摘要:

A probe having a spacially periodic potential is created by a bifilar winding of small tungsten wire. This geometry results in an electric field configuration having an extremely short penetration distance into the plasma. When the behavior of this probe is studied in extended negative glow and back‐diffusion type plasmas, the floating mode current‐voltage characteristic curve is seen to be quite different from that of the usual double probe in that no effects of the electrons are observed. The behavior of the periodic probe is controlled by the ion inertia established in the diffusion region which lies just in front of the probe. The important parameter of the characteristic curve is the slope near zero applied voltage difference which can be related in a simple manner to the flux of plasma diffusing to the probe and to the diffusion drift energy of the ions as they reach the probe. The electrons make no contribution to this slope for low applied voltage differences. This probe thus provides a very sensitive method for measuring the diffusive flux of plasma to a containing wall.

ISSN:0021-8979    

DOI:10.1063/1.1657385

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

An investigation of electron‐ and neutron‐produced defects in epitaxially grownn‐type (n≃2×1015cm−3) GaAs has been performed using Hall effect and electrical‐conductivity measurements. Electron irradiation (2 MeV) at 80°K decreases both the carrier concentration and the mobility. Below room temperature annealing of electrically active defects is observed near 250°K in agreement with thermal‐conductivity and length‐change measurements of electron‐produced defect annealing inn‐type bulk‐grown GaAs. An electron‐irradiation‐produced carrier removal rate of 2.9 cm−1at 80°K, an observed electronic energy level at ∼Ec− 0.14 eV, and a major annealing recovery stage near 500°K, are in reasonable accord with previous results from bulk‐grownn‐type GaAs. The accord between the present results from epitaxially grown GaAs and previous results from bulk‐grown GaAs suggests that crystal growth method does not play a dominant role in electrically active defect formation under electron irradiation. Neutron irradiation (approximately fission spectrum) at 76°K also decreases both the carrier concentration and the mobility inn‐type epitaxial GaAs. A light sensitivity of the carrier concentration and mobility is observed in GaAs after neutron irradiation. By analogy to Si and because disordered regions have been observed in electron microscope measurements on neutron‐irradiated GaAs, the neutron‐produced light sensitivity is ascribed to disordered regions. In contrast with electron produced defects in GaAs, neutron‐produced defects in the epitaxial layer exhibit only small and diffuse annealing throughout the 76°−600°K temperature range investigated. The mobility degradation after 400°K annealing is measurement‐temperature dependent and decreases with increasing measurement temperature between 76° and 300°K. The carrier removal rate, on the other hand, is nearly independent of measurement temperature and is 3.0 cm−1at 296°K. This carrier removal rate is in reasonable agreement with previous results on bulk‐grownn‐type GaAs irradiated at ∼375°K. Gunn effect oscillators are critically dependent upon carrier concentration, therefore carrier removal is expected to be the dominant failure mechanism for these devices under irradiation.

ISSN:0021-8979    

DOI:10.1063/1.1657386

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Lattice disturbances have been created in otherwise ``perfect'' ice single crystals by high‐energy neutron irradiation. These imperfections act as nucleation centers for internal melting when ir energy is absorbed. The interaction of a single neutron with the ice lattice is marked by one generated Tyndall flower which can easily be localized. A method is described to grow large single crystals of ice having the low concentration of imperfections necessary for the experiment. We also describe a Schlieren optical device with high resolution constructed for the observation of melting figures in the ice crystals.

ISSN:0021-8979    

DOI:10.1063/1.1657387

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Double injection currents are measured over the temperature range from 340° to 200°K with plane parallel metal‐semiconductor‐metal structures. It is shown that, in the absence of traps, the injecting junction limits the current at low operating points. The current‐voltage characteristics are analyzed considering the property of the injection contact.

ISSN:0021-8979    

DOI:10.1063/1.1657388

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A unified analysis of the current and conductance in metal‐insulator‐degenerate semiconductor tunnel junctions has been made by taking into account the nonparabolic momentum in the insulator. The current may either increase monotonically with voltages or exhibit a maximum at a voltage less than the Fermi energy of the semiconductor. For the conductance, a minimum always occurs at a voltage equal to or less than the Fermi energy and an additional pair of extrema may exist. The criteria for the various cases are established in terms of a set of reduced parameters of the junction. The effect of nonequal electron masses in the semiconductor and the insulator is also considered and shown to be important in determining the different shapes of the characteristics.

