摘要:

Theoretical and experimental results are presented for the conductance peaks at the cyclotron harmonics in a plasma‐filled cylindrical capacitor. A theory is developed and is shown to predict peak height variation with density, harmonic number, and sheath thickness that is in agreement with experimental observation. A harmonic conductance peak is found to rise initially as density increases, only to fall to a minimum height as the upper hybrid frequency passes through that harmonic. Possible applications of this work to plasma diagnostics and further research are mentioned.

ISSN:0021-8979    

DOI:10.1063/1.1658511

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Measurements have been made of the current excited across Al2O3insulating barriers by proton bombardment. Films of Al2O3sandwiched between thin metal electrodes were bombarded by a monoenergetic beam of protons from a low‐energy accelerator. The Al2O3was grown by anodic oxidation on films of Al which had been deposited on glass substrates. The Al2O3films ranged in thickness from 100 to 600 Å. Ag counterelectrodes deposited on top of the Al2O3completed the junctions. The thickness of the Ag counterelectrode was <500 Å for all of the junctions studied. Current‐voltage characteristics of the junctions were measured while the junctions were in the proton beam. The current‐voltage curves were approximately linear, showing a net electron current from the Ag electrode to the Al electrode at zero bias, and zero electron current when the Al electrode was biased from 2.1 to 4.75 V negative with respect to the Ag electrode. Proton beam currents ranged from 5×10−10to 2×10−11A. Proton energies ranged from 26 to 102 keV. Results are interpreted in terms of a model in which the insulating film is represented by a potential barrier separating a sea of electrons on either side of the barrier. Conduction takes place by passage of excited electrons across the top of the barrier. The effect of the bias is to modify the internal electric field in the oxide and to shift the momentum distribution of the excited electrons. Time‐dependent effects in the current‐voltage curves are observed which are believed to arise from charging of the oxide by the proton beam.

ISSN:0021-8979    

DOI:10.1063/1.1658512

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Photoconductivity spectra taken on fast‐neutron‐irradiated samples of GaAs show a structure which is interpreted as being due to transitions between energy levels and either the valence or the conduction band. Levels lie at approximately 0.2‐ and 0.7‐eV above the valence band and 0.5‐eV below the conduction band. Slow‐neutron irradiation has been employed to compensate the acceptor impurity inp‐type GaAs. A level atEv+0.7 eV is detected in the high‐resistivity material thus obtained. It is concluded that such level is associated with a defect that is present in GaAs before irradiation in an inactive form.

ISSN:0021-8979    

DOI:10.1063/1.1658513

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Ohmic contacts under ambient conditions and at a low current‐density level may become blocking at a lower temperature and/or a higher current density. By observing the temperature dependence of the applied voltage across the sample for the two polarities under the constant‐current condition, the temperature dependence of the bulk and that of the barrier, if any, can be separated. The detection of the barrier, if the presence of the latter is relevant within the range of experimental interest, is easy and unequivocal. The technique is suggested for device physics studies in which the barrier may play a dominant role but nevertheless might escape detection under usual testing procedures. The method is applicable to the higher barrier‐height values as well as low. It also allows a simple study of the semiconductor effective mass through the determination of the Richardson constant.

ISSN:0021-8979    

DOI:10.1063/1.1658514

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The carrier distribution, space charge, and related quantities in a nondegenerate semiconductor are examined theoretically in rectangular Hall geometry with an applied magnetic field, and in cylindrical geometry with the self‐magnetic field only. Solutions in rectangular geometry are found for the special cases of zero and infinite recombination coefficient and for space‐charge conditions giving rise to constant and quadratic electric field configurations (symmetric recombination conditions). Solutions in cylindrical geometry are of zero order in the radius, i.e.,nandpare constant, but not the equilibrium values; the recombination coefficient is variable. The pinch gain,np/ni2, is determined essentially by the product of the transport numbers, the sum of the carrier mobilities, the magnetic permeability, the square of the axial current density, and the reciprocal of the recombination coefficient.

