摘要:

Effects of ultrasounds propagating perpendicular to the direction of a uniform dc magnetic field in degenerate semiconductors such asn‐type InSb have been studied by using a quantum treatment which is valid at high frequencies and in strong magnetic fields. It is found that the absorption coefficient and change in sound velocity oscillate with the dc magnetic field for the nonparabolic band structure. However, the absorption coefficient vanishes and no oscillations can be observed in the magnetic‐field dependence of the change in sound velocity for the parabolic band structure. The discontinuity in the frequency dependence of the change in sound velocity can only be observed in the nonparabolic band structure.

ISSN:0021-8979    

DOI:10.1063/1.329909

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A deep‐level defect distribution profiling system using both analog and digital data‐acquisition concepts is described. Analog circuits and digital data processing are used to provide high‐speed acquisition and a high dynamic range, respectively. The implementation has an advantage of easy adaptation with an existing deep‐level transient spectroscopy system having minimal software development. Additional advantages are the capabilities of eliminating long‐term system drifts and superposition of data taken subsequently for averaging in order to conveniently achieve a desirable signal‐to‐noise margin. Several examples using ion‐implantedn‐type andp‐type Si Schottky diodes are given. In addition, a metal‐oxide‐semiconductor field‐effect transistor after a Si+implant and annealing at 600 C is illustrated to indicate a high surface‐defect concentration due likely to the recoiling process.

ISSN:0021-8979    

DOI:10.1063/1.329965

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

We report calculations of the binding energy of an electron to a pair of charged donor ions in the presence of screening by free carriers. The effective‐mass approximation was assumed. We used a two‐dimensional finite‐element analysis to obtain numerical solutions, as we did in a previous study of the screening of single donor ions. The ground state was found to disappear into the conduction band at a doping level of 1.27×1019cm−3, at 300 K, with a uniform distribution of donors. The results support the conclusion that at doping levels of 2×1019cm−3or higher, the density of electronic states in silicon contains no contribution from localized bound impurity levels.

ISSN:0021-8979    

DOI:10.1063/1.329910

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Electronic properties of four defect centers (designated asE7,E8, I, and IV) in A1‐dopedn‐CdTe single crystals annealed under various Cd vapor pressures ( pCd) have been investigated by a combined use of photocapacitance, deep level transient spectroscopy (DLTS), and thermally stimulated capacitance techniques. Electron trapE7 atEc−0.68 eV, a dominant deep defect center in samples quenched after annealing under highpCd, has shown a strong interaction with the lattice vibrations (S≳30,S: electron‐phonon coupling parameter). The photoionization threshold energy for electronsE0nfor the purely electronic transition has been estimated to be larger than 1.30 eV. Temperature dependence of the capture cross section for electrons &sgr;tnhas been found to be very weak. The configuration coordinate diagram forE7 has suggested thatE7 will nonradiatively capture the free electron. On the other hand, recombination centerE8 atEc−0.74 eV, a dominant deep defect center in samples annealed under lowpCd, has shown only a negligible interaction with the lattice vibrations (S∼4) and has the photoionization threshold energies for electronsE0n( = 0.80 eV) and for holesE0p( = 0.95 eV) close to the thermal ionization energies for electronsEtn( = 0.74 eV) and for holesEtp( = 0.83 eV), respectively. The configuration coordinate diagram forE8 has revealed thatE8 can radiatively capture the free electron and the free hole and can emit photons of ∼0.66 and ∼0.75 eV, respectively.E7 andE8 have been proposed to be identical with the levels previously reported as the doubly ionized Cd interstitial and the doubly ionized Cd vacancy, respectively. As to true origins of these centers, the data obtained in this study have suggested that bothE7 andE8 may be donorlike complex centers including native defects, or impurities whose solubilities or stable sites in the lattice are strongly dependent onpCd. Hole trap IV atEv+0.48 eV, which gradually decreases in concentration with decreasingpCd, has shown a weak interaction with the lattice vibrations (S∼6.7). It has been revealed that level IV can capture the free electron with emission of the photon of ∼1.0 eV. This level has been attributed to an impurity whose solubility in the crystal is moderately dependent onpCd. Electron trap I, which exists only in samples quenched after annealing under the highestpCdand have an electron‐repelling barrier, has shown a very strong interaction with the lattice vibrations.

ISSN:0021-8979    

DOI:10.1063/1.329947

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Theoretical expressions are derived which describe the excess minority carrier distribution one can expect to observe when a Shockley‐Haynes measurement is performed in the presence of a contact. The contact has been modelled by postulating the existence of an interface recombination velocity (S) at the contact/semiconductor boundary. An ohmic contact (S= ∞) and the general case of a finiteScontact have both been considered. The variation in minority carrier distribution withSis illustrated using the derived expressions and the material parameters appropriate to a short wavelength (3–5 &mgr;m) Cadmium Mercury Telluride photodetector. The applied electric field (E) has been taken equal to 100 V cm−1and the width of the read‐out region,l= 40  &mgr;m. It has been shown that in this case an ohmic contact scarcely affects the average carrier distribution in the read‐out region, and therefore the ’’classical’’ theory can be applied to derive the mobility ( &mgr;) and diffusion constant (D), from the evolution with time of the conductivity modulation in the read‐out region. The same procedure, when applied to a less recombining contact, still leads to a fairly reliable value of &mgr;, but gives an appreciable overestimate ofD, due to the broadening of the observed pulse.

