摘要:

We report a study of the luminescence properties of coherently strainedGaAs1−xNxgrown on GaAs by metalorganic molecular beam epitaxy. Well-defined photoluminescence was observed in samples with a nitrogen concentration up to 3&percent;. Samples subjected to thermal anneals, investigated by x-ray diffraction and photoluminescence, show increased nitrogen incorporation and significant improvements in the luminescence efficiency. A band-gap reduction of more than 400 meV, compared to GaAs, is observed for a nitrogen concentration of∼3&percent;.For the range of nitrogen concentrations investigated here, the band gap follows predictions of the dielectric model of Van Vechten [J. A. Van Vechten and T. K. Bergstresser, Phys. Rev. B1, 3351 (1970), and references therein]. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121206

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Ge1−xCx/Si heterostructure photodiodes with nominal carbon percentages(0⩽x⩽0.02),which exceed the solubility limit, were grown by solid source molecular beam epitaxy onn-type (100) Si substrates. Thep-Ge1−xCx/n-Siphotodiodes were fabricated and tested. Thep-Ge1−xCx/n-Sijunction exhibits diode rectification with a reverse saturation current of about 10 pA/&mgr;m2at −1 V and high reverse breakdown voltage, up to −80 V. A significant reduction in diode reverse leakage current was observed by adding C to Ge, but these effects saturated with more C. Photoresponsivity was observed from these Si-basedp-Ge1−xCx/n-Siphotodiodes at a wavelength of ⩾1.3 &mgr;m, compatible with fiber optic wavelengths. External quantum efficiency of these thin surface-normal photodetectors was measured up to 2.2&percent;, which decreased as the carbon percentage was increased. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121207

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We present device model calculations of the current–voltage(I–V)characteristics of organic diodes and compare them with measurements of structures fabricated using MEH-PPV. The structures are designed so that all of the current is injected from one contact. TheI–Vcharacteristics are considered as a function of the Schottky energy barrier to charge injection from the contact. Experimentally, the Schottky barrier is varied from essentially zero to more than 1 eV by using different metal contacts. A consistent description of the deviceI–Vcharacteristics is obtained as the Schottky barrier is varied from small values, less than about 0.4 eV, where the current flow is space-charge limited to larger values where it is contact limited. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121208

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A variable-temperature reflectance difference spectroscopy study of GaAs grown by molecular beam epitaxy at low-temperature GaAs (LT-GaAs) shows that the Fermi level is mostly determined by the point defects in samples annealed at below 600 °C and can be shifted by photoquenching the defects. The Fermi level is otherwise almost temperature independent, leading to an estimated width of the defect band of 150 meV in the as-grown sample. For LT-GaAs annealed at 850 °C, the Fermi level is firmly pinned, most likely by the As precipitates. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121209

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Copper phtalocyanine (CuPc) films with the thickness controlled in molecular scales have been grown epitaxially on (0001) surfaces of layered materials, and electronic interaction at the interfaces have been studied by photoelectron spectroscopy. Materials with different electronic properties having different work functions(Evac)were chosen as the substrates; semiconductingMoTe2(Evac=4.0 eV),semi-metallic highly oriented pyrolytic graphite(Evac=4.5 eV)and metallicTaSe2(Evac=5.5 eV).Formation of interface dipole layers was found atCuPc/TaSe2interfaces and molecular orbitals involved were identified. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121210

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A passivation scheme involving plasma silicon nitride (PECVD SiN) deposition on top ofSiO2grown by rapid thermal oxidation is developed to attain a low surface recombination velocity (S) of nearly 10 cm/s on the 1.25 &OHgr; cmp-type (100) silicon surface. Such lowSvalues are achieved by the stack structure even when the rapid thermal oxide (RTO) or PECVD SiN filmsindividuallyyield poorer surface passivation. Critical to achieving lowSby the RTO/PECVD SiN stack is the use of a short, moderate temperature anneal (in this study 730 °C for 30 seconds) after the stack formation. This thermal treatment is believed to enhance the release and delivery of atomic hydrogen from the SiN film to theSi–SiO2interface, thereby reducing the density of interface traps at the silicon surface. Compatibility with this post-deposition anneal makes the stack passivation scheme attractive for cost-effective solar cell production where a similar anneal is required to form screen-printed contacts. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121211

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Using previously published relaxation models [D. J. Dunstan, P. Kidd, L. K. Howard and R. H. Dixon, Appl. Phys. Lett.59, 3390 (1991) and D. Gonza´lez, D. Arau´jo, G. Arago´n, and R. Garcı´a, Appl. Phys. Lett.71, 2475 (1997)] that predict the strain relaxation in the InGaAs/GaAs system, before and during the stage of relaxation saturation, the critical thickness where dislocation interactions begin to limit the plastic relaxation is estimated. The approximations used to deduce an analytical expression are shown to be appropriate for describing the regime of relaxation considered. A good agreement with experimental data previously published by other authors permits a physical explanation for the different observed regimes of relaxation to be given. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121212

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The effect of an inclined substrate on heteroepitaxial diamond has been investigated on 4° off &bgr;-SiC(001) tilted around the [1¯10] axis. Homogeneous macro steps with (001) terraces are observed in the [1¯10] direction forming a vicinal angle of 3°–4° from the (001) surface reflecting the substrate inclination. The selective growth is effective even if the dominant orientation is inclined by several degrees from the surface normal. The tilt deviation is less than 1° in the heteroepitaxial film.p-channel field effect transistors have been fabricated on these heteroepitaxial films. The device performance is as good as that on homoepitaxial films. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121213

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Accurate determination of thermal parameters of microbolometer-based sensors is of considerable interest for many applications. The most important parameters are thermal time constant, heat capacitance and thermal conductance. In this work, we have developed a technique to measure all three quantities using a single electrical measurement. The method involves the measurement of time dependent output voltage of a balanced Wheatstone bridge containing a microbolometer under pulse bias condition. The validity of the approach is verified experimentally using metal–film microbolometers. The experimental results are in excellent agreement with the theoretical analysis of the measurement technique.©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121214

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Ultrathin, coherently strained Sn/Si andSnxSi1−x/Sialloy quantum well structures with substitutional Sn incorporation far in excess of the equilibrium solubility limit have been fabricated via substrate temperature and growth flux modulations in molecular beam epitaxy. Sn/Si single and multiple quantum wells with Sn coverage up to 1.3 ML,Sn0.05Si0.95/Simultiple quantum wells of up to 2.0 nm, andSn0.16Si0.84/Simultiple quantum wells of up to 1.1 nm are determined to be pseudomorphic, and coverage-dependent Sn segregation dynamics are observed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121215

出版商:AIP    

年代:1998

数据来源: AIP