摘要:

Using THz time-domain spectroscopy to measure the complex conductivity of doped silicon from low frequencies to frequencies higher than the THz plasma frequency and the carrier damping rate, we were able to show in the limit of extremely low carrier densitiesN<1013/cm3,that the Cole–Davidson(C–D)type complex conductivity accurately describes the conductivity of doped silicon. In the low N limit theC–Dparameter &bgr; converges to 0.83 forn-type and 0.70 forp-type silicon. In addition, we have observed a new absorption line at 1.9 THz from an unidentified defect insomeof our Czochralski, single-crystal, low-N silicon samples. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121271

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Compositionally graded, strain relaxedSi0.72Ge0.28buffers were grown on vicinalSi(001)substrates by gas source molecular beam epitaxy. Misfit dislocations are shown to run along intersections of the {111} glide planes with the(11n)interface. X-ray diffraction studies demonstrate a relative tilt of the epilayer to the substrate in a direction which depends on the interplay between substrate orientation related preferential dislocation nucleation rates and surface contamination induced heterogeneous nucleation. Atomic force microscopy (AFM) images reveal an anisotropy in surface roughness on the &mgr;m scale related to reduced growth rates on vicinal surfaces. Transport properties at 0.4 K in two dimensional electron gases grown on these relaxed SiGe buffers show anisotropic scattering times similar to interface roughness scattering which can be correlated to terrace configurations in the nm range determined by AFM. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121272

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The three-dimensional (3D) island structure was prepared by molecular beam epitaxy for the lattice mismatchedInAs/GaAs(001)system and its images showing atomic structure on faceted planes were takenin situby ultrahigh vacuum scanning tunneling microscopy (STM). The (113), (114), and (215) faceted planes are observed for the 3D islands. Based on the STM images, atomic structural models are proposed for the faceted surfaces. The surface structure of the (113) faceted planes we propose is different from those observed on the flatGaAs(113)surface. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121273

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Using e-beam lithography and conventional double-angle evaporation, we have fabricatedAl–Al2O3–Alsingle-electron transistors and studied their behavior from 85 mK to about 5 K. The total island capacitanceC&Sgr;of the devices ranges from 120 to 200 aF, with typical estimated junction overlaps of about30 nm×30 nm.At 4.2 K, our devices display well-behaved periodicI–Vgcharacteristics with the maximum charge-transfer function∂I/∂Q0ranging from 4 to 130 pA/e. The electrical characteristics of these devices agree well with the predictions of the Orthodox Theory, with current modulation being observed up to a temperatureT≃e2/(2C&Sgr;kB).Below 1 K small deviations occur, which are partly due to island self-heating effects. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121334

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Electron-spin resonance (ESR) experiments show that the interface degradation induced in thermal (111)Si/SiO2by postoxidation annealing (POA) in vacuum—previously isolated by ESR as a permanent creation ofPb(&convolu;Si≡Si3)interface defects—is strongly enhanced(∼6 times)when performed inH2ambient. It, thus, appears that theH2POA step, standardly applied to passivate interface states (preexistingPbs) naturally introduced during oxidation, effectively creates additional defect entities; the process initiates from∼550 °Conward vis-a`-vis∼640 °Cfor vacuum. The results unveil the atomic nature of one of the mechanisms of the electrically long-known H-induced POA generation of adverse interface states. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121335

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We present results of pressure-dependent photoluminescence (PL) studies of single-crystalAlxGa1−xNepitaxial films grown on sapphire substrates by metalorganic chemical vapor deposition. PL measurements were performed under hydrostatic pressure using the diamond-anvil-cell technique. PL spectra taken from theAlxGa1−xNepitaxial films are dominated by strong near-band-edge luminescence emissions. The emission lines were found to shift linearly towards higher energy with increasing pressure. By examining the pressure dependence of the spectral features, the pressure coefficients for the PL emissions associated with the direct &Ggr; band gap ofAlxGa1−xNwere determined. Our results yield a pressure coefficient of4.0×10−3 eV/kbarforAl0.05Ga0.95Nand3.6×10−3 eV/kbarforAl0.35Ga0.65N.©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121277

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Deep centers in Si-dopedn-GaNlayers grown by reactive molecular beam epitaxy have been studied by deep-level transient spectroscopy as a function of growth conditions. Si-doped GaN samples grown on a Si-dopedn+-GaNcontact layer at 800 °C show a dominant trapC1with activation energyET=0.44 eVand capture cross-section&sgr;T=1.3×10−15 cm−2,while samples grown at 750 °C on an undoped semi-insulating GaN buffer show prominent trapsD1andE1,withET=0.20 eVand&sgr;T=8.4×10−17 cm2,andET=0.21 eVand&sgr;T=1.6×10−14 cm2,respectively. TrapE1is believed to be related to a N-vacancy defect, since the Arrhenius signature forE1is very similar to the previously reported trapE,which is produced by 1-MeV electron irradiation in GaN materials grown by both metalorganic chemical-vapor deposition and hydride vapor-phase epitaxy. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121274

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

There exists a strong correlation between the nitrogen concentration profile and infrared (IR) spectroscopy in gate oxynitrides for metal–oxide–Si (MOS) devices. The hot-electron hardness of the MOS device depends strongly on the nitrogen concentration profile in the gate oxide. It is experimentally found that the concentration ratios of nitrogen atSiO2/Sito the maximum amount of nitrogen in the oxide bulk([N]int./[N]max. bulk)are proportional to the values of IR peak positions of Si–O stretching bonds. A larger value of[N]int./[N]max. bulkindicates a better hot-electron hardness of the MOS device, which can be explained by a reduction ofSiO2/Siinterfacial strain. The hot-electron hardness in the MOS device can be easily assessed by the IR signals of gate oxynitrides. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121336

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Interface trap density distributions within Si for metal–bismuth titanate–silicon capacitors fabricated by chemical solution deposition were investigated. The interface trap density was measured by a conductance technique at room temperature and a value in the order of1011–1012 eV−1 cm−2was found depending on the ferroelectric crystallization temperature. An increase in the annealing temperature results in an increase in the interface trap density. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121337

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Metal–oxide–semiconductor (MOS) capacitors were fabricated onin situdopedn- andp-typeSi1−yCy/Siheterostructures grown on Si substrates by chemical vapor deposition. StrainedSi1−yCyepitaxial layers with substitutional carbon contents up to 1.6&percent; were studied. High frequency and quasistatic capacitance–voltage(C–V)measurements exhibit well-behaved MOS characteristics, indicating high electronic material quality. Band alignments were extracted from MOSC–Vmeasurements and one-dimensional device simulations performed over a range of temperatures. The conduction band energy of strainedSi1−yCyis lower than that of Si by approximately 65 meV for 1 at. &percent; carbon, while the valence band shows negligible offset to Si valence band. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121338

出版商:AIP    

年代:1998

数据来源: AIP