摘要:

Thep, T, xdiagram of the Sn‐S system was determined especially in the region of the compound SnS. The pressure of S2in equilibrium with SnS and a liquid phase was found to extend over several decades up to 25‐mm Hg at the ``Sn‐rich'' side, whereas at the ``S‐rich'' side the S2pressures in equilibrium with solid SnS and a liquid phase lie between 25‐mm Hg and 100‐mm Hg. It was shown that the existence region of solid SnS very probably lies entirely at the excess sulfur side. The hole mobility in a plane perpendicular to thecaxis, ≈90 cm2/v sec at room temperature, was proportional toT−2,2for higher temperatures. The mobility in the direction of thecaxis was about five times smaller. Reversible annealing effects were found for temperatures above 200°C which could be explained by assuming association of neutral Sn vacancies. Absorption measurements showed that the edge absorption is due to indirect transitions. The bandgap was 1.08 ev at 300°K and 1.115 ev at 77°K. Interband transitions in the valence band were also found. The effective charge of the atoms (e*=0.7e0) and the effective masses of the holes in the three principal crystal directions (ma*=mb*=0.20m0;mc*≈m0) were determined from reflection measurements in the infrared. From these values and the value for the density of states mass obtained by means of the Seebeck effect (md*≥0.95m0), the number of equivalent maxima of the valence band was found to be at least four.

ISSN:0021-8979    

DOI:10.1063/1.1777047

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Measurements of Hall effect and resistivity up to 1300°K onp‐type hexagonal SiC showed an acceptor level for aluminium of 0.27 ev at zero donor concentration and a not yet identified acceptor level of 0.39 ev. The spin multiplicity of this unknown center appears to be four times smaller than that of the aluminium center, so that we may conclude that this unknown center in non‐ionized state has paired electrons. Taking a temperature dependence of the level depths proportional to that of the bandgap, the density‐of‐states effective mass of the holes amounts to 0.59m0. The Hall mobility shows at high temperatures the same temperature dependence as that ascribed to scattering of holes by optical phonons. Assuming that optical phonons really come into effect, the behavior of the Hall mobility in the temperature range from 1300° to 300°K can be explained taking also into account the effect of scattering by acoustical phonons and charged impurities. By a study of I–V characteristics of grown junctions in &agr;SiC and also by applying Roosbroeck‐Shockley's theory to the spectral distribution of thep‐nluminescence under forward bias, inhomogeneities were found over the junction area. By means of pyrolysis of gaseous compounds of Si and C pure crystals (4×2×2 mm3) of ``cubic'' &bgr;SiC were obtained. With the aid of polarized light the existence of a skeleton of a hexagonal twinning system was found in these crystals, the cubic SiC filling up the pores of this skeleton structure.

ISSN:0021-8979    

DOI:10.1063/1.1777048

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The ESR spectra of oxygen‐deficient and doped rutile have been investigated at liquid helium temperatures. Niobium and tantalum are shown to give rise to the donors Nb4+and Ta4+rather than Ti3+. The spectrum of reduced rutile depends on the method of reduction. Reasons for this are discussed. Under certain circumstances, involving hydrogen reduction, a particularly simple spectrum is observed. This degenerates and is replaced by a single line as the temperature is raised. A similar effect is obtained by increasing the concentration of centers. Possible assignments are discussed. Vacuum reduction results in distinctly different spectra which persist to higher temperatures. Resistivity measurements indicate a higher activation energy, by a factor of three, for vacuum‐reduced samples.

ISSN:0021-8979    

DOI:10.1063/1.1777049

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The contribution of free electrons to the refractive index and extinction coefficient of Ga‐doped CdS has been measured in a series of samples with carrier concentrations ranging from about 1017to 2×1019electrons/cm3. The effective massm* for electrons near the bottom of the conduction band was calculated from the free electron contribution to the refractive index and from the carrier concentration as determined from the Hall coefficient. The result,m*=(0.22±0.01)meis in satisfactory agreement with previous studies by other workers. The magnitude and wavelength variation of the absorption coefficient observed with about 1017carriers/cm3are in fair agreement with theoretical results calculated for a polar‐mode lattice scattering mechanism. Although similar data for 2×1018carriers/cm3are in good quantitative agreement with the impurity scattering theory at room temperature, the absorption for high carrier concentration is observed to decrease with temperature, in contradiction with the theory for a nondegenerate population. A theory for the degenerate concentration range is needed. Reflection and transmission of radiation polarized parallel and perpendicular to the crystalCaxis were studied for one sample. These data show (m⊥*/m∥*)=1.08±0.05.

ISSN:0021-8979    

DOI:10.1063/1.1777050

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The noncubic II–V semiconductors have been studied recently by several workers. A review will be given of the present situation. The energy gaps of these materials range from 0.13 to over 1 ev. Room temperature mobilities of 10–15 000 cm2/v sec have been observed. Anisotropy of electrical and optical properties have been reported for several of the compounds. For CdAs2it has been possible to explain the anisotropy of Hall mobility by a simple energy band model.

