摘要:

A theoretical investigation of the diffusivity of holes in Si as a function of temperature, field strength, and field direction is reported. Calculations have been performed with the Monte Carlo procedure. The theoretical analysis explains the main features exhibited by the experimental data available from the literature. Minor discrepancies between theory and experiment are discussed in terms of microscopic mechanisms and/or reliability of the different experimental techniques used.

ISSN:0021-8979    

DOI:10.1063/1.336507

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A method has been developed to obtain, by means of charge‐collection microscopy (CCM), a calibrated two‐dimensional map of the electrical activity of the minority carriers in a semiconductor crystal over large crystal dimensions. This is achieved by the calibration of the collection current in terms of the minority‐carrier diffusion length and a photographic gray scale. The technique is applied to plastically deformed silicon and proves that it has great potential for the evaluation of electrical activity mechanisms in imperfect silicon.

ISSN:0021-8979    

DOI:10.1063/1.336508

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Boltzmann’s transport equation was solved using a variational method (including all major scattering mechanisms and screening) yielding electron mobilities inn‐ZnSe. The electron concentration dependence of the mobility at 300 and 77 K was calculated as functions of ionized impurity concentration and compensation ratio. A routine method for determining acceptor and donor densities (total and ionized) and compensation ratio from given experimental mobility and carrier concentration values is outlined; mobilities reported for samples grown by various techniques are discussed. Inherent limits to the mobility are given as about 800 cm2/V s (n∼3×1018cm−3) and about 1×104cm2/V s (n≤4×1015cm−3) at 300 and 77 K, respectively. The calculated temperature dependence of the mobility for &eegr;=−6 is used to explain qualitative trends in such behavior for material grown by different techniques, and to provide an inherent mobility limit at this &eegr;.

ISSN:0021-8979    

DOI:10.1063/1.336509

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The penetration depths of protons in the (0001¯) face of ZnO produced by 100‐ and 400‐eV hydrogen‐ion bombardment are studied by three methods: calibrated argon‐ion sputtering, calibrated etching, and space‐charge capacitance measurements in the ZnO/electrolyte system. For the 100‐eV implantation, the latter method provides unequivocal support to our previous conclusion that the protons, acting as fully ionized donors, penetrate only to a depth of 10–20 A˚ below the surface. The narrow space‐charge layer so produced, having surface electron densities of up to 2 × 1014cm−2, constitutes a quantized, two‐dimensional electron gas system. In the 400‐eV implanted surface, the proton penetration depth is considerably larger. In this case an approximate depth profile could be derived from the combined measurements. It consists of a Gaussian distribution, peaked about 40 A˚ below the surface with a standard deviation of some 80 A˚. However, some 10% of the implanted protons are found to penetrate much deeper, being distributed up to 1000 A˚ or more below the surface. For 100‐eV implanted surfaces, similarly large penetration depths were observed, but the percentage of the deep lying protons is less than 1%. Such huge penetration depths arise most probably from a channeling mechanism.

ISSN:0021-8979    

DOI:10.1063/1.336510

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The complex admittance of ann‐type Hg1−xCdxTe/Photox SiO2interface withx=0.3 has been examined for frequencies ranging between 1 mHz and 4 MHz. The conductance method is used to decompose the total interface state density into three types of components: a valence‐band tail, a conduction‐band tail, and some well‐resolved discrete states. The fixed charge density is low and there is no statistical broadening. The surface valence‐ and conduction‐band edges are both found to be shifted upward in energy relative to their respective bulk values; moreover, the surface has converted toptype. The energy variation of the valence‐band tail states response times follows a pattern characteristic of Shockley–Read recombination centers with a constant capture cross section, but the behavior of the conduction‐band tail states is more complicated. Evidence is presented that the interface region has a higher Cd concentration than the bulk.

