with the stoichiometry of the surface region; Analysis of the EL2 spectrum for Al Schottky barriers.

Presents information on a study which investigated the properties of electron and hole traps present in n-type GaAs[sub1-x]P[subx] alloys and their evolution versus the alloy composition through deep-level transient spectroscopy. Determination of the ionization energies of electron and hole traps; Discussion; Conclusion.

Presents a study that evaluated the dependence of sulfur impurity incorporation into gallium arsenide on the growth rate and substrate temperature. Background on a model of impurity incorporation; Measurement of sulfur concentration and variation; Methodology.

Describes results of photoluminescence and photocurrent which provide direct information on the quantum-confined transitions in delta-doped silicon-gallium arsenide. Determination of subband energies; Self-consistent method to solve the Schrödinger and Poisson equations; Effect of a weak silicon diffusion around the delta-doped planes.

Focuses on a study which examined the photoluminescence properties of the DX center in periodically δ-doped Si-Al[subx]Ga[sub1-x]As to test the validity of the small lattice relaxation model of the DX center. Experimental procedures; Description of the typical photoluminescence spectra; Discussion of the photoluminescence of the δ-doped superlattice.

Discusses the application of deep level transient spectroscopy to examine neutron-induced defects in high-purity germanium. Information on neutron-induced defects in germanium; Method used to characterize the defects in p-type and n-type materials; Native defects in high-purity germanium; Discussion on room-temperature irradiation; Origin of the annealing stages.

Studies semi-insulating gallium arsenic material from the compensation of residual acceptor impurities and intrinsic defects which posses a level at midgap. Information on EL2 donor defects; Decription of vapor-phase epitaxy technique; Growth parametes of EL2 concentration.

Characterizes uniformly silicon-doped aluminum arsenide layers and short-period gallium arsenide-aluminum arsenide superlattices grown in the same conditions by molecular beam epitaxy. Significance of superlattices based on gallium arsenide alloys; Characterization of aluminum arsenide layers; Discussion of electron-irradiation-induced defects.

Presents information on a study which investigated the formation of the inversion layer in metal-oxide-semiconductor capacitors under reverse direct current bias. Main generation processes of minority carriers; Solution of the Poisson equation giving the total charge in the semiconductor; Determination of the variation of the inversion charge versus the temperature for a constant surface potential.

Discusses a study which analyzed the kinds of deep levels in GaAs/GaAlAs superlattices, namely the electron-irradiation-induced defects and manganese. Confirmation in both cases; Factor that affects the wave function of a carrier bound to an impurity; Use of transition-metal-ion properties; Sensitivity of deep levels.

Presents a study that applied differential thermal analysis (DTA) in measuring defect total energies in a semiconductor material. Background on the application of DTA on gallium arsenide; Assessment of the importance of measuring defect total energy; Investigation of electron irradiation-induced effects.