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1.
The presence of parts per million (ppm) levels of impurities in the low-temperature arsenic charge used in molecular beam epitaxy (MBE) is shown to have a dramatic effect on the quality of GaAs grown. Source charge impurities play a vital role in determining the apparent variation in reported doping behaviour in MBE:GaAs.  相似文献   

2.
This paper is concerned with the optimization of growth conditions for a-Si1-x Ge x :H alloys. It is shown that H-dilution of source gases selectively improves the band transport of electrons without significantly affecting the recombination center density or the band transport of holes. It is further shown that the beneficial effects of H-dilution are most pronounced in alloys with comparable densities of Si and Ge.  相似文献   

3.
The experimental method used in this work is based upon the idea of nonavalanche injection of carriers heated by direct electric field. The structure consisted of an n-channel MOS transistor and two p-n junctions. The process of charge injection in this structure was investigated by studying the dependence of gate current on heating voltage. The trapping properties of the SiO2 film were studied by monitoring the charging of the film during injection of electrons. The capture cross-sections, the trap centre concentrations and the dependence of the capture cross section on the electric field for fields between 1 MV/cm and 2.5 MV/cm were determined.  相似文献   

4.
Electrical properties of Fe2O3 were studied by using several electrical methods such as electrical conductivity, thermopower (Seebeck effect) and work function. The studies were performed at elevated temperatures (1053–1153 K) and under controlled oxygen activity (102105 Pa). Samples of different thickness varying between 103 nm and 1 mm were taken for the measurements of both electrical conductivity and thermopower. It has been found that the exponent of the po2 dependence resulting from the work function measurements (1/n ) is about 1/2. Both thermopower and electrical conductivity data are well consistent with work function data for the thin film (1000 nm) of Fe2O3. The charge transport in Fe2O3 has been interpreted in terms of small polaron mechanism. Analysis of measured electrical parameters, regarding the thickness of studied specimens, indicates that the near-surface layer of Fe2O3 exhibits much higher deviation from stoichiometry than the bulk phase and resulting strong interaction between charge carriers. This effect has been interpreted in terms of segregation of intrinsic lattice defects to the surface, and presumably also to grain boundaries, of Fe2O3.  相似文献   

5.
The effect of In content on do electrical conductivity and DTA of the system (As2Se3)1-x. Inx, x=0, 0.01, 0.05, has been studied. The electrical energy gap was found to increase for an In content 0.01% and decrease for an In content 0.05%. The samples exhibit the three conduction mechanisms proposed by Mott and Davis. The activation energy was calculated for each mechanism. The effect of heating rate on the transition temperatures (T g,T c,T m) was studied and the variation of the crystallization-peak position was used to calculate the activation energy and the order of the crystallization process.  相似文献   

6.
The specific luminescence process in GaAs doping superlattices arises from recombination of electrons populating low-index conduction subbands with holes in the acceptor impurity band across the indirect gap in real space. The luminescence peak energy thus directly reflects the actual value of the tunable gap for the photoexcited state of the superlattice. We have studied the tunability of the effective gap, the recombination rate, and the relative quantum efficiency on superlattice specimen of different material design parameters by means of low-temperature photoluminescence measurements. For optimized design parameters the ratio between luminescence and excitation intensity remains nearly constant over the entire tunability range of the effective gap.  相似文献   

7.
A spectroscopic analysis by the light-beam-induced-current technique has been carried out to study the electrical properties of stacking faults in Czochralski silicon subjected to internal gettering treatments. By changing the wavelength of the light beam probing the sample, we have obtained the depth profiling of the stacking fault electrical activity. Occurrence of minority carrier recombination and generation processes at some stacking faults, corresponding, respectively, to dark and bright levels in a grey-shade imaging, has been observed. The presence of fixed charges at the defect-silicon matrix interface is hypothesized as a possible cause of the observed images.  相似文献   

8.
The kinetics of the Staebler-Wronski effect ina-Si:H were investigated experimentally. The rate of recovery from the illuminated state B to the annealed state A was observed at various temperatures in undoped,n- andp-dopeda-Si:H. The data can be characterized by a thermally activated relaxation time with an activation energy decreasing with increasing doping concentration. The results are compared with previous data and existing models.  相似文献   

9.
Hall effect and resistivity measurements in silicon doped indium selenide (InSe), from 7K to 500K, are reported. Results are interpreted through a model, previously proposed for tin doped InSe, that takes into account the contribution of both three- and two-dimensional electrons to charge transport along the layers in InSe.  相似文献   

10.
A fluctuation transport theory is applied to describe the mobility limiting effect of interface roughness scattering in semiconductor heterostructures. As an example we consider a high mobility transistor and compare electron scattering by interface roughness with Coulomb scattering processes by ions and dipole fluctuations. We show that the dynamical resistivity measurement provides detailed information about the autocorrelation of the interface morphology.  相似文献   