ISSN:0021-8979    

DOI:10.1063/1.1777051

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

HgSe single crystals are grown by zone melting. The compound crystallizes in the zinc‐blende structure and splits into (100) planes. For temperatures ranging from 90° to 500°K conductivity, Hall effect and thermoelectric power are measured; above 500°K evaporation of HgSe begins. The lowest carrier concentration of the crystals at 300°K is 3.5×1017cm−3. Onlyn‐type conduction is found. The highest mobility at 300°K is 18 500 cm2/v sec. Magnetoresistance shows that the longitudinal effect is very small compared with the transverse. From the photo emf of thep‐njunction Se/HgSe crystal and from the absorption edge of layers the energy gap of 0.5 to 0.75 ev is obtained. Using the temf and the absorption an estimation of the effective mass leads to 0.04 to 0.07m0.

ISSN:0021-8979    

DOI:10.1063/1.1777052

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Edge emission in single crystals of ZnSe subjected to ultraviolet radiation at low temperatures has been examined in the temperature interval from 4.2° to 77°K. Two distinct edge emission spectra have been found indicating that two different types of single crystals exist. For type I crystals the edge emission spectrum at 4.2°K contains 10 lines located between 4400 A and 4800 A; at 77°K the emission spectrum contains two lines. For type II crystals the edge emission spectrum at 4.2°K contains 14 lines located between 4400 A and 4900 A; at 77°K the emission spectrum contains three lines, one of which is located at the fundamental absorption edge of the crystal. Both crystal emissions show evidence of phonon interaction with the ZnSe lattice and both emissions undergo significant reductions in intensity as the crystal temperature increases from 4.2° to 77°K.

ISSN:0021-8979    

DOI:10.1063/1.1777053

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

HgTe1−xSexsolid solutions have been prepared, withxvarying from 0 to 1. The samples arentype nearx=1 andptype nearx=0, but, due to the high electron‐to‐hole mobility ratio, electronic conudction is dominant in the range 100–400°K in all samples. The concentration of free electrons lies between 5·1016and 3·1018cm−3. Measurements of the Hall mobility &mgr;Hand magnetothermoelectric effect &Dgr;Qshow that, for Se‐rich samples, lattice scattering is dominant in the range 77–400°K and that, near room temperature, &mgr;H∝T−2. For Te‐rich samples, lattice scattering is dominant in the range 200–400°K and, near room temperature, &mgr;H∝T−1. Effective masses have been calculated and it is seen that the conduction band is not parabolic. The detailed band structure and the exact value of the mobility seem to depend little upon structural factors. Forx=0.5 andx=0.9, the electron mobility can reach 12 000 cm2v−1sec−1at 293°K and 30 000 cm2v−1sec−1at 77°K.

ISSN:0021-8979    

DOI:10.1063/1.1777054

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A preliminary study has been made of the Righi‐Leduc effect in mercuric selenide (HgSe). The Righi‐Leduc magnetothermal effect is the thermal analog of the Hall effect wherein temperature plays the role of voltage and heat flow replaces electric current. The effect is particularly large in HgSe because of the coincidence of large electron mobilities (as high as 1.5 m2/v sec at 300°K) and low lattice thermal conductivity (about 0.02 w/°K cm at 300°K). Results are presented of measurements of the Righi‐Leduc coefficientSas a function of temperature, magnetic field strength, and electron concentration. Classically, for a one‐carrier material,S≅(&kgr;E/&kgr;)&mgr;, where &kgr;Eis the electronic, &kgr; is the total thermal conductivity, and &mgr; is the electron mobility. This expression is in qualitative accord with the experimental results. At room temperatureSranged between 0.27 and 0.34 m2/v sec for samples that had between 55×1017and 5.6×1017electrons/cm3.

ISSN:0021-8979    

DOI:10.1063/1.1777055

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Single crystals of ZnSe have been prepared by the vapor growth technique and optical and electrical measurements on these crystals are reported. Analysis of the reststrahlen reflection peak gives 0.026 ev for the transverse optical phonon energy. The longitudinal optical phonon energy is 0.031 ev as calculated from the transverse phonon energy, the static dielectric constant, &egr;0=8.1±0.3, and the high‐frequency dielectric constant, &egr;∞=5.75±0.1. The effective ionic charge calculated from the Szigetti formula is 0.7±0.1. Exciton absorption peaks associated with the valence and conduction bands in the vicinity of &Ggr; were observed at liquid hydrogen temperature with the principal peak at 2.81±0.01 ev. The exciton reduced mass 0.1m0combined with the room temperature electron‐to‐hole mobility ratio of 12, obtained by preliminary transport measurements onn‐ andp‐type ZnSe gives tentative values of 0.1m0and 0.6m0for the electron and hole masses, respectively.Reflectance was determined by various methods in the range 0.025 to 14.5 ev photon energy and was analyzed by the Kronig‐Kramers inversion method to obtain the optical constants in the 1 to 10 ev range. A number of peaks appear in the imaginary part of the dielectric constant.The first set of peaks, 2.7 and 3.15 ev, are believed to be due to exciton and interband transitions at &Ggr; with a spin‐orbit valence band splitting of 0.45 ev. The second set of peaks, 4.75 and 5.1 ev, are tentatively assigned to transitions atLwith a spin‐orbit splitting of 0.35 ev. Other peaks are observed at higher energies.

ISSN:0021-8979    

DOI:10.1063/1.1777056

出版商:AIP    

年代:1961

数据来源: AIP