ISSN:0021-8979    

DOI:10.1063/1.1657389

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

It has been reported that room‐temperature Bi implants with no post‐implantation annealing produce high‐conductivityp‐type layers in ordinarilyn‐type CdS. We have similarly implanted Bi and also Xe into CdS at the 1015cm−2level, and have studied various properties including optical absorption, photoluminescence, and photovoltage. In all cases, similar behavior is observed with both Bi and Xe implants, which indicates that radiation damage effects are dominating any purely chemical effects.

ISSN:0021-8979    

DOI:10.1063/1.1657390

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

General expressions are derived for the excess carrier densities in the bulk of finite or infinitely extended panels of semiconductor materials under light excitation. The illumination is in the form of nonpenetrating rectangular or circular light spots partially covering the surface of the panel. Theoretical calculations reveal an appreciable change in excess carrier distribution as the illuminated region approaches the boundary of the material. Experimental results verify this effect and favorably compare with the theoretical calculations.

ISSN:0021-8979    

DOI:10.1063/1.1657391

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The detailed balance method of deriving the radiative‐recombination coefficient in semiconductors from the absorption curve is strictly applicable only when thermal quasiequilibrium exists for the carriers within each band. It is shown here that in many cases when the bands tail into the gap, the carriers are not in thermal equilibrium within the tail, even quite near the band edge, and that the detailed balance method requires modification. A simplified model, that of a regional bandgap variation, is suggested as an approximation to the complex band‐tailing situation. It is applied to measurements of photoluminescence and absorption inn‐type GaAs, of varying degrees of degeneracy, and values of the recombination constants at 296° and 77°K are derived. They are of the same magnitude as those in ideal material with no tailing. An uncertainty arises in degenerate material since it is not clear whether the reduced values of Burstein shift observed are entirely attributable to band shrinkage. The contribution of the deeper tail states to the luminescence often appears to be approximately independent of the separation of the state from the band edge.

ISSN:0021-8979    

DOI:10.1063/1.1657392

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A new versatile, coplanar‐contact device configuration has been developed for generation of coherent emission from indium antimonide. The devices, which generate coherent emission at frequencies from 6.5–30 GHz, exhibit three types of operation. Emission is generated (1) in a thin‐layer plasma formed by a strong transverse magnetic field, (2) in a thin‐layer plasma formed as a result of the coplanar‐contact configuration (zero magnetic field) and (3) in a thick‐layer plasma formed by forcing carriers away from the contact surface with a strong transverse magnetic field. For a resonance condition between the coplanar‐contacts, the emission frequency generated in a thin‐layer plasma is related to the contact spacing in accordance with two‐stream theory. The emission from the thin‐layer plasma in zero magnetic field and the noise emission generated at room temperature by the coplanar‐contact samples in a 10‐kG transverse magnetic field give further confirmation of the two‐stream theory. In the first and second types of operation, instantaneous power levels of 1 to 10 &mgr;W are emitted for input power levels of 0.2 to 1.5 W. In the third type of operation, with an input power level of 2 W, peak output power levels of 80 to 170 &mgr;W atX‐band frequencies have been measured. The low input power level, which is required for emission from the coplanar‐contact devices, permits cw operation in several samples. Low‐frequency instabilities generated in a thick plasma layer are frequency‐locked by a 160‐MHz external signal with a −3 dBm power level.

ISSN:0021-8979    

DOI:10.1063/1.1657393

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A nonisothermal analysis of dc conduction inn‐ andp‐type indium antimonide subjected to orthogonal electric and magnetic fields has been developed including the effects of energy‐dependent acoustic phonon and polar optical phonon scattering as well as minority carrier drift. Also, included are carrier generation, based on an equilibrium between carrier densities and particle temperatures, magnetoresistive effects and carrier injection. Threshold microwave emission curves are calculated assuming that a minimum minority carrier density is required to observe shot noise. The threshold curves give general agreement with the experimental results. When the distortion of the field due to the Hall effect is included, excellent agreement between theoretical and experimental curves is obtained.

ISSN:0021-8979    

DOI:10.1063/1.1657394

出版商:AIP    

年代:1969

数据来源: AIP