摘要:

The formation of thin AlN films on NiAl(001) has been studied by means of high resolution electron energy loss spectroscopy (HREELS), low‐energy electron diffraction (LEED), and Auger electron spectroscopy. The AlN films were grown by the adsorption of NH3on NiAl(001) atT=80 K and subsequent thermal decomposition at elevated temperatures. After annealing toT=1250 K, a distinct LEED pattern appears which exhibits pseudo‐twelvefold symmetry. This indicates the formation of two hexagonal domains of AlN which are rotated by 90° with respect to each other. HREEL spectra of the ordered AlN film show a Fuchs–Kliewer phonon mode at 865 cm−1in good agreement with theoretical spectra calculated on the base of the dielectric theory. The electronic energy gap of the thin AlN films is determined to beEg&bartil;6.1 eV. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359215

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The multipleDXrelated emission centers are studied using the isothermal time analyzed transient spectroscopy (TATS). Four distinct emitting centers have been obtained using higher order TATS in thesamesilicon doped Al0.33As0.67As sample. A systematic observation of these levels has helped in reducing the ambiguity regarding the emission parameters of theDXcenters. Particularly the activation energies, the nature of nonexponentiality of emission, and the effect of charge redistribution for theDXcenter have been made explicit. Our results suggest that the activation energy of each of the four distinct centers have a Gaussian distribution with similar full width half maxima of about 20 meV. Limitations of temperature scanning techniques such as deep level transient spectroscopy are pointed out. ©1995 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.359216

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report results of electron paramagnetic resonance, photothermal deflection spectroscopy, and capacitance‐voltage measurements on amorphous hydrogenated silicon nitride (a‐SiNx:H) thin films exposed to ultraviolet (UV) illumination. It has been previously shown that exposure to UV light activates silicon dangling‐bond defects, i.e.,K0centers, ina‐SiNx:H thin films. Here, we demonstrate that the initially UV‐activatedK0center can be irreversibly annihilated at long illumination times. Because this effect seems to scale with H content of the measured films, we propose that hydrogen may be passivating theK0defects during the extended UV exposure. We also show that films subjected to long UV exposures trap charge as efficiently as those having much largerK0concentrations. A few possibilities to explain this effect are discussed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359593

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have studied the deep levels in the lattice‐matched InP/(InAlGa)As heterojunction system. Fivep‐njunction samples were grown by metalorganic chemical vapor deposition with varied Al composition of 0%, 16%, 36%, 45%, and 55%. A vacancy‐related deep electron trap was found at the InP/(InAlGa)As interface. This trap has less concentration in the sample with higher Al composition, and is not observed when Al composition is greater than 55%. Its activation energy within the band gap increases with the increasing Al composition. The trap can be eliminated by rapid thermal annealing at 700 °C. Current‐voltage characteristics show that this trap acts as recombination centers under forward bias condition. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359217

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The linear absorption coefficient of InAs/InxGa1−xSb superlattices is optimized with respect to layer widths, indium content, substrate type and substrate orientation, interface type, and choice of buffer layers based on a model envelope‐function approach (EFA) involving the solution of a 6×6 EFA Hamiltonian (heavy, light, and conduction bands) for wave functions and subband energies. Free‐standing superlattices as well as superlattices matched to a number of substrates are considered. In general, increasing the indium mole content from 0 to 0.4 doubles the magnitude of absorption. Changing the substrate orientation from [001] to [111] significantly increases absorption in all cases studied due to the increased heavy‐hole mass and the larger InAs‐conduction‐band–InGaSb‐valence‐band offset in the [111] direction. The use of an In0.4Ga0.6Sb substrate leads to higher absorption because all the beneficial effects of strain are placed in the InAs layer, which is more sensitive to strain than is the InGaSb layer. The larger valence–conduction‐band offset for InSb than for GaAs interfaces also leads to higher absorption. The model results agree best with available data when a 100 meV InAs‐conduction‐band–GaSb‐valence‐band offset is used. Specific superlattice parameters that optimize absorption for free‐standing superlattices on GaSb at three cutoff wavelengths are proposed. ©1995 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.359218

