Czochralski Growth Technique Research Articles

InP on patterned Si(001): defect reduction by application of the necking mechanism

InP is grown by low-pressure metalorganic chemical vapor deposition on exactly (001)-oriented, patterned Si substrates. The Si structure consists of narrow stripes of different widths down to 0.6 μm oriented along [110], bound by V-grooves with {111} sidewalls. Transmission electron microscopy (TEM) of (110)-oriented cross sections shows that InP nucleation occurs on (001) as well as on {111} planes which results in a faceted growth. Thereby, the epilayer shape is remarkably different from what one would expect from the substrate structure. By choosing proper geometries, antiphase domain free InP can be grown. Moreover, with increasing thickness of the growing layer the density of stacking faults and microtwins is drastically reduced due to their propagation towards the side planes of the InP stripes. This process is comparable with the necking procedure in the Czochralski growth technique used to obtain single-crystalline material free from defects. The defects reductions results in a smoother surface morphology and an increase of quantum efficiency by more than 50% as compared to planar film material.

Flashlamp-pumped Ti:Sapphire laser with different rods grown by Czochralski and Verneuil methods

The design and the development of a flashlamp-pumped Ti:Sapphire laser is described. Design criteria are discussed and performance improvements using different types of fluorescent UV converters or filters, such as organic dyes or doped glass are presented. We have tested different laser rods at various Ti-concentrations obtained by Verneuil or Czochralski growth techniques. The maximum laser output energy of 540 mJ with a differential efficiency up to 1% was achieved by using only a pyrex filter surrounding the laser rod.

TEM characterization of silicon epitaxial layer grown on Si-TaS2, eutectic composites

Directionally solidified Si/TaSi2eutectic composites for the development of electronic devices (e.g. photodiodes and field-emission cathodes) were made using a Czochralski growth technique. High quality epitaxial growth of silicon on the eutectic composite substrates requires a clean silicon substrate surface prior to the growth process. Hence a preepitaxial surface cleaning step is highly desirable. The purpose of this paper is to investigate the effect of surface cleaning methods on the epilayer/substrate interface and the characterization of silicon epilayers grown on Si/TaSi2substrates by TEM.Wafers were cut normal to the <111> growth axis of the silicon matrix from an approximately 1 cm diameter Si/TaSi2composite boule. Four pre-treatments were employed to remove native oxide and other contaminants: 1) No treatment, 2) HF only; 3) HC1 only; and 4) both HF and HCl. The cross-sectional specimens for TEM study were prepared by cutting the bulk sample into sheets perpendicular to the TaSi2fiber axes. The material was then prepared in the usual manner to produce samples having a thickness of 10μm. The final step was ion milling in Ar+until breakthrough occurred. The TEM samples were then analyzed at 120 keV using the Philips EM400T.

Preparation of perovskite oxides for high Tc superconductor substrates

A variety of materials of the general type A2BB′O6 that have an ordered perovskite structure have been prepared and examined as possible substrate candidates for high Tc superconducting films. Materials containing either Ca or Sr as the A cation and either Ga or Al in combination with Nb or Ta as the B and B′ cations have been shown to be congruent melting compounds. These compounds have melting points easily accessible using conventional rf heating techniques and are therefore materials that could possibly be grown in bulk form using the Czochralski growth technique.

Infrared absorption properties of the EL2 and the isolated AsGa defects in neutron-transmutation-doped GaAs: Generation of an EL2-like defect.

The EL2 and the isolated ${\mathrm{As}}_{\mathrm{Ga}}$ antisite defects in neutron-transmutation-doped (NTD) GaAs were studied by using the infrared (ir) absorption technique concurrent with thermal annealing. The results show that irradiation with low thermal-neutron doses partially decomposes the EL2 complex in semi-insulating (si) GaAs grown by the liquid-encapsulated Czochralski (LEC) growth technique. On the other hand, a small amount of EL2 is generated in as-grown Ga-rich undoped p-type LEC GaAs. The EL2 defect in low-dose thermal-neutron-irradiated samples (both si and p-type) was found to be stable up to 850 \ifmmode^\circ\else\textdegree\fi{}C. High neutron-irradiation doses, however, completely annihilate EL2 but generate a different EL2-like defect (DL2). The DL2 defect is observed after annealing the high-dose NTD samples for 6 min at 600 \ifmmode^\circ\else\textdegree\fi{}C. The DL2 concentration is observed to be larger than that of EL2 in as-grown LEC si GaAs by a factor of 2.3 or higher. The photoquenching and thermal recovery properties of DL2 and EL2 defects are identical. However, the DL2 defect does not exhibit the same thermal stability or the zero-phonon line of the EL2 defect. Thermal annealing kinetics shows that DL2 is composed of three point defects. The residual absorption (unquenchable component) after photoquenching the EL2 (DL2) defect is interpreted as the photoionization of the isolated ${\mathrm{As}}_{\mathrm{Ga}}$ antisite. The present results support the identification of EL2 as a complex defect and cast further doubt on the validity of the model which identifies EL2 as the isolated ${\mathrm{AS}}_{\mathrm{Ga}}$ antisite defect.

