Search

Defect interactions among oxygen, carbon, and nitrogen during a three‐step high‐low‐high intrinsic gettering process (1100 °C+750 °C+1000 °C) were studied using differential analysis of Fourier transform infrared (FTIR) absorption spectra of Czochralski‐Si crystals intentionally doped with carbon and nitrogen. Two phenomena related to nitrogen were observed: (1) Nitrogen‐enhanced oxide nucleation in the temperature range from 750 to 1100 °C, thus having a negative effect on the denuding step; and (2) defect interaction associated with carbon during oxygen precipitation was significantly affected by the co‐existence of nitrogen. For the latter effect the first‐step annealing at 1100 °C was crucial. The results presented are consistently interpreted assuming that nitrogen participates in creation of nucleation sites for heterogeneous oxygen precipitation, and also assuming that nitrogen aggregates at the strain regions surrounding precipitates and thus retards Si self‐interstitial migration. This explanation was supported by observed differences in oxygen‐precipitate‐related FTIR absorption and by the behavior of stress‐related photoluminescence D lines.

A systematic Fourier‐transformed infrared‐spectroscopy study of oxygen and carbon in isolated form and as complexes in the silicon lattice has revealed a direct correlation between the decrease of substitutional carbon concentration and the decrease of interstitial oxygen concentration during 750 °C annealing. At a concentration exceeding 2 ppma, carbon was also found to enhance oxide precipitate growth. After completing a three‐step annealing (1100 °C+750 °C+1000 °C), an oxide‐precipitate‐related IR‐absorption band was observed. The changes of the IR‐absorption band were correlated with annealing‐induced changes in the state of carbon. A direct incorporation of carbon into oxide precipitates, and/or carbon interaction with silicon self‐interstitials generated during oxygen precipitation, are suggested to have an effect on reducing lattice strain associated with the oxygen‐precipitation process.

The thermodynamic as well as the dynamic constitutional supercooling criteria are derived for liquid phase electroepitaxy (LPEE) taking into account the Peltier effect and electromigration which control the growth interface temperature and mass transport in the solution, respectively. It is shown that solute transport by electromigration enhances significantly the interface stability during growth. Thus the present treatment explains the experimentally attained stable electroepitaxial growth with velocities as high as 25 μm/min. Furthermore, it defines the geometry of the LPEE configuration and the growth parameters (current density and polarity, temperature and substrate characteristics) which lead to the optimization of surface morphology.

A photoluminescence, photocapacitance, and thermal annealing study of Ga‐rich GaAs has revealed the complex behavior of acceptor levels at 68–77 and 200 meV above the valence band. The concentration of all levels is enhanced by Ga‐rich growth conditions, however, only the 77‐ and 200‐meV levels formed preferably in n‐type GaAs are consistent with a double‐acceptor model of the gallium antisite defect. In p‐type GaAs the 68‐meV level associated with a different single‐acceptor defect is dominant. It is argued that the inhibited formation of double‐acceptor GaAs defects in p‐type crystals is caused by the Fermi‐energy control of the defect formation.

The generation kinetics of thermal donors at 450 C in Czochralski-grown silicon was found to be altered by high-temperature preannealing (e.g., 1100 C for 30 min). Thus, when compared with as-grown Si, high-temperature preannealed material exhibits a smaller concentration of generated thermal donors and a faster thermal donor saturation. A unified mechanism of nucleation and oxygen diffusion-controlled growth (based on solid-state plate transformation theory) is proposed to account for generation kinetics of thermal donors at 450 C, in as-grown and high-temperature preannealed Czochralski silicon crystals. This mechanism is consistent with the main features of the models which have been proposed to explain the formation of oxygen thermal donors in silicon.

Nearly perfect indium antimonide single crystals were studied by x‐ray anomalous transmission using silver Kα radiation and {220} reflections. The depth of abrasion‐induced surface damage was determined using the diffracted integrated intensities. The depth of damage was found to be greater on the B than on the A surfaces for the same amount of abrasion. For unidirectional abrasion the direction of the strain corresponded to the direction of abrasion, but some directional strain was also present when the abrasion was not unidirectional. The measured rocking curve half‐widths were not affected by severe surface abrasion. The effective absorption coefficient was measured to be 10.3 ± 1 cm−1.

