GaN thin films grown by molecular beam epitaxy (MBE) were characterized by Hall effect measurements in the temperature range from 80 K to 500 K and by photoluminescence spectroscopy (PL) at 2 K and at 300 K. These films were grown by MBE utilizing either electron cyclotron resonance (ECR) plasma activated nitrogen gas or thermally cracked hydrogen azide (HN3) as the source of chemically reactive nitrogen. The electrical properties of the GaN films grown by ECR plasma assisted MBE were found to vary with growth parameters, dominated either by shallow donors with activation energies (ΔE)in the range between 10 meV and 30 meV or deep donor levels (ΔE; > 500 meV). GaN grown by (HN3) gas-source MBE exhibited metallic conduction and electron mobilities <1 cm2/Vs. However, these films displayed sharp photoluminescence lines at 3.360 eV and 3.298 eV and no deep level related luminescence, whereas only broad deep level related emission was observed in the PL spectra of the ECR plasma assisted MBE grown GaN films.

Positron annihilation spectroscopy and cathodoluminescence were employed to study changes in the microstructural and luminescent properties of pure and doped polycrystalline ZnS. All samples show evidence of defect clustering, when sintered at temperatures up to 400 °C, indicated by an increase in the average positron lifetime. The average lifetime of the undoped material is constant (at about 290 ps) from 300 to 700 °C, and then decreases beyond this temperature, due to the out diffusion of vacancy clusters. In comparison, the average lifetime for MnS doped material decreases beyond 600 °C. This decrease in the average lifetime is correlated with an increase in the luminescent intensity of the 585 nm Mn band, indicating that Mn compensation of zinc vacancies contributes to the decrease in the average lifetime. At sintering temperatures above 400 °C, the average lifetime of TbF3 doped material decreases by ∼3 ps / 100 °C, from a peak value of 285 ps, and then at 700 °C drops an additional 15 ps to 260 ps. At 650 °C a change from the distinct Tb spectrum to a broad band emission is observed It is believed that these effects can be linked to the incorporation of Tb3+ ions on Zn2+ lattice sites.

Deep levels in high resistivity p-type 6H-SiC has been studied using optical admittance spectroscopy ( OAS ). Besides the conductance peak due to the band to band transitions, there are three conductance peaks in the spectra of most of the samples. The conductance peak due to the vanadium donor (0/+) level at EV+ 1.55 eV is identified. The persistent photoconductance (PPC) at this defect was also studied. The decay kinetics of the PPC follow the stretched exponential form. The potential barrier against recapture of carriers was determined to be 220 meV for the vanadium donor level.

Impurities and defects with masses smaller than the masses of the host semiconductor crystal atoms typically exhibit vibrational frequencies well above the phonon frequency spectrum. These vibrational modes produce sharp spectral absorption features in the infrared. Because of their strong spatial localization these modes are not affected by neighboring impurities and/or defects with concentrations up to 1019 cm−3. This insensitivity is especially advantageous when the free carrier concentration must be reduced through the introduction of electron irradiation defects or when highly doped thin layers must be investigated. LVM spectroscopy with perturbations such as polarization of the probe light, uniaxial and hydrostatic stress, and isotope substitution has been highly successful in identifying the structure and composition of a large number of defect complexes. Hydrogen, in particular, forming a wide variety of complexes in elemental and compound semiconductors has been extensively studied with LVM spectroscopy. For example, it has been shown recently that nitrogen acceptors are hydrogen passivated in MOCVD grown ZnSe. Carbon and oxygen have been investigated in all major semiconductors with LVM spectroscopy. The extreme simplification of the spectrum of bond centered oxygen through isotope enrichment of several Ge crystals has been demonstrated. Additional recent investigations of importance to the currently much studied semiconductors will be reviewed.

Infrared (IR) absorption and Raman scattering are reported from the localized vibrational modes (LVM) of Al and Si δ-layer superlattices in MBE (100) GaAs grown at 400°C as a function of the total areal concentrations, [A1]A and [Si]A respectively. The Al superlattices show the expected behavior on passing from sub-monolayer (ML) to thicker layers (thin AlAs) since the impurities still occupy only Ga-sites. The behavior is very different from that found for Si δ-layers. In addition to SiGa reported previously, we now show that SiAs, SiGa-SiAs pairs and the electron trap Si-X are also present in Si δ-layers and superlattices for 0.05 ≤ [Si]A≤ 0.5 ML. The conductivity of these structures and the concentrations of substitutional Si in GaAs at all sites fall to zero for [Si]A> 0.5 ML but a Raman feature at 470–490 cm−1, attributed to the vibrations of covalent Si-Si bonds is then detected. This feature is not observed in structures containing very closely spaced dilute (0.01 ML) Si δ-planes. It is inferred that long-range Si diffusion does not occur in the bulk crystal, although there could be surface diffusion during Si deposition. The maximum measured carrier concentrations are always less than 2 × 1019 cm−3, the DX limit. The redistribution of Si amongst the various lattice sites is discussed in terms of SiGa DX-like displacements occurring during growth, followed by local thermally activated diffusion jumps. It is speculated that AsGa antisite defects and Ga-vacancies are produced by this process. The reason why the Si δ-layer is non-conducting remains unclear.