ISSN:0021-8979    

DOI:10.1063/1.329948

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Electrical conductivity of &agr; quartz is ionic, the current being carried by alkali ions (M+) moving in channels parallel to thecaxis. A study was made of conductivity &sgr; of one natural and three synthetic crystals in order to better understand these ionic defects. ac measurements were made over a wide range of frequencies, and complex‐impedance analysis was used to separate out the bulk conductivity from electrode effects. The activation energyEfor the synthetic crystals was always close to 1.36 eV and the pre‐exponentialAwas in the range of 106K/&OHgr; cm. A decrease in &sgr; resulted from electrodiffusion (sweeping) in hydrogen. For the as‐received natural crystal, the value ofEwas 0.82 eV, but thisEvalue increased appreciably after hydrogen sweeping or after irradiation plus high‐temperature anneal. The principal observations could not be interpreted in terms of the conventional theory in which the Al3+‐M+pair and its dissociation products are the only defects involved. A modified theory, in which additional unassociated Al is present as compensation either for H+or for oxygen vacancies, allows a detailed interpretation of the results. Supporting data are also obtained from infrared measurements.

ISSN:0021-8979    

DOI:10.1063/1.329949

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Following room‐temperature irradiation of quartz crystals by x rays or &ggr; rays, a transient enhancement of electrical conductivity is observed which decays over a period of several hours. This enhanced conductivity is produced by alkali ions (M+) which are liberated during the irradiation. By freezing in this transient conductivity of synthetic crystals to temperatures below 270 K, the activation energyEmfor migration of free alkali ions alongc‐axis channels of the crystal is shown to be 0.14±0.01 eV. The activation energy for the annealing process is ∼0.5 eV, showing that annealing is not controlled byEm. Results on natural crystals following irradiation are quite different from those of the synthetics; the differences are explained in terms of the presence of shallow traps for free M+ions in natural crystals. Finally, the transient conductivity is compared with other transient phenomena following irradiation, viz., the frequency change and internal friction of quartz‐controlled oscillators.

ISSN:0021-8979    

DOI:10.1063/1.329950

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The electrical properties of lightly doped polycrystalline silicon as a function of temperature have been investigated. The polycrystalline silicon was deposited by low‐pressure CVD and doped by phosphorus with ion implantation. TheI‐Vcharacteristic was measured over the temperature range of 20–300 K. Comparison was made between experimental data and an electrical conduction model including both thermionic emission and thermionic field emission at the grain boundaries. The grain boundary potential barrier height was found to be an increasing function of temperature below 300 K. The effect of geometrical size on the sheet resistance of these polycrystalline silicon resistors was also measured and discussed.

ISSN:0021-8979    

DOI:10.1063/1.329952

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Thermal depolarization current (TDC) and dielectric measurements of samples, M‐LC‐M, M‐SiO2‐LC‐SiO2‐M, and M‐PI‐LC‐PI‐M [LC = Liquid Crystal,p‐C5H11C(O)OC6H4C(O)OC6H4CN‐p, PI = polyimide, M = Cr and Al] have been carried out in order to investigate the behavior of charge carriers and the effects of insulating films used as blocking electrodes in liquid crystal cells. Electrode polarizations due to mobile ions contained in LC have been observed for the samples with bare and SiO2‐covered electrodes. The blocking ability of the evaporated SiO2layers exists under ac fields, but decreases with applied dc voltage. The SiO2has been also indicated to trap the ions formed near the electrode. On the other hand, an interfacial polarization between spin‐coated PI and LC has been observed for the samples having polyimide films on the electrodes. The polyimide layers have shown the blocking ability even under dc fields. The behavior of the TDC spectra will also be discussed in detail.

ISSN:0021-8979    

DOI:10.1063/1.329953

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Electrical transport coefficients were calculated for a thin, flat‐banded, nondegenerate semiconductor having spherical energy surfaces and a scalar isotropic effective mass. The conductivity, Hall coefficient, Hall mobility, and magnetoresistance were evaluated for a thin slab in terms of parametric integrals which were calculated numerically. The relaxation time of the bulk scattering mechanism was assumed to have a power law dependence on the carrier velocity. The surface scattering was assumed to be completely diffuse. The dependence of the transport coefficients on the thickness and magnetic field for a power index of one are displayed in graphical form.

ISSN:0021-8979    

DOI:10.1063/1.329954

出版商:AIP    

年代:1982

数据来源: AIP