摘要:

We report the observation of Shubnikov–de Haas oscillations in superlattices of GaInAs and InP, showing evidence of two‐dimensional behavior. The electrong‐factor is deduced from both the criteria for resolution of a spin splitting by comparison with the broadening parameter &Ggr;, and from the tilted field method, and is shown to increase with increasing resolution of the Landau levels in a manner consistent with the theory of Ando and Uemura. In the ultraquantum limit, structure at &ngr;=1/2 and &ngr;=1/3 is observed.

ISSN:0003-6951    

DOI:10.1063/1.94290

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Infrared absorption bands for15N in crystalline silicon have been observed for the first time. Isotopic substitution experiments were performed by N+ion implantation into crystalline silicon to confirm the role of nitrogen in absorption bands at 764 and 962 cm−1for14N and at 748 and 937 cm−1for15N. Laser annealing increases the intensity of the higher frequency band. The 962‐cm−1band frequency is close to Si‐N stretch frequencies for planar bonded N in crystalline Si3N4. It is suggested that the lower frequency band is associated with a mode that is made IR active by local distortion, consistent with a distorted substitutional N center identified by Brower in electron paramagnetic resonance studies on laser‐annealed nitrogen‐implanted Si.

ISSN:0003-6951    

DOI:10.1063/1.94291

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The proposition that nanosecond pulsed laser annealing of implanted silicon is accomplished by electron plasma interactions (below 1700 K) has been tested by comparing the threshold energy densities required for epitaxial regrowth, using intense pulsed beams of B+and Ba+ions. Thresholds for 250‐ns pulsed B+(210 keV) (90% electronic energy deposition in Si) and Ba+(285 keV) (44% electronic, 56% collisional) are identical, indicating that the mode of initial energy coupling to the solid is not important. The results agree with quantitative predictions for a normal thermal melting process.

ISSN:0003-6951    

DOI:10.1063/1.94292

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Intracenter transitions in the major deep level EL2 in GaAs were identified for the first time by superimposing photocurrent measurements on those of optical absorption. These transitions were found to be responsible for the characteristic EL2 absorption band between 1.0 and 1.3 eV. At low temperatures (<60 K) intracenter absorption exhibits a fine structure involving the zero phonon line and replicas at energies close to those of transverse acoustic phonons (TA). This coupling with TA phonons is a strong indication that EL2 is an extrinsic self‐trapping center.

ISSN:0003-6951    

DOI:10.1063/1.94293

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We have determined the isoconcentration contours of the deep level EL2 across 3‐in.‐diam, semi‐insulating GaAs crystals grown by the liquid encapsulated Czochralski technique. The contours are essentially fourfold symmetric at the seed end of the crystals. The symmetrical pattern is independent of the melt stoichiometry and the relative direction of crystal and crucible rotation. EL2 distributions in the tail of the same crystals are often of lower symmetry. The results support a native defect model for EL2 in which the formation of the defect is enhanced by stress in the crystal.

ISSN:0003-6951    

DOI:10.1063/1.94294

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We demonstrate a Ga0.47In0.53As/Al0.48In0.52As modulation‐doped photoconductive detector. The detector has a built‐in electric field to separate photogenerated electron‐hole pairs. This allows the electron lifetime to be precisely determined by electrode spacings. When tested by a 200‐ps, &lgr;=1.3  &mgr;m laser pulse, the detector shows an internal gain of 18, a peak external quantum efficiency of 300%, a rise time of 80 ps, a full width at half‐maximum of 250 ps, and an internal gain‐bandwidth product of 72 GHz. Typical devices have 4‐&mgr;m spacings between electrodes and 94‐&mgr;m widths. The detector has a spectral response between 0.6 and 1.65  &mgr;m with a dip at 0.86  &mgr;m. We also measured the noise power of the detector at room temperature. With its capability to be integrated with a modulation‐doped field‐effect transistor, this detector can be useful in a monolithic integrated photoreceiver.

ISSN:0003-6951    

DOI:10.1063/1.94295

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Specimens of Nb3Sn tape have been irradiated at ∼380 K with reactor‐spectrum neutrons to fluences of 1.3×1019n/cm2(E>1 MeV) and the internal friction and dynamic Young’s modulus measured from 6 to 300 K. The softening of the lattice with decreasing temperature is seen to decrease from 40% of the room‐temperature value at 10 K for unirradiated Nb3Sn to 94% at a fluence of 1.3×1019n/cm2. The internal friction &dgr; due to tetragonal domain‐wall motion of the transformed material decreased with increasing fluence, being completely suppressed after ∼4×1018n/cm2. The transformation temperatureTmdecreased from ∼49 K for the virgin specimen to 22 K for a fluence of 3.8×1018n/cm2with no evidence of any tetragonal transformation at all for higher fluences. The lattice‐dynamical and electronic changes responsible for these effects are not known at this time, but are seen to be correlated with the neutron‐induced disorder.

ISSN:0003-6951    

DOI:10.1063/1.94296

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The BaPb0.7Bi0.3O3sputtered film possesses tunnel Josephson junctions at boundary layers [boundary Josephson junction (BJJ)] normal to the film plane in a homogeneous junction array. The film has high efficiency for optical irradiation of the junctions because of the high optical transparency. The letter presents the optical effect on the current‐voltage characteristics for this Josephson junction array locked to a microwave field. The microwave‐induced hysteresis loop caused by voltage locking among junctions in a microwave field is highly sensitive to optical illumination with as low an incident power as a few nanowatts. This probably can be exploited in a future, highly sensitive photodetector.

ISSN:0003-6951    

DOI:10.1063/1.94297

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A shift in the frequency spectrum of a structure induced by a local temperature rise is measured. This technique of detecting shifts in the frequency spectrum of a structure may be used to detect slight temperature‐induced changes in stress distribution, which are in turn caused by local perturbation in the temperature distribution in the structure. Results from a small superconducting coil are presented.

ISSN:0003-6951    

DOI:10.1063/1.94298

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Superconducting niobium patterned to form strip transmission lines on sapphire and silicon dielectric substrates has been used to make passive delay lines, capacitively coupled resonators, and linear‐FM chirp filters. Chirp filters with a 37.5‐ns dispersion and 2.3‐GHz bandwidth were implemented by nonuniformly tapping nondispersive delay lines using proximity directional couplers. Pulse compression tests using two complementary filters agree well with theory. The results demonstrate a technology which promises to provide analog signal processing with about an order of magnitude bandwidth increase over surface‐acoustic‐wave and acousto‐optic devices.

ISSN:0003-6951    

DOI:10.1063/1.94299

出版商:AIP    

年代:1983

数据来源: AIP