ISSN:0021-8979    

DOI:10.1063/1.1658515

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A simplified theory of Gunn domains is presented assuming a nonzero, but field‐independent diffusion coefficient. The simplification is achieved by using an approximate, analytic solution to a well‐known transcendental equation (the so‐called ``area integral'') of Butcher and Fawcett. Any further computer calculations, where necessary, then involve only simple quadratures of known analytic functions. For the piece‐wise linear approximation to theV(F) vsFcurve the entire program can be carried out analytically with the aid of the Regional Approximation method. The use of dimensionless variables brings out the central role, in Gunn domain theory, of the critical dimensionless parameter &agr;=&egr;FTVT/eN0D, withFTthe threshold field,VTthe threshold drift velocity,N0the thermal‐equilibrium free‐carrier density andDthe diffusion coefficient (mks formula). For GaAs, &agr;≈4×1015/N0withN0in cm−3. A particularly simpleV(F) vsFcurve is proposed for the study of phenomena (e.g., impact ionization across the gap) deriving from very high‐field Gunn domains. A complete analytic study is made of the Gunn domains associated with this special characteristic.

ISSN:0021-8979    

DOI:10.1063/1.1658516

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A luminescence study was made of Sn‐, Te‐, or Zn‐doped AlxGa1−xAs in the Al‐rich composition range where the bandgap transition is indirect. Several luminescent bands attributed to excitons, free‐bound carrier and donor‐acceptor recombinations have been observed. The experimental data are consistent with an ``optical'' ionization energy of Sn and Te donors in the range of 59±7 meV, and 56±5 meV for Zn acceptors. These values are expected to be similar in AlAs.

ISSN:0021-8979    

DOI:10.1063/1.1658517

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

A numerical solution based on the general equations of conduction and recombination is used to calculate the current‐voltage characteristics ofp‐``i''‐ndiodes in which the ``i'' region contains multivalent trapping centers. The theory is based on the assumption that the current is entirely field driven in the ``i'' region. The solution includes calculation of important properties of the conduction mechanism, such as the space charge and carrier density distributions. The results are a considerable improvement over more approximate analytical solutions, since the present method allows for important effects such as variations in the carrier lifetimes with injection level. Calculations are presented for the case of the Zn impurity in Si and are compared with previously published results for Au in Si. We discuss a space‐charge neutrality approximation which gives reasonable agreement with the exact calculations for certain ranges of theJ‐Vcharacteristic and which provides useful insight into the conduction process in thep‐``i''‐n. Comparisons are made between the present work and previous theoretical models based on more restrictive approximations.

ISSN:0021-8979    

DOI:10.1063/1.1658518

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

Highly sensitive magnetic effects on the voltage‐current characteristics in a longp+‐&pgr;‐n+diode biased forwardly are analyzed. The solutions of this analysis are consistent with the following assumptions: The similar treatment for the Righi‐Leduc effect, which is produced by the varied effect of the magnetic field on hot and cold carriers, is also applicable for the case where there is a density gradient in the sample. In addition, since the diffusion current and the effect of surface recombination are small enough to be neglected, the current flows through only the volume‐recombination process. The major results are as follows: (1) Highly sensitive magnetic effect in ``double‐injection regime'' mainly depends on the recombination process for the injected electrons which are minority carrier. This differs from the effect in ``Ohmic regime'' where majority carrier contributes to the current. (2) The threshold voltage, at which the negative resistance occurs, is strongly dependent on a ratio of the recombination densityNRto the majority carrier densityp0. (3) The currentJin the double‐injection regime beyond a minimum voltage follows aJ∝V2+slaw, wheresis a function of the mobility ratiob, and it is given ass≈2(blog2−1).

ISSN:0021-8979    

DOI:10.1063/1.1658519

出版商:AIP    

年代:1970

数据来源: AIP

摘要:

The spectroscopic features of crystals of the scheelite‐structure lithium yttrium fluoride (LiYF4) doped with Nd3+and Yb3+have been measured at 300°K. The energy‐transfer properties of Nd3+→Yb3+in this host have been studied and compared with other materials possessing the scheelite structure.

ISSN:0021-8979    

DOI:10.1063/1.1658520

出版商:AIP    

年代:1970

数据来源: AIP