Cleaved germanium surfaces, oxygenated at room temperature, were heated under high vacuum and the restoration of their oxygen‐adsorbing capacity was determined. No restoration was observed at 425°C. Above 575°C, however, the oxygen‐adsorbing capacity of the surfaces was completely recovered. Discharge of GeO from the surface was associated with this process. The restoration process followed first‐order reaction kinetics with an activation energy of 56 kcal/mole. Concurrently with restoration a pronounced decrease in the surface area was observed. The results are discussed in terms of the kinetic and energy requirements of the system.

We found that a three‐step high‐temperature annealing leads to intrinsic gettering in oxygen‐lean Czochralski silicon grown in a magnetic field as well as in oxygen‐free float zone silicon. Such thermal treatment has been used thus far for achieving intrinsic gettering only in oxygen‐rich Czochralski silicon. We present experimental characteristics of this new intrinsic gettering process, and we propose a phenomenological explanation involving outdiffusion and precipitation of silicon interstitials rather than oxygen which is involved in the standard intrinsic gettering.

Current oscillations thermally activated by the release of electrons from deep levels in undoped semi‐insulating GaAs were observed for the first time. They were attributed to electric field‐enhanced capture of electrons by the dominant deep donor EL2 (antisite AsGa defect). This enhanced capture is due to the configurational energy barrier of EL2, which is readily penetrated by hot electrons.

The key electronic characteristics of semi‐insulating GaAs, i.e., the Fermi energy, concentration, and occupancy of the midgap donor EL2, and the net concentration of ionized acceptors can all be determined from high‐resolution measurements of the EL2 intracenter absorption. The procedure is based on the measurement of zero‐phonon line intensity before and after the complete transfer of EL2 to its metastable state followed by thermal recovery. The procedure is quantitative, involves no fitting parameters, and unlike existing methods, is applicable even when a significant part of the EL2 is ionized.

A dominant hole trap has been identified in p-type bulk GaAs employing deep level transient and photocapacitance spectroscopies. The trap is present at a concentration up to about 4 x 10 to the 16th per cu cm, and it has two charge states with energies 0.54 + or - 0.02 and 0.77 + or - 0.02 eV above the top of the valence band (at 77 K). From the upper level the trap can be photoexcited to a persistent metastable state just as the dominant midgap level, EL2. Impurity analysis and the photoionization characteristics rule out association of the trap with impurities Fe, Cu, or Mn. Taking into consideration theoretical results, it appears most likely that the two charge states of the trap are the single and double donor levels of the arsenic antisite As(Ga) defect.

A new phenomenon is reported whereby illumination (in the visible spectrum) is converted into mechanical strain (elastic deformation or mechanical vibrations) in CdS wafers with an orientation perpendicular to the crystallographic axis [001]. It is believed that the light modulates the electric field at the surface (surface barrier) and causes an elastic strain due to the converse piezoelectric effect.

p‐type conduction in (000l)‐oriented CdS films sputtered in the presence of phosphine was observed. dc Hall measurements are presented and p‐n junction characteristics are shown.

The superconducting resistive critical field Hr of the bcc region of the Ti–Nb–V ternary system has been studied. Measurements at 4.2°K on cold‐rolled alloys at 10 at.% composition intervals determined that Hr varied smoothly with composition. A maximum in Hr occurred at a valence electron to atom ratio n of 4.4 for pseudobinaries of the system. The ratio of critical field to transition temperature was found to be a function of n alone in qualitative accord with the theory for type II superconductors. A criterion for predicting the behavior of similar systems is presented.

Superconducting transition temperature variation in bcc region of Ti-Nb-V ternary alloys measured as function of valence electrons and composition

Phase studies conducted on the In Sb II - beta Sn system led to the conclusion that the system does not exhibit a two-phase region but rather complete solid solubility under equilibrium conditions.