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The effect of thermoelectromagnetic convection (TEMC) was investigated in the system germanium–silicon, grown by the vertical Bridgman method under axial static magnetic fields of up to 5 T. TEMC is generated, if thermocurrents, caused by concentration and/or temperature gradients, are running non-parallel to magnetic field lines. Under the influence of strong axial magnetic fields, the macrosegregation along the growth axis changed from a profile typical for normal freezing toward a concentration profile described by diffusive mass transport. At the same time, the segregation pattern on the microscale (i.e. the non-steady distribution of the silicon incorporation perpendicular to the growth axis) changed significantly. Without magnetic field, no evidence of short-range compositional fluctuations has been detected. Growth under static magnetic fields of B ⩾ 0.5 T and B ⩽ 4 T resulted in strong microsegregation. These compositional fluctuations are in the range of a few micrometers up to several hundred micrometers. The strength increased with the field strength and reached a maximum at a magnetic induction of 2 T. These magnetic field induced inhomogeneities are damped with higher magnetic fields and can nearly be eliminated with a magnetic field of 5 T. Due to their coupling to the static magnetic field and their specific shape, they can be attributed to TEMC.

Experimental results of vapor pressure measurement are presented for the whole temperature and pressure range for the existence of Cd0.95Zn0.05Te17d. Vapor pressure scanning approach was used to outline the maximum nonstoichiometry range and pressure–temperature–composition (P–T–X) phase arrangement of the solidus. Pronounced retrograde solubility on the Te side and rather weak temperature dependence of the metal solubility was registered. Position of the Cd0.95Zn0.05Te17d solidus in P–T–X phase space is represented in T–X and P(i)–T projections (i ¼ Cd, Zn and Te2). Isothermal sections of the sublimation region are presented in partial pressures, and from these, temperature dependence of the crystal composition along the vapor pressure minimum curve is derived. Cd(g), Zn(g) and Te2(g) partial pressures as a function of temperature were deduced for constant crystal compositions X S, which, on the one hand, constituted the thermodynamic basis of crystal growth of Cd0.95Zn0.05Te17d with fixed compositions, and on the other hand, led to evaluation of the partial thermodynamic functions for sublimation of Cd0.95Zn0.05Te17d. Thermodynamic aspects of Cd0.95Zn0.05Te17d sublimation are discussed.

A complex investigation of defect structure of high-resistivity Ge-doped CdTe by a number of optical, photoelectrical and electrical methods was performed. It was found that material properties are strongly influenced by the presence of centers of strong recombination (S-centers) and photosensitivity (R-centers). A model of energy levels dominating the recombination processes in the material was elaborated, where the role of Ge, Fe and Cu related as well as native defects (Cd vacancy) is discussed.

This paper presents efficient numerical methods—the “inverse modeling” method and the adaptive finite element method—for optimizing the heat transport as well as for investigating the heat and mass transport under the influence of convection during crystal growth, especially near the liquid/solid interface. These methods have been applied to industrial Bridgman-furnaces for the growth of 65–75 mm diameter (Cd,Zn)Te crystals.

Knudsen cell mass spectrometry has been applied to study the quasi-binary system CdTe–ZnTe at 900 K. Composition of the vapors, vapor pressures, activities, and free energy of mixing were determined. Activities of CdTe were shown to have negative deviation from ideal behavior, whereas those of ZnTe exhibited positive deviation. Free energy of mixing in CdTe–ZnTe is more negative than that of the ideal solution. Pressure–composition P – X section of the Pressure–temperature–composition P – T – X phase diagram was constructed, and relationship between the composition of the crystal, vapor pressure and composition of the vapor was determined in the whole concentration range. At 900 K, CdTe–ZnTe was found to be a continuous solid solution with no phase separation and without congruent sublimation.

The role which microgravity plays for the understanding of the growth of semiconducting materials is reviewed. Main emphasis is placed on the interaction of fluid flow and mass transport phenomena during different growth processes, the character and strength of surface tension driven flows, the limitations of diffusive transport regimes, and possibilities provided by magnetic fields with respect to support or replace microgravity conditions. Some of the most relevant topics to be investigated during the next decade on board the International Space Station are outlined. The first results of experiments carried out on the ISS are presented.

To study the influence of the growth parameters on structural properties and crystal quality epitaxial layers of AlN and Al x Ga 1-x N (x = 0-1) were grown in an RF-plasma enhanced MBE-system on Si-terminated (00.1) SiC, (00.1) sapphire and (111) Si substrates by varying substrate temperature, growth rate and III/V ratio. The alloy composition of the Al x Ga 1-x N layers was studied by RBS-measurements and the results were compared with X-ray diffraction and with the optical properties obtained from cathodoluminescence (CL). The formation of an Al x Ga 1-x N superstructure is observed with ordered Al and Ga distribution. Increasing degree of chemical ordering is observed with inereasing growth temperature. The CL-spectra at 77 K show relatively sharp near-hand-edge transitions for pure AlN and Ga-rich compositions indicating high material quality. The near-band-edge transition follows the composition of the solid solution connected with a broadening of the peaks and evident optical bowing for samples grown at low growth rates (

Aluminum nitride layers were grown on Si-terminated SiC (0 0 0 1) at various substrate temperatures, growth rates, and V/III-ratios in a RF-plasma enhanced MBE system. Surface morphology detected by AFM is strongly influenced by V/III-ratio. Smooth surfaces with a RMS-roughness below 1 nm are obtained for stoichiometric growth conditions giving the smallest FWHM of the XRD-rocking curves of 190 arcsec. For the growth of a more rough AlN-surface layer (RMS 2–24 nm) atomically smooth areas have been detected around micropipes by AFM indicating changed growth conditions. Lateral extension of this area is increased by reducing the growth rate or the V/III-ratio.

CdTe and (Cd,Zn)Te crystals were compared by their material properties. The compensation mechanism of (Cd,Zn)Te and the influence of deep levels are compared to CdTe. The detector grade of (Cd,Zn)Te is obtained with a peak-to-valley ratio of 3.5 for a 57 Co spectrum. The homogeneity of electrical properties is discussed by photoluminescence and TDCM mappings. Recent applications of (Cd,Zn)Te detectors are presented.

CdTe is one of the most encouraging semiconductor materials in the field of room temperature γ- and X-ray spectroscopy. To improve the detector properties, the ternary systems (Cd,Zn)Te and Cd(Te,Se), and CdTe were grown by vertical Bridgman technique. To achieve low noise detectors, the resistivity of all materials was increased by chlorine doping. The crystals were characterized by electrical (Hall measurements, photoinduced current transient spectroscopy) methods. The numbers of deep levels influencing the resistivity were reduced by introducing Se into the CdTe system. A common deep level close to the middle of the bandgap has been identified, responsible for the compensation effect in all three systems. In addition high resistivity and n-type conductivity were achieved in CdTeSe materials for the first time

CdTe and CdTe 0.9 Se 0.1 crystals were grown by the travelling heater method under different material transport regimes. The different transport regimes in the liquid zone were either caused by diffusion (and residual convection), or by 1 g convection, or by forced convection. The forced convection was produced by a B=2 mT rotating magnetic field (400 Hz) under μg conditions. The equations for describing the model of the rotating magnetic field are derived, showing that the magnetic force term in the Navier-Stokes equation can be calculated separately in the case of μg conditions and small magnetic field. The rotating magnetic field generates a stable steady flow in the solution zone, which improves the radial and axial distribution of μτ products