11.
12.
Hall effect, DLTS and low-temperature photoluminescence measurements were used to study the effect of dimeric (As2) vs tetrameric (As4) vapour species on the electrical and optical properties of nominally undoped and of Ge-doped GaAs layers grown by molecular beam epitaxy (MBE). The arsenic molecular beam was generated from separate As2 and As4 sources, respectively, and from a single source providing an adjustable As2/As4 flux ratio. The occurence of the previously described defect related bound exciton lines in the luminescence spectra at 1.504–1.511 eV was found to be directly correlated with the presence of three deep states (M1, M3, M4) which are characteristic of MBE grown GaAs. The intensity of the extra luminescence lines and simultaneously the concentration of the deep electron traps can be reduced substantially simply by decreasing the As4/As2 flux ratio. The incorporation of defect related centers as well as of amphoteric dopants like Ge strongly depends on the surface chemistry involved. Therefore, a considerably lower autocompensation ratio in Ge-dopedn-GaAs is obtained with As2 molecular beam species which provide a higher steady-state arsenic surface population.  相似文献   

13.
14.
Acceptor doping of MBE grown Ga0.47In0.53As on InP:Fe substrates utilizing manganese is investigated as an alternative for overcoming problems related to beryllium doping. The incorporation behaviour of manganese is analyzed in detail with respect to its application in optoelectronic device structures. Special emphasis is put on low-level and maximum-level doping relevant for use in buffer and contact layers, respectively. The dependence of activation energy and the degree of ionization on acceptor concentration is determined. At high doping levels the free-hole concentration is markedly lower than the doping concentration. It is attributed to the diffusion of acceptor species across the heterointerface into the substrate. Manganese diffusion is demonstrated to be an important effect for the interpretation of the measurement results. Manganese doping is applied in p+/n/p-layer structures for junction field effect transistor applications. The intended abruptness of acceptor profiles is deteriorated by diffusion of manganese in the Ga0.47In0.53As material. The degraded device characteristics obtained are attributed to the acceptor diffusion behaviour established.  相似文献   

15.
An n-type semiconducting diamond film has been synthesized by the hot filament CVD method using diphosphorus pentaoxide as the doping source. The obtained film was identified as polycrystalline diamond containing few sp2 components by means of several methods including Raman spectroscopy. From measurements of the Hall effect and the Seebeck effect, the film was found to be an n-type semiconductor.Patent pending No. Heisei 1-302209  相似文献   

16.
The hole schubweg (distance travelled between deep trapping events) in Teflon FEP (fluorinated ethylene propylene copolymer) is determined by measuring the mean depth of charge injected from the polymer surface, with various fields applied to the sample. It is found that the mean-depth of the injected charge after deep trapping is independent of the electrical field strength from 0.04 to 0.4 MV/cm. The lower value of 0.04 MV/cm is determined by the sensitivity of the method.  相似文献   

17.
A series of experimental studies has been made on the relationship between optical and structural properties of hydrogenated amorphous silicon (a-Si:H) prepared under various conditions. It has been clarified by analysing the results that the shape of the energy spectrum near the band edge and the distribution of the valence-band tail states depend primarily on the structural disorder of the Si network in a-Si:H. On the other hand, the total content and the bonding mode of bonded hydrogen have little effects on these electronic properties of a-Si:H. It has also been found that the distribution of the valenceband tail states might be related to other unidentified factor(s) besides the structural disorder. The present results have been compared with those of the previous experimental and theoretical studies.  相似文献   

18.
An investigation of the growth of heteroepitaxial InAs by MBE is reported. The surface morphology and electrical properties are shown to be critically dependent on growth parameters and the conditions necessary to obtain good material quality are deduced. Analysis of the thickness dependence of the electrical properties of undoped, and Si- or Te-doped InAs shows that interfacial effects contribute to the measured properties. Material remote from the interfacial region compares favourably with VPE- and bulkgrown InAs.  相似文献   

19.
The ohmic contact characteristics of Au/Pt/Ti on degenerated doped n-GaAs were evaluated. Structural and electrical properties were studied by means of X-ray diffraction (XRD), Auger Energy Spectrum (AES) and a HP4145B parameter analyzer. The structural analysis revealed a TiAs phase in the interface between metal multilayer and GaAs at higher annealing temperatures. Electrical measurement showed a minimum ohmic contact resistance of 3×10-4 Ω cm2. The dominant current mechanism was found to be thermionic emission with a barrier height of Φb, of 0.09 V by comparing the experimental data with different theoretical models. Received: 14 December 2001 / Accepted: 4 April 2002 / Published online: 22 November 2002 RID="*" ID="*"Corresponding author. Fax: +86-21/6226-4397, E-mail: zhoujian999@163.net  相似文献   

20.
ZnO and ZnO-Al2O3 thin films were prepared by dc magnetron sputtering and their structural, optical and electrical properties were studied comparatively. It is discovered that the ZnO-Al2O3 thin films remain transparent in a shorter wavelength range than the ZnO films, resulting from the increase of their band gap. Their resistivity decreases by seven orders of magnitude, which is caused by doping of Al to ZnO grains in the film. Preferential orientation of ZnO grains in the ZnO-Al2O3 thin films deteriorates because of the existence of Al2O3 impurity phase in the film. Received: 5 January 1999 / Accepted: 11 October 1999 / Published online: 8 March 2000  相似文献   

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