Sidney G. Parker

Characteristics of tunable Pb1−xSnx Te junction lasers in the 8–12‐μm region

The characteristics of tunable Pb1−xSnx Te (0.08⪝×⩽ lim ∼0.20) junction lasers are described. The lasers operate cw at liquid‐helium temperatures and for the above alloy compositions, the wavelength is in the 8–12‐μm region of the infrared. The devices are prepared by antimony diffusion into large p‐type vapor‐grown single crystals. Active region width, gain, and loss parameters are derived from measurements of the current density at the lasing threshold, efficiency, and cavity length dependence of the threshold current. Impurity diffused lasers favor oscillation in high‐order TE modes and some evidence of filamentary lasing was obtained from the device parameters together with a study of far‐field patterns. Results are presented which confirm the model of current tunability of these devices and provide data on refractive index and temperature dependence of the forbidden energy gap in these alloys. Finally, spectroscopic data are presented to show the present limitations and potential of the diode laser f...

Inhomogeneity model for anomalous Hall effects in n‐type Hg0.8Cd0.2Te liquid‐phase‐epitaxy films

Anomalous Hall effects, i.e., peaks in the temperature dependence of the Hall coefficient and Hall mobility, have been observed in liquid‐phase‐epitaxy (LPE) Hg0.8 Cd0.2Te films. After establishing that surface effects are not the cause of the anomalies and that our LPE films are indeed n type, we propose an inhomogeneity model with a network of extended p‐type inclusions in an n‐type matrix. Good fits to the experimental data have been obtained by computer simulation based on this model.

Epitaxial ZnSe on GaAs and Ge by HBr transport

Abstract The conditions for forming epitaxial deposits of ZnSe on Ge and GaAs substrates were determined for the ZnSe HBr H 2 , Zn Se HBr H 2 and Zn H 2 Se HBr H 2 systems. Laue topography showed that Zn H 2 Se HBr H 2 gave films of the greatest crystalline perfection, but the most rapid deposition rates were obtained with the ZnSe HBr H 2 system. Slower deposition rates did not always produce films of greater perfection, for crystalline perfection also was dependent on the reaction species. Deposition rates and crystalline perfection varied for different orientations. Films deposited on Ge substrates had greater crystalline perfection than those on GaAs substrates, but films on Ge substrates had a tendency to develop cracks. Doping with BBr 3 during deposition introduced donors in the ZnSe films and decreased the resistance of the films. Use of excess Zn during epitaxial growth with the ZnSe HBr H 2 system produced films having mobilities greater than 1000 cm 2 /V-sec at 300°K. Photoluminescence studies indicated that the luminescence centers in ZnSe are related to Zn and/or Se vacancies or interstitials.

Single crystals and epitaxial films of ZnSe by chemical transport

Single crystals of ZnSe up to 2 cm in length have been grown by iodine chemical transport with a 3–5°C thermal gradient. Dopants were introduced uniformly by this growth technique. Nonhomogeneous crystals of Zn(S, Se) were obtained by this method. Epitaxial growth of ZnSe on GaAs substrates by HBr transport was studied for various orientations. Use of excess Zn during deposition produced films having mobilities greater than 1000 cm2/V-sec.

Growth of large crystals of (Pb,Ge)Te and (Pb,Sn)Te

Large single crystals of Pb1-xGexTe (0 < × < 0.105) up to 10 g and Pb1-ySnyTe (0 < y < 0.26) up to 125 g were grown in sealed tubes by self-transport onto oriented single crystal seeds. The crystals were free of voids and inclusions, had dislocation densities as low as 103 cm-2, and were uniform in composition. Pertinent details of the growth technique, including thermal conditions, stoichiometry of the source, and seed orientation, are described. Results of evaluation of the crystals by metallography, Laue X-ray topography, and electron microprobe analysis are presented.

Terracing in HgCdTe LPE films grown from Te solution

Abstract Terracing in HgCdTe films grown by LPE from Te solution is influenced by many factors. These include melt-back of the substrate, substrate holder design, rotation rate of the substrate, thermal gradients, and growth rates. Many of the variables which influence terracing are interdependent and can be related to their effects on the supersaturation. Variables which tend to level the solute and/or thermal fields would tend to reduce terracing.

Improvements in the crystalline quality of PbxSn1−xTe crystals grown by vapor transport in a closed system

The quality of PbxSn1−xTe crystals to be used in infrared detectors was improved by elimination or reduction in the number of holes, linear voids, strains and dislocations during growth. This was accomplished by use of stoichiometric or slightly Te-rich charges preheat treated before use to reduce the number of holes. Linear voids and strains were reduced by using constant diameter growth tubes of 25 mm diameter. The number of dislocations was reduced by the use of a slow cooling rate and limited contract with the walls of the growth tube.

Determination of the liquidus-solidus curves for the system PbTe-GeTe

The liquidus and solidus curves for the PbTe-GeTe system were determined by DTA over the entire compositional range. The samples were annealed for one month at 600° C and rapidly quenched. X-ray data for the annealed-quenched samples indicated that solid solution exists across the entire compositional range. Unannealed samples indicated the presence of different phases.

Liquid phase epitaxial growth of Ca, Ge-Substituted garnet films having magnetic bubbles 1.0–3.0 μm in diameter

Abstract Ca, Ge-substituted, magnetic garnet films which would support bubbles of 1.0–3.0 μm diameter were grown by isothermal deposition frm supersaturated PbO-B 2 O 3 fluxes upon garnet films were yttriumm iron garnet Y 3 Fe 5 O 12 , in which rare earths substituted for yttrium and Ge substituted for Fe. Ca was added to charge compensate the Ge. A typical composition of a 2 μm bubble film might be Y 1.35Lu 0.3 Sm 0.6 Ca 0.75 Fe 4.25 O 12 , but the compositions of the films were varied by modifying the composition of the growth solution and the growth conditions. The magnetic properties of the films were dependent upon film perfection and composition. Bubble mobilities ranged ≈300–1000 cm/sec-Oe. The films, whose thickness varied from 1.0–3.0 μm to match buble diameters, were uniform in thickness to less than 0.30 μm across a 2.54 cm diameter slice. The properties of the films were sufficiently stable with temperature from 0–100°C to indicate that these materials could be used in memory devices.

Indium Antimonide of High Perfection

having mobilities at liquid nitrogen temperature of approximately with excess carrier concentrations in the 1013/cm3 range was produced by extensive purification steps followed by controlled crystal growth. The number of dislocations was less than 500/cm2 as revealed by etch techniques.