A laser scanning system has been developed by the National Renewable Energy Laboratory for the rapid characterization of crystal defects in single- and poly-crystalline semiconductors. The scanning defect mapping system has been commercialized by Labsphere, Inc. as the PVScan 5000. In the unprocessed material, the system produces digital color maps of the spatial distributions of dislocations and grain boundaries simultaneously. After device fabrication, the PVScan 5000 is used to produce photoresponsivity maps of the light beam induced current (LBIC) on a photovoltaic device such as a solar cell or a photodetector. An additional feature is that it also measures the spatial distributions of optical reflectance, both specular and diffuse, which can be applied to the LBIC maps to determine the internal responsivity of the device. The internal responsivity is proportional to the minority carrier diffusion length of silicon devices. It may be possible, therefore, to determine the diffusion length for certain devices.

A novel technique is introduced to study fast diffusing charged defects in semiconductors. It is based on the capacitance change induced by ion drift in a reverse biased Schottky barrier. It is shown that such charge movement yields exponential capacitance transients, which contain information about the defect concentration and mobility. The method is checked on Li-diffused samples, where the extracted diffusion coefficient are in good agreement with literature data. It is next applied to interstitial copper (Cui) in silicon. In the proposed experiment Cui gives rise to a well defined signal which enables us to investigate near room temperature defect reactions involving Cui. The diffusion data extracted from copper diffused and quenched silicon samples establishes the origin of the signal. Near room temperature precipitation kinetics of Cui are studied and energy barriers are extracted.

The photoconductivity amplitude (PCA) technique with UV laser carrier excitation has been proposed to characterize surface property and subsurface damage. Combining this new technique with mechanochemical polishing has determined the depth profile of the slicing-induced residual damage. Combining SC1 cleaning with this technique allows to determine the depth profile of residual damage induced by mirror polishing. This result leads that the mirror polishing-induced damage can be removed by the SC1 cleaning.

Bulk and surface recombination are the main material parameters that determine the performance of crystalline silicon solar cells. We present a new method for the nondestructive, simultaneous mapping of the diffusion length and the surface recombination velocity of a silicon wafer. The method uses the hardware of the electrolytical metal tracer (ELYMAT). The separation between bulk and surface recombination is achieved by illuminating the sample with laser beams of two different colors. By solving the diffusion equation for both laser penetration depths the diffusion length and the surface recombination velocity can be calculated from the measured diffusion currents. First experiments are presented which show the basic feasibility of the method.

Some possible applications of the low-angle mid-IR-light scattering technique and some recently developed on its basis methods for non-destructive inspection and investigation of semiconductor materials and structures are discussed in the paper. The conclusion is made that the techniques in question might be very useful for solving a large number of problems regarding defect investigations and quality monitoring both in research laboratories and the industry of microelectronics.

The activation of phosphorus implanted into n-type silicon (100) substrate by followed hydrogen ion(H +) implantation was studied by means of spreading resistance technique(SR), secondary ion mass spectroscopy(SIMS) and transmission electron microscopy(TEM).

“The activation ratio” defined by carrier concentration divided by phosphorus concentration was used as a measure of activation of phosphorus. The H + energy, dose and dose rate dependence of activation ratio of phosphorus was investigated.

In the case of thermal annealing at 400 °C for 200 minutes the phosphorus atoms were not activated, on the other hand in the case of H + implantation at 400 °C the phosphorus atoms were activated and the activation ratio was increased almost proportionally with the dose. The SIMS data suggested that the depth profile of phosphorus atoms was not changed after activation by H + implantation. The activation ratio was increased with decreasing the dose rate. The TEM data suggested that the density of residual defects was reduced in the case of lower dose rate. The depth profile of activation ratio was similar to that of hydrogen atoms implanted at 20 °C. From these results the activation and recrystalization mechanism is discussed in the view of contribution of elastic collision process between H + ions and substrate atoms.

