ISSN:0021-8979    

DOI:10.1063/1.1777005

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

In discussing the galvanomagnetic effects of semiconductors with high electron mobility one has to distinguish four main groups of parameters which influence these effects: (1) For InSb with practically no magnetoresistive effect on a long rod, an increase in resistance by a factor 38 can be reached in 10 000 gauss with appropriate shape (field disk). (2) Layers periodically changing their electron concentration produce an anisotropy of magnetoresistance. For certain specimen orientations the Hall coefficient depends on the magnetic field and a planar Hall effect is observed. Near a step of concentration one measures apparent negative resistances which are caused not by a retrograde current, but merely by rotation of the current lines. (3) If there are more than one type of charge carriers, it is difficult to know the concentration and mobility characteristic of a special type. Because of the high mobility ratio in InSb it is possible to state a hole mobility of 620 cm2/v sec in 150 000 gauss for pure material at room temperature. (4) After elimination of the influences of the above‐mentioned points 1 to 3 one cannot find in InSb any magnetoresistive effect of electrons in the conduction band up to 150 000 gauss. The Hall coefficient is magnetic field independent up to this value of the magnetic induction forn‐type InSb.

ISSN:0021-8979    

DOI:10.1063/1.1777018

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Most samples of GaAs show properties similar to those of germanium and silicon, but it is possible to prepare GaAs with a resistivity at room temperature greater than 106ohm‐cm, and the electrical properties are then more like those of the wide band gap II–VI compounds, such as CdS. This form of material, known as semi‐insulating GaAs, previously has not been studied thoroughly, partly because homogeneous samples were not available.Measurements have now been made on semi‐insulating GaAs, and results are reported for carrier concentration and mobility as a function of temperature. The interpretation of the results is sometimes complicated because even at room temperature the activation energy is about half of the intrinsic activation energy, and the carrier concentration can be close to the intrinsic concentration.The dominant lattice scattering mechanism in GaAs is believed to be polar scattering, but even in the purest samples of semiconducting GaAs made thus far, impurity scattering is observed at room temperature. In a highly compensated material like semi‐insulating GaAs, neither the Brooks‐Herring nor the Conwell‐Weisskopf theory of impurity scattering is likely to be valid. An initial study of carrier scattering has been made using measurements of transverse magnetoresistance and the field dependence of Hall coefficient. Some values for carrier lifetime are also reported.

ISSN:0021-8979    

DOI:10.1063/1.1777019

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The effect of hydrostatic pressure on the transport properties ofn‐type GaSb, InP, GaP, andp‐type PbTe was measured to study their band structure. (1) The Seebeck coefficient, Hall coefficient, and resistance of threen‐GaSb samples were measured as a function of hydrostatic pressure up to 17 000 atm between 200° and 400°K. The Seebeck coefficient &agr; increased with pressure and approached a constant value at about 10 000 atm. The saturation value of &agr; does not follow the simple32lnTrelation for any of the samples; e.g., for a sample withRH(77°K) ≈95 coul−1cm3, the saturation value of &agr; decreases with temperature. The contribution due to the phonon‐drag effect has been considered as a possible explanation for this phenomenon. (2) The conductivity ofp‐PbTe increased almost exponentially with pressure both at 300° and 194°K; the Hall coefficient at 300°K decreased by about 5% at 8000 atm, while the conductivity increased by 55% at this pressure. (3) The resistance ofn‐InP samples increased with pressure; the pressure coefficient was found to be bigger for samples with higher impurity contents. (4) The resistance of ann‐GaP sample decreased by about 3% at 10 000 atm.

ISSN:0021-8979    

DOI:10.1063/1.1777020

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Measurements of the voltage and temperature dependence of tunneling in Ge and GaSb are presented which confirm the close proximity of the (000) and (111) conduction band edges in these materials. In the case of Ge, the energy separation of these edges is found to increase with increasing donor concentration.Tunneling in the indirect semiconductor GaP shows no evidence for indirect (phonon‐assisted) tunneling transitions. It is believed that tunneling in the junctions which we studied proceeds via deep‐level impurities rather than between conduction and valence bands directly, thereby eliminating the requirement of wave number conservation.Revised values for the zone‐center longitudinal optical phonon energies as deduced from tunneling data in 3–5 and lead salt semiconductors are presented.

