Zur Charakterisierung von hochdotierten GaAs-Einkristallen

Investigations of structure defects in high Sn doped GaAs monocrystals grown by the liquid encapsulation technique were carried out using etch techniques, infrared microscopy and X-ray topography. Specific defects in connection with inhomogeneous insertion of the dopand caused by constitutional supercooling and cellular growth could be observed. – Described are the geometry, the distribution and the cause of the occurrence of these defects. The effect of these latter on the luminescense is investigated.     

Defektstrukturuntersuchungen an GaAs-Einkristallen mit Hilfe der IR-Mikroskopie

IR-treatments on Czochralski-GaAs-single crystals are reported being doped with various elements. In using Si and Cr as dopimg materials auto-decoration of the dislocations were observed. In some examples the geometric arrangement and the distribution of the dislocations are discussed.     

Versetzungsnachweis auf {100}-Flächen von GaAs-Einkristallen

For the measurement of etch pit densities of gallium arsenide crystals of the orientation 〈100〉 the etching in KOH-melts is used proposed by GRABMAIER and WATSON . Metallographical and X-ray topographical investigations of the temperature dependence of this etching and of the correlation between etch pit and dislocation are described. The results verify the exact proof of dislocations in GaAs-〈100〉-crystals.     

Einige Erfahrungen mit dem Wachstum von LiTaO3-Einkristallen

LiTaO₃ single crystals are grown by the Czochralski technique using Pt crucibles. They are applied for light guides by Nb diffusion.     

Untersuchung von Heterostrukturen der Mischkristallreihe GaAs/AlAs mit dem Rasterelektronenmikroskop

The investigation of heterojunctions of the mixed crystals series GaAs/AlAs by means of different scanning electron microscopic techniques yields that the utilization of the cathodoluminescence is highly suited for detecting small energy gap differences. Compared with the secondary electron contrast and the imaging by backscattered electrons, resp., it is clearly advantagoeus with respect to an identification specific tot he material. The course of the intensity profile with increasing primary electron energy permits to indicate a qualitative correlation with the value of the band gap. This is demonstrated with two heterojunctions with strongly different dopings. The Y-modulation technique is successful in displaying an orientation-dependent portion of the image contrast of homo- and heterojunctions of multiple structures.     

Zur Abschätzung physikalischer und physikalisch-chemischer Daten von AlBV-Verbindungen mit Zinkblendestruktur

The AlB^V-compounds display an exceptional position among A^IIIB^V-compounds regarding some properties which are related to the lattice constant. This behaviour is connected with the absence of core-d-electrons in Al. The compressibilities of AlP, AlAs and AlSb can be estimated from the lattice constant and the microhardness in fair agreement with calculated values. Relations between the lattice constants, molecular weight, some band structure parameters, the heats of formation and the surface energies are discussed. Phillips' ionicity parameter of AlSb is corrected and the bowing parameter of the energy gap of mixed AlB^V-compounds is calculated from the difference of the atomic radii of the substitutes.     

Computersimulation einer eindimensionalen polykristallinen Gefügebildung mit konstanter Keimbildungsrate und konstanter Kristallisationsgeschwindigkeit

For the process of isothermic freezing of a melt in a capillary tube with a constant nucleation rate and for all the crystallites with the same and constant rate of crystallization a mathematical model and computer programs for simulation are elaborated. In the result of simulation of the model by a digital computer one gets frequency distributions of the grain lengths. In a lot of simulated cases the cumulative frequency distributions of the grains could well be approximated by a Rosin-Rammler-Sperling distribution.     

Röntgenographische Untersuchungen zur Kristallperfektion von GaAs-Einkristallen und -Epitaxieschichten. Will Kleber zum Gedenken

The defect structure of bulk GaAs and homoepitaxial layers has been characterized by means of reflection methods of x-ray diffraction topography (doublecrystal topography, Berg-Barrett method) and in addition by rocking-curve measurements. Besides of dislocations, long-range distortions of the single crystals of GaAs are investigated and determined quantitatively. The measured widths of the rocking curves approach those expected for perfect crystals. Single and double twinning in growth hillocks on epitaxial GaAs is found in connection with a higher degree of imperfection. The perfection of single-crystal layers is similar to that of the bulk crystals. Based on contrasts observed in double crystal topographs and energetic discussions, statements are made one defect geometry of stacking-fault tetrahedra in epitaxial layers.     