Growth of pure and Ta-substituted Ba3(VO4)2 single crystals

A novel substrate material for the epitaxial growth of ferrite layers is presented. Single crystals of barium vanadate (Ba3(VO4)2) and tantalum-substituted have been grown by the Czochralski growth technique. The crystals were characterized with respect to lattice constant, thermal expansion, hardness, dielectric constant, and loss tangent.

Effects of impurities and atmosphere on the growth of Cr-doped gadolinium scandium gallium garnet. I

The Czochralski growth technique was used to prepare crystals of Cr-doped gadolinium scandium gallium garnet. The concentrations of divalent and tetravalent dopants and the oxygen partial pressure in the growth atmosphere were varied to examine their effects on interface stability and growth morphology and on optical absorption at 1 μm in the crystal.

The evolution and modelling of the Czochralski growth technique

The historical development of Czochralski growth is briefly outlined and the importance of process modelling to the further extension of the technique is discussed. Milestones in the evolution of process modelling are noted and work in the author's laboratory on transfer function determination is outlined. The effects of an applied magnetic field on segregation are described. Finally, the advantages and future potential of the Czochralski technique are considered.

Growth of congruently melting gadolinium scandium gallium garnet

The Czochralski growth technique was used to prepare crystals of gadolinium scandium gallium garnet. The congruent melting composition, Gd 2.957Sc 1.905Ga 3.138O 12, was determined iteratively using X-ray fluorescence to measure the composition of the top and bottom of Czochralski-grown boules. No variation in crystal composition or lattice parameter was observed in crystals grown from this composition, although greater than 90% of the initial liquid was crystallized. The congruent composition boule shows much less strain than a similarly prepared crystal grown from a stoichiometric melt.

(Invited) Growth of Undoped Semi-Insulating GaAs Single Crystal

Our recent advances in growth technique for undoped semi-insulating GaAs single crystal are presented. We have succeeded in reproducible growth of homogeneouse undoped semiinsulating GaAs crystal up to 3 inches in diameter with low dislocation density (\\lesssim1×104 cm-2). The technique includes Liquid Encapsulated Czochralski (LEG) growth technique incorporated with a computer automated diameter control (CADC) and with a newly developed in-situ melt purification process. For reducing the dislocation density, the use of a thermal reflector and the optimization of other parameters were examined and discussed.

Surface aspects of crystal growth from the melt

A three-phase boundary between crystal, melt and an ambient phase must be present in all configurations used in the growth of crystals from the melt. Techniques for which the ambient phase is gaseous are briefly reviewed and the role of surface tension effects in determining the statistic and dynamic characteristics of the major growth techniques (Czochralski, floating-zone melting and ribbon growth techniques) are considered. The equilibrium conditions which apply at the three-phase boundary are shown to depend on whether or not the crystal is completely wetted by its own melt. Theoretical descriptions of the shape of the meniscus encountered in the above named growth techniques are reviewed. The dynamic stability of the shape of the growing crystal against perturbations in the parameters which determine the shape of the meniscus are examined. It is shown that, whilst the floating ??? process is inherently self-stabilising, the Czochralski technique requires careful control of the thermal geometry for it to be stable. Finally, the occurence and form of surface tension-driven convection (Marangoni flow) in floating-zone melting and in Czochralski growth is briefly reviewed.

Control of diameter in Czochralski and related crystal growth techniques

The various published methods for the automatic control of the diameter of crystals growing by the Czochralski technique are critically reviewed. The form of the meniscus in Czochralski growth is described and it is argued that the most successful servo-control techniques are those which sense changes in meniscus shape rather than changes in diameter only.

Photoluminescence from carbon and oxygen implanted Si

Abstract Silicon produced by float zone, Lopex, or Czochralski growth techniques were ion implanted with various fluences of carbon, oxygen, or both and annealed to examine the substrate and species dependence of the photoluminescence spectra. Other samples implanted with these impurities were annealed and then irradiated with 2.5 MeV electrons to further study the influence of these common substrate trace impurities on radiative defect formation. Results of this study substantiate earlier suggestions that the 0.970 eV luminescence arises from a carbon-dependent center, while the 0.790 eV luminescence arises from an oxygen-dependent center.

Solid-solution LiTaxNb1−xO3 single crystal growth by Czochralski and edge-defined film-fed growth technique

LiTaxNb1-xO3 (LTN) solid-solution single crystals were grown by the Czochralski (CZ) technique and the edge-defined film-fed growth (EFG) technique. For the CZ technique, the crystal quality was easily impaired by marked cellular growth due to constitutional supercooling as x increased in the melt, except in the vicinity of LiTaO3. The problem was minimized by high thermal gradient (> 300°C/cm) and low pulling rate (<1 mm/h), but striation occured. For the EFG technique, pronounced inhomogeneity due to growth cell was not observed but microvoids existed. The crystal composition of the EFG grown crystal was almost constant, irrespective of weight fraction solidified, g, whereas that of CZ grown crystal varied largely with g. Growth conditions for homogeneous LTN crystal are discussed.