摘要:

We present cross-sectional scanning tunneling microscopy (STM) images of strain-induced, self-organized InAs quantum dots grown on GaAs. Samples containing 5 and 10 sequentially grown dot layers are investigated, and dots from different layers are seen to align in vertical columns. Our STM images are in general agreement with previous structural imaging, such as cross-sectional transmission electron microscopy, except that dot crowns appear more truncated. Although the size of the dots in most columns is roughly constant, monotonic changes in diameter are observed in some cases. STM analysis also reveals many new atom-resolved details of electronic structure, including dissolution of the InAs wetting layer and the presence of indium between the dot columns, which we attribute to segregation and diffusion of indium out of the wetting layer during overgrowth. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120553

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We describe the surface topography domain in a strained InGaAs/AlGaAs system on the GaAs (311)B substrate during metalorganic-vapor-phase-epitaxial growth. The surface rearrangement resulting in the formation of nanostructures seems to belong to a Turing-type self-organization phenomenon that results from a spontaneous symmetry-breaking instability in nonlinear dynamical systems. The unique surface morphologies on the high Miller index faces suggest a novel fourth growth mode due to Turing-type self-organization. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119735

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The ultrafast relaxation dynamics of hot electrons, initially photoexcited with an excess energy of 300 meV, are monitored in a high-quality ZnSe epilayer grown on a GaAs substrate by exploiting the intrinsic interferrometric asymmetric Fabry–Perot sample structure. The results are consistent with the expected characteristic electronic LO-phonon emission time of 40–50 fs and provide evidence for the influence of the “hot phonon effect”(or “LO-phonon bottleneck”) on the electron cooling dynamics at carrier densities above∼3×1017 cm−3.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119736

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Persistent photoconductivity has been observed inn-type GaN:Si. The effect is seen at room temperature in both nonoptimally grown films as well as in device quality channel layers. The relaxation dynamics are found to agree with a stretched exponential model of recovery. A comparison between different samples, based upon stretched exponential parameters, Hall measurements, and photoluminescence data is made. The data suggest that the cause of persistent photoconductivity is the same among the different samples and that there is a transition in the relaxation dynamics between room temperature and 130 °C. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119924

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We show that thep-type doping ofGa0.5In0.5Pgrown by solid-source molecular beam epitaxy usingCBr4as a carbon source is very strongly dependent upon the phosphorus flux and upon the substrate misorientation from (100). High densities ofA-type steps and low phosphorus flux favor the incorporated carbon acting as ap-type dopant. We demonstrate that with the substrate orientation and phosphorus flux chosen to satisfy these two criteria, doping ofC:Ga0.5In0.5Pinto the mid-1018 holes/cm3range can be achieved for the as-grown material. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119737

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on the spectral and temperature dependence of persistent photoconductivity (PPC) in metal-organic chemical vapor deposition grown unintentionally dopedn-type GaN. The PPC effect is detectable up to temperatures of at least 352 K, the highest temperature used in this study. At 77 K, the conduction persists at a level 80&percent; higher than the equilibrium dark conduction for over104 safter removing the excitation. We have determined the spectral dependence for the optical cross section for PPC and obtain an optical ionization energy of ∼2.7 eV. The temperature dependence of the photoconductivity decay and its nonexponential shape are explained by a distribution of capture barriers with a mean capture barrier of 0.2 eV and a width of ∼26 meV. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119738

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A field-enhanced Si–Si bond-breakage mechanism is presented which accurately describes the time-dependent dielectric breakdown behavior recently reported for thin-filmSiO2dielectrics over a wide range of fields and temperatures. The breakdown kinetics (both the field and temperature dependence) are shown to be consistent with a field-dependent dipolar energy term associated with an oxygen vacancy which serves to reduce the activation energy required for Si–Si bond breakage. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119739

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A lead sulphide/lead titanate/silicon(PbS/PbTiO3/Si)heterostructure was manufactured by successive deposition ofPbTiO3and PbS thin film on a single crystalline,p-type, Si substrate. Chemical methods were used for deposition. A three electrode configuration was used to control the photoconductivity of PbS thin film by field effect, through the ferroelectricPbTiO3thin film. The spectral distribution of the photoconductive signal shows two maxima, situated at 1.1 and 2.45 &mgr;m. It was found that the photoconductive signal at 1 &mgr;m varies of about eight times when the voltage applied on the Si substrate is varied between−1and+1 V.At 2 &mgr;m the photoconductive signal is almost independent of the applied voltage on the Si substrate. The observed results are explained considering a ferroelectric field effect by which the photogenerated carriers in Si influence the photoconductive signal in the PbS thin film. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119740

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Gettering of Fe in silicon-on-insulator material has been investigated on both the bonded and separation by implantation of oxygen (SIMOX) platforms. Reduction of electrically active iron in intentionally contaminated and annealed wafers has been measured by deep level transient spectroscopy. These data, coupled with structural characterization techniques, such as transmission electron microscopy and preferential chemical etching, provide evidence that structural postimplantation damage below the buried oxide (BOX) in SIMOX wafers is an effective site for gettering of iron with the iron gettering efficiency varying with the SIMOX processing. Gettering was not observed in bonded wafers, and the lower BOX interface did not provide any iron gettering in either bonded or SIMOX wafers. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119741

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Pressure-dependent photoluminescence (PL) in several GaInP(ordered)-GaAs quantum well structures grown by metal organic vapor phase epitaxy is reported. Quantum well emission from GaAs is observed only in structures where thin(∼2 nm)GaP layers are inserted between the GaAs well and the GaInP barrier. By extrapolating the energies of the various inter and intralayer PL transitions observed under pressures (up to 5.5 GPa) to zero pressure, the different band offsets of the heterostructure have been determined. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119742

出版商:AIP    

年代:1997

数据来源: AIP