Vergleich des Wachstums von Galliumarsenid aus Zinn mit dem Wachstum aus Gallium

By means of stationary liquid phase epitaxy it is shown that the kinetic inhibitions are strongly different for the growth of GaAs from Sn and Ga as solvents, respectively. These differences are responsible for the different growth morphology in both the systems. Values are given for the kinetic inhibition for the overgrowth of differently oriented GaAs seed crystals from Sn.     

Untersuchung dünner Isolatorschichten in Sandwich-Anordnungen mit dem Elektronenspiegel-Mikroskop

Characteristic image structures observed by investigations of Au–SiO_x–Ge sandwich systems using mirror electron microscopy are described. These image structures are caused by inhomogeneities in the conductivity of the insulating layer. An estimation of the dimension and the power of these inhomogeneities by the evaluation of the experimental results is possible.     

Zur Heteroepitaxie von AIBIIIC2VI-Verbindungen – Interpretation von RHEED-Diagrammen

Semiconductors of the A^IB^IIIC₂^VI type, crystallizing in the chalcopyrite structure, grow epitaxially with their {112}-planes on monocrystalline substrates with a three-fold symmetry of faces. It is shown that application of the RHEED technique permits definitively to decide what kind of epitaxial overgrowth takes place, supposing the atomic scattering factors of the I and III atoms are sufficiently different and/or the c/a axis ratio differs markedly from 2. CuInSe₂/GaAs and CuGaSe₂/GaAs show one-dimensional epitaxy     

Dünne Oxidschichten auf Eisenlegierungen,untersucht mit dem EF-Z6

At room temperature thinnest oxide layers develop on steel surfaces (in H₂O-free atmosphere). The conditions of their growth are discussed and compared with emission-electronmicroscopical observations.     

Zur Errechnung der Intensitäten von Auger-Übergängen für die quantitative Analyse von Festkörperoberflächen mit der Augerelektronenspektroskopie (AES)

According to an empirical equation for the Auger electron intensity arising from primary electron bombardment of solid surfaces, the parameters such as ionization cross section, relative Auger transition probability, backscattering factor and mean escape depth were evaluated for the L₃M₄₅M₄₅ Auger transition of elements with atomic number Z = 22 to 33. A comparison of the calculated relative intensities with experimental values from Palmberg et al. indicates a good agreement of both curves representing the intensity in dependence of atomic number. The mean relative deviation of calculated intensities from measured ones amounts to 20%. This is nearly the same value, as it has been estimated so far for the accuracy of quantitative AES without standard. Examining the influence of individual intensity parameters we were able to show that above all the ionization cross section and in the present case also the relative Auger transition probability determine the value of intensity.     

Zur Lamellenstruktur von Silizium-Kristallnadeln

Observations are reported on the lamellar structure of silicon needles with different forms of cross-section.     

Zur Bildung von Adsorptionsmischkristallen

By investigating the systems KCl-H₂O-impurity and NH₄Cl-H₂O-impurity the knowledge of the formation of Adsorptionsmischkristallen could be extended. Some specific properties of complex mixed systems are stated.     

Zur Realstruktur von Ga1–xInxAs LPE-Schichten

Ga_1–xIn_xAs epitaxial layers (0.02 ≦ × ≦ 0.12) are grown on (111)-oriented GaAs substrates from nonstoichiometric melts. The etch pit densities – determined by chemical etching – yield values between 2 · 10⁵ cm⁻² and 3 · 10⁷ cm⁻² and were found to be dependent on composition, layer thickness and cooling rate. X-ray topography of cleaved {110}-planes gives information on layer quality and indicates the existence of stress in the substrate lattice near the heterojunction. The validity of Vegard's law in the investigated concentration range was confirmed by X-ray determination of the lattice constants. The half width of double crystal spectrometer rocking-curves, the epd and the relative intensity of photoluminescence show similar dependence on the composition of the mixed crystal layers.     

Zur Lumineszenz von Zinksiliziumphosphid

Results of cathodoluminescene measurements of ZnSiP₂-single crystals grown by different techniques are reported. The luminescence excited in the various samples showed considerable differences in intensity and spectral position. These differences are apparently caused by the irregular incorporation of recombination centres in the present stage of crystal growth. Samples grown by “vapour phase technique with ZnCl₂” and by “spontaneous crystallisation from Sn or zn melt” showed line spectra typical for the special method of crystal growing. This relation between a typical line spectrum and the method of crystal growing chosen is attributed to the participation of intrinsic defects in the recombination processes. The detection of doping elements by means of luminescence measurements is discussed for ZnSiP₂ crystals doped by adding Te, Se, Ga. or In to the Zn melt.