ISSN:0021-8979    

DOI:10.1063/1.336511

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The barrier heights of the electrodepositedn‐type CdTe thin‐film metal semiconductor (MS) and metal‐thin insulating layer‐semiconductor (MIS) devices have been measured by internal photoemission. The data for both MS and MIS devices can be fit with the square root of the photocurrent per absorbed photon dependence consistent with the Fowler theory. The barrier height of Ni‐CdTe is 0.75 eV at room temperature, and its temperature dependence is about the same as that of the CdTe band gap. This suggests that the barrier height is pinned with respect to the CdTe valence band edge. Oxidation in air at 300 °C for an hour produces a layer of about 25 A˚ or TeO2on the CdTe surface. Thicker oxide can be grown for longer oxidation time. Negative oxide charges are found in some devices. At room temperature, the barrier height of Ni‐TeO2‐CdTe is 0.92 eV. As temperature is decreased, the barrier height increases and its rate of change with temperature is less than that of the CdTe band gap. Samples stored in room atmosphere show aging effects, one of which is the increase in surface‐state density. The dips in the curve of the spectral dependence of the relative photon‐induced current are caused by electrons which drift to the metal after being photoexcited from occupied surface states below the Fermi level. These dips correspond to peaks in the energy distribution of the surface state density. At zero bias and 170 °K, four peaks at 1.02, 1.06, 1.18, and 1.26 eV are observed for the MIS devices. For the MS devices zero biased at room temperature, four peaks at 0.85, 0.94, 1.02, and 1.05 eV are observed. The magnitudes of the dips at 0.85, 0.94, 1.18, and 1.26 eV vary with bulk‐defect density and these levels shift towards higher energy as temperature is decreased. On the other hand, the levels at 1.02 and 1.05 eV for the MS devices and 1.02 and 1.06 eV for the MIS devices are independent of temperature and bulk defect density.

ISSN:0021-8979    

DOI:10.1063/1.336512

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We present the results of a comprehensive series of measurements on glow‐discharge (plasma) ‐deposited silicon nitride films SiNx:H, withxin the range 0<x<1.2. Optical spectroscopy in the visible and infrared regions is used to investigate the nature of the bonding and to assess the role of hydrogen. With increasingx, in the rangex<0.7, an increase in the concentration of Si‐H bonds results in an increase in the total hydrogen content; at higherxthe rise in the N‐H concentration produces a small increase in the hydrogen content, but even for these samples most of the hydrogen is bonded to silicon. The optical absorption edge due to band‐gap transitions broadens with increasingxdue to a change in the nature of the valence band from Si‐Si bonds to N lone‐pair states. Electrical conductivity at high fields and magnetic resonance measurements give information about the defects in the band gap. These results support the Robertson–Powell model in which the principal defect in the band gap of silicon nitride is the silicon dangling bond.

ISSN:0021-8979    

DOI:10.1063/1.336513

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Thin films of ZnTe and Cd1−xZnxTe (x<0.5) have been deposited by the direct combination of the elements on the surface of W/graphite, ceramic, and glass substrates at 550–600 °C in a hydrogen or helium atmosphere. Their microstructure, crystallographic, optical, and electrical properties were studied. Because of the greater stability of ZnTe than CdTe, the Zn/Cd molar ratio in Cd1−xZnxTe films is always less than that in the gas phase. The optical band gap of ZnTe has been determined to be 2.25 eV and that of Cd1−xZnxTe is a linear function of the composition. Preliminary work on Cd1−xZnxTe /CdS heterojunctions has also been carried out.

ISSN:0021-8979    

DOI:10.1063/1.336514

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Transient capacity measurements between 77 and 300 K were performed to study the relaxation of optically induced inversion layers in metal‐insulator‐nsilicon structures with 23–176‐A˚ oxide thickness. The observed fluence of the charge in interface and inversion layer exhibits as a function of time three distinct maxima. A theoretical study of the two governing nonlinear differential equations—Shockley–Read–Hall recombination in interface traps, and continuity equation for holes in the valence band—shows that the first peak is caused by recombination in silicon‐bulk traps while the second and third peaks are generated by tunneling recombination in interface traps. A quantitative analysis of the data shows satisfactory agreement between experiment and theory.

ISSN:0021-8979    

DOI:10.1063/1.336515

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Praseodymium bromate was prepared from Pr2O3and the single crystals of Pr (BrO3)3 ⋅  9H2O were grown. The principal magnetic susceptibility &khgr;⊥and the anisotropy &khgr;∥‐&khgr;⊥was measured in the range 300–90 K. The variation of the average magnetic momentpeffwith temperature is appreciable showing a deviation from the Curie law. The magnetic anistropy &khgr;∥‐&khgr;⊥is found to be much higher than in Pr‐ethylsulfate where the Pr3+ion occupies a site very similar to that in PrBR. A crystal field analysis with a field ofD3hsymmetry is found to provide an excellent account of the magnetic properties observed by us and Simizuetal. [J. Appl. Phys.55, 2333 (1984)] from 300 K down to ∼0.06 K. The Hamiltonian was diagonalized in the complete basis of the3H ground term taking care of the intermediate coupling effects to a large extent. Some important predictions on the electronic heat capacity and the electric quadrupole splitting have been made. An estimate of the crystal field parameters has been made using the available structural data on the crystal and the results are discussed in the light of our phenomenological set of parameters.

ISSN:0021-8979    

DOI:10.1063/1.336516

出版商:AIP    

年代:1986

数据来源: AIP