PL and TEM have been carried out on SIMOX structures before and after thinning the silicon overlayer by a process of sacrificial oxidation. The implantation and high temperature annealing schedules involved in fabricating SIMOX material result in threading dislocations and stacking fault tetrahedra and pyramidals in the silicon overlayer. The optical activity of these extended defects is found to be low. However, after the sacrificial oxidation, strong dislocation related luminescence is observed, which is attributed to the presence of oxidation-induced stacking faults now present in the overlayer.

P-type (100) silicon wafers were implanted with 28Si+ ions at an energy of 50 keV and to doses of 1 × 1015, 5 × 1015 and 1 × 1016 cm−2, respectively, and annealed in a N2 ambient at temperatures ranging from 700°C to 1000°C for times ranging from 15 minutes to 16 hours. The resulting microstructure consisted of varying distributions of Type II end of range dislocation loops. The size distribution of these loops was quantified using plan-view transmission electron microscopy and the strain arising from these loops was investigated using high resolution x-ray diffraction. The measured strain values were found to be constant in the loop coarsening regime wherein the number of atoms bound by the loops remained a constant. Therefore, an empirical constant of 7.7 × 10−12 interstitial/ppm of strain was evaluated to relate the number of interstitials bound by these dislocation loops and the strain. This value was used successfully in estimating the number of interstitials bound by loops at the various doses studied provided the annealing conditions were such that the loop microstructure was in the coarsening or dissolution regime.

The surface properties of silicon are investigated by the noncontact laser (λ=774nm)/microwave method. The effective surface recombination velocity (Seff) at an n+n high-low junction interface is estimated by fitting the experimental decay curve for excess carriers with the theoretical decay curve. The results show that Seg decreases as the dopant concentration increases and that Seff at the n+n high-low junction formed with a dose of 1×l015 ions/cm2 has values lower than 1 cm/s. And it is shown that Scff is inversely proportional to the potential barrier height of the n+n high-low junction. Similar results are obtained using an N2 laser (λ=337.1nm) instead of a laser diode (λ=774nm, 904nm) as a carrier excitation pulse source.

Experimental evidence is provided for ultrasound stimulated dissociation of metal-acceptor pairs in silicon, and also for enhanced diffusion of metal interstitials which may lead to enhanced pairing. The first effect is found dominant in Fe-doped p-type silicon where ultrasound causes low temperature dissociation of Fe-B pairs. This is in contrast to Cr-doped p-type silicon where ultrasound enhances the formation of Cr-B pairs due to enhanced diffusivity of Cr by as much as two orders of magnitude.

In this study, the metal-acceptor reaction was monitored in situ via corresponding changes of the minority carrier diffusion length measured by non-contact surface photovoltage. Ultrasound-stimulated pair reaction can be utilized for metal diagnostics for the silicon IC industry. Thus, with ultrasound, Cr-B pairing can be reduced from months to hours, making possible the identification of Cr via pairing kinetics in a reasonable period of time.

The results of electric parameters studies of silicon samples with unusual p-n junctions are presented. The junctions appeared after the treatment of homogeneous p-Si wafers by 1–5 keV energy argon ion irradiation at the temperature below 100°C and without doping by any n-type impurities. The model of this phenomena is discussed.

The effect of implantation conditions on the localization of oxygen implanted with substoichiometric doses has been studied. Oxygen ions were implanted into Si wafers coated with a thin oxide film, which was etched off after the implantation. We used various implantation modes. After the implantation, the specimens were studied using SIMS and X-ray diffractometry. The concentration profiles suggest that at the lower implantation temperature, part of oxygen migrates toward the Si-SiO2 interface. The effect does not refer to the usual enhancement of SIMS signal at the surface because the concentration peak is at a depth of about 25 nm. Calculated deformation profiles indicate a compression at the same depth, the effect being the strongest for the low current density. The result suggests that the superficial layer is rich in vacancial-type defects. The coincidence of the deformation and oxygen concentration maxima leads to the conclusion that oxygen migrates toward the surface in the form of A-centers. A similar phenomenon has been observed for sequential low-temperature implantation of oxygen and nitrogen.

Cz-grown p-Si(111) specimens were implanted with O+ ions at an energy of 150 keV and doses of 0.25, 0.5, and 1.0 (·1017) cm−2. The implantation temperatures used were 350 and 650 °C. After the implantation, some of the specimens were annealed at 1000 °C for 1 h in a nitrogen atmosphere. IR data indicated the presence of vacancy-oxygen complexes both before and after annealing, irrespective of implantation temperature. Double-crystal X-ray rocking curves also showed that vacancy-type defects are present.