摘要:

Epitaxial SrTiO3thin films were prepared using low pressure metalorganic chemical vapor deposition. The volatile metalorganic precursors employed were Sr(hexafluoroacetyl acetonate)2⋅tetraglyme and titanium tetraisopropoxide. Single‐phase, epitaxial films were deposited on (100)LaAlO3at a temperature of 810 °C. In‐plane epitaxy was verified using x‐ray phi scan analysis. The SrTiO3films exhibit a significant tetragonal distortion with c/a=1.010(±1.6×10−4) at room temperature. No evidence of fluorine contamination is noted by x‐ray diffraction or by Auger electron spectroscopy measurements. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.113736

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Luminescence spectroscopy measurements of ZnSe/GaAs(100) heterojunctions grown by molecular beam epitaxy reveal the formation of deep levels near ‘‘buried’’ interfaces upon thermal annealing. A pronounced emission at 1.9–2.0 eV appears at temperatures in the 300–400 °C range depending on the ZnSe growth conditions with a constant activation energy of 1.10 eV. X‐ray photoemission spectroscopy indicates a correlation between this deep level and atomic diffusion of Ga and Zn across the heterointerface. Zn‐rich ZnSe growth conditions dramatically reduce this emission, highlighting the importance of local interface composition on thermal stability. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113737

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Nonstoichiometric GaAs obtained by implantation with 2 MeV arsenic ions at 1015cm−2dose is studied. As‐implanted samples show a <200 fs lifetime of photocarriers and low resistivity due to hopping, with mobility less than 1 cm2/V s. Annealing of the samples at 600 °C leads to substantial recovery of postimplant damage, as seen from Rutherford backscattering channeling spectra and mobility increase to about 2000 cm2/V s, but photocarrier lifetime is still about 1 ps. These parameters are similar to those of low‐temperature GaAs annealed at 600 °C, and make arsenic implanted GaAs an interesting material for optoelectronic applications. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113738

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An observation of quantum interference effect in photocurrent spectra of a weakly coupled bound‐to‐continuum multiple quantum well photodetector is reported. This effect persists even at high biases where the Kronig–Penney minibands of periodic superlattice potential in the continuum are destroyed. Our results show that electrons remain coherent over a distance of 40–50 nm. The observation was used to investigate electric field domain formation induced by sequential resonant tunneling in the superlattice. A large off‐resonant energy level alignment between two neighboring wells in the high field domain was observed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113739

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A contact metallization scheme of Ge/Pd(Zn), based on the solid‐phase regrowth principle, has been developed for the formation of Ohmic contact onp‐InP. Typical contact resistivities of low 10−4to low 10−5&OHgr; cm2can be obtained after annealing at temperatures higher than 400 °C. Cross‐sectional transmission electron microscopy study confirmed the solid‐phase regrowth process in the InP substrate. Precipitates of trapped materials during solid phase regrowth have also been observed. A solid phase regrowth model is proposed to rationalize the electrical and metallurgical properties. This solid phase regrowth process is expected to form low resistance Ohmic contact on other In‐based compound semiconductors. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113740

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A direct pump and probe lifetime determination in the ps regime has been made in quantum wells of Si/Si1−xGex. We have used an rf linac‐pumped free‐electron laser to determine the relaxation time associated with intersubband absorption in Si/SiGe quantum wells with a subband separation smaller than the optical phonon energy. This measurement yields a lifetime ofT1=30 ps. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113741

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Radiative recombination of the excitonic states in semiconductor superlattices with an applied electric field is studied theoretically. It is shown that when the electron‐hole Coulomb interaction energy exceeds the miniband width, a coherent excitonic state is created whose oscillator strength surpasses the oscillator strength of a single quantum well by orders of magnitude. It is also demonstrated that a small external field can split the coherent state into isolated well states and thus severely deplete the oscillator strength of the exciton. This opens the possibility of modulating and switching of superradiance in semiconductor devices. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113742

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Current driven instabilities in the collector of III–V heterojunction bipolar transistors (HBT) are investigated. Numerical simulations indicate that in a modified AlGaAs/GaAs HBT the collector current shows oscillatory behavior due to the transferred‐electron (Gunn–Hilsum) effect. Influence of the Kirk effect as well as conditions for oscillation are discussed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113743

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The fluorinated gate oxides grown by the method of liquid phase deposition (LPD) following rapid thermal oxidation (RTO) were studied in this work. Samples with and without aluminum are both investigated in the LPD process. It was found that the amount of F atoms decreases as the LPD oxide was treated subsequently by RTO treatment. For a given time of RTO, the longer the LPD time, the larger the amount of F contained in the gate oxides. But for a given time of LPD, the longer the RTO time, the smaller the amount of F contained in the gate oxides. It was found that the radiation induced oxide charge number density shift &Dgr;Notand the midgap interface trap density shift &Dgr;Ditm, and the oxide breakdown fieldEoxexhibit turnaround dependencies on the LPD growth time. In other words, they are dependent on the amount of F atoms incorporated into the gate oxide. Interestingly, it was found that for the gate oxides grown by the LPD process containing Al have better quality than the LPD without containing Al from the viewpoint of radiation hardness and electric breakdown field. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113744

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report on thedirectobservation of a single‐flux‐quantum (SFQ) pulse. The response of a metal–semiconductor–metal photodiode to a femtosecond laser pulse was used to switch Josephson junctions and to generate an SFQ voltage pulse on a superconducting microstrip line. The detailed shape of the pulse was measured optoelectronically, using a cryogenic electro‐optic sampling system. The measured SFQ pulse had a width of 3.2 ps, an amplitude of 0.67 mV, and a total pulse content of 2.1±0.2 mV×ps, corresponding to the quantum of magnetic fluxh/2e. With larger excitation, multiple SFQ pulses were observed. Numerical simulations are shown to be qualitatively similar to our experimental results. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113745

出版商:AIP    

年代:1995

数据来源: AIP