ISSN:0021-8979    

DOI:10.1063/1.1777021

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Three types of conduction band extrema in the (000), (100), and (111) directions inkspace seem to determine many of the properties of the group 4 and group 3–5 semiconductors. Early experimental work on the pressure coefficients of the energy separations of these extrema from the valence band maximum energy, carried out on Ge (111), (000), (100), Si (100), and InSb (000), suggested that the three pressure coefficients might be independent of the specific element or compound in the group 4 and group 3–5 series. This work is discussed in detail, and the theoretical basis is briefly considered. All of the completed pressure measurements on these compounds are critically reviewed, and the correlation of unique pressure coefficients with specific band edges examined. It is demonstrated that pressure experiments can be planned to show up details of the band structure unavailable for study at atmospheric pressure. Particular attention is paid to GaP, and a new model for excess absorption occurring inn‐type samples of this compound and in Si, GaAs, and AlSb is suggested. The application of similar techniques to PbS, PbSe, and PbTe is discussed, and results of electrical and optical measurements of energy gap and electron and hole mobilities presented.

ISSN:0021-8979    

DOI:10.1063/1.1777022

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Resistivity, Hall coefficient, and magnetoresistance were studied forn‐ andp‐type GaSb. The infrared absorption edge was investigated using relatively purep‐type, degeneraten‐type, and compensated samples. Infrared absorption of carriers and the effect of carriers on the reflectivity were studied. The magnetoresistance as a function of Hall coefficient forn‐type samples at 4.2°K gave clear evidence for a second energy minimum lying above the edge of the conduction band; the energy separation is equal to the Fermi energy for a Hall coefficient of 5 cm3/coulomb. The shift of absorption edge inn‐type samples showed that the conduction band has a single valley at the edge, with a density‐of‐state massmd1=0.052m. By combining the results on the edge shift, magnetoresistance, and Hall coefficient, it was possible to deduce: the density‐of‐states mass ratiomd2/md1=17.3, the mobility ratio &mgr;2/&mgr;1=0.06, and the energy separation &Dgr;=0.08 ev between the two sets of valleys at 4.2°K. Anisotropy of magnetoresistance, observed at 300°K, showed that the higher valleys are situated along (111) directions. The infrared reflectivity ofn‐type samples can be used to deduce the anisotropy of the higher valleys; tentative estimates were obtained. Infrared reflectivity gave an estimate of 0.23mfor the effective mass of holes. The variation of Hall coefficient and transverse magnetoresistance with magnetic field and the infrared absorption spectrum of holes showed the presence of two types of holes. Appreciable anisotropy of magnetoresistance was observed in ap‐type sample, indicating that the heavy hole band is not isotropic; this was confirmed by the infrared absorption spectrum of holes. The results on the absorption edge in various samples seemed to indicate that the maximum of the valence band is not atk=0. However, it appears likely that transitions from impurity states near the valence band produced absorption beyond the threshold of direct transitions.

ISSN:0021-8979    

DOI:10.1063/1.1777023

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A series of detailed measurements of the lattice absorption bands of gallium arsenide has been made over the wavelength range 10–40 &mgr; and over the temperature range 20–292°K. These results can be interpreted in terms of multiple phonon interactions involving five characteristic phonon energies. These results, along with the known elastic constants, have enabled us to supply all the relevant data for a computation of the complete phonon spectrum using an extension of the shell model.

ISSN:0021-8979    

DOI:10.1063/1.1777024

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The influence of various structural characteristics in the III–V compounds on galvanomagnetic properties is discussed. Evidence for the scattering of charge carriers by polar optical modes is reviewed, and the behavior of Hall and magnetoresistance coefficients is examined in regard to the conduction band structure. Unique characteristics, imparted by light masses in certain bands, include high mobilities and large magnetoeffects associated either with transport in the band or with ionization energies of the impurity centers. The importance of avoiding inhomogeneities, either in specimen or in magnetic field, when measuring Hall coefficient or magnetoresistance in high‐mobility materials is emphasized. Illustrations are given of the effects of nonuniformities in carrier concentration or in applied magnetic field on various galvanomagnetic phenomena.

ISSN:0021-8979    

DOI:10.1063/1.1777025

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Magnetoreflection experiments involving both intraband and interband transitions can provide valuable information about the electronic band structure of semiconductors. In the intraband experiments, performed near the plasma reflection edge, the application of a magnetic field splits the edge and results in the formation of two minima separated by the cyclotron frequency. It is thus possible to determine the cyclotron frequency directly, at room temperature, and for high carrier concentrations. When scattering losses are taken into account in the theory, it becomes possible to determine the carrier concentration, scattering time, and effective mass from the optical measurements alone. The theory of the effect is discussed for applied magnetic field transverse and parallel to the direction of propagation, and experimental results are presented for InSb, InAs, and HgSe. A consistent fit to Kane's theory for the variation of mass with concentration in InSb is obtained when previously published data have been corrected for reststrahl dispersion.Interband magnetoreflection experiments can be useful in cases where high absorption coefficients or difficulty of preparing thin samples make transmission experiments unfavorable. This type of experiment yields information on energy band gaps, effective masses, andgfactors. Experimental data for the direct transition in InSb are presented.

ISSN:0021-8979    

DOI:10.1063/1.1777026

出版商:AIP    

年代:1961

数据来源: AIP