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Strain‐induced effects in quantum wells of InAsxP1−x/InP, InxGa1−xAs/InP, and InxGa1−xAs/ In0.52Al0.48As on (111) InP substrates are investigated. The strain induces a large piezoelectric field in these structures, and causes a large change in their energy band edges. Consequently the band structure of the quantum wells is dramatically modified, and the dependence of interband transition energies on alloy composition is different from that of quantum wells on (100) substrates. Moreover, a larger critical layer thickness is found for the quantum wells studied. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359219

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The interfacial reactions in the structures of Si/SiO2(500 nm)/Ru (65 nm) (up to 950 °C) and Si/SiO2(500 nm)/Ru (72 nm)/Al‐0.8 wt % Si (630 nm) (up to 700 °C), were studied by Rutherford backscattering spectrometry, Auger electron spectroscopy, x‐ray diffractometry, selected‐area electron diffraction, energy‐dispersive x‐ray spectroscopy, scanning electron microscopy, and transmission electron microscopy. A thin film of Ru was stable on a SiO2substrate up to 30 min in a vacuum anneal at 950 °C. In vacuum, a fast interfacial reaction between the Ru thin film and the Al‐Si overlayer started between 550 and 575 °C, resulting in the formation of a Si/SiO2/ RuAl2/(Ru4Al13)Al‐Si layer sequence. Similar to the reactions between Pt group metals and Al, the Ru/Al reaction is nonuniform. It is controlled by a nucleation mechanism and is accompanied by void formation. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359220

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Forward and reverse bias dark current characteristics ofn+pmesa diodes and solar cells fabricated from metalorganic chemical vapor deposition grown Ga0.5In0.5P have been examined, and dark current behavior has been correlated with Ga0.5In0.5P solar cell conversion efficiency. Dependencies of dominant dark currents on voltage, temperature, and doping density were found to be consistent with recombination theory. Recombination dark current with an ideality factor ofA=1.9–2.1 was dominant in the voltage range of ∼0.5 to 1.5 V and ∼0.8 to 1.2 V for devices with ap‐base doping density of ∼1016and 1017cm−3, respectively. Reverse current‐voltage‐temperature measurements identified two dominant deep levels at 0.10 and ∼0.45 eV relative to either the valence‐ or conduction‐band minimum. The carrier recombination was found to occur through these deep level centers in then+pjunction.

ISSN:0021-8979    

DOI:10.1063/1.359221

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Electronic states inn‐type GaAs/AlxGa1−xAs heterojunctions are studied by deep‐level transient spectroscopy in the Al mole fraction range from 0.25 to 1.00. A series of four well‐defined deep levels is characteristic of the inverted GaAs/AlxGa1−xAs interface (GaAs grown on AlxGa1−xAs) grown by conventional molecular‐beam epitaxy under arsenic‐stable conditions without growth interruption. It is shown that the series of four levels originates from intrinsic defects which are associated with arsenic vacancies and antisites. In particular, two charge states of the isolated arsenic vacancyVAscan be identified. Except for the sheet very close to the inverted heterointerface then‐type AlxGa1−xAs layers are found to be almost free of intrinsic deep levels in the entire composition range. For the investigated samples, the compositional dependence of the level energies shows that the arsenic vacancy is predominantly surrounded by Al atoms. From the compositional dependence of the level concentrations it follows that the arsenic vacancies at the interface are formed above a composition threshold of 0.25. The distinct distribution of intrinsic defects at the inverted GaAs/AlxGa1−xAs interface can be explained by a stable defect configuration near the AlxGa1−xAs surface during growth. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359222

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A method for determining surface charge decay [Q(t)], using a coaxial cylindrical capacitor arrangement and an electrometer interfaced to a PC, has been adapted so as to perform relatively straightforward measurement of resistivity in the surface region of insulators. A charge transport model is presented, based on Mott–Gurney diffusion, which allows interpretation of the data especially for the initial phase of surface charge decay. Resistivity measurements are presented for glass, mica, plexiglas, and polyethylene, covering the range 109–1018&OHgr; m, as an illustration of the useful range of the instrument for static and antistatic materials, particularly in film or sheet form. Values of surface charge diffusion constants have also been determined for the materials. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359223

出版商:AIP    

年代:1995

数据来源: AIP