摘要:

We demonstrate that an amorphous As layer deposited as protection on a GaAs(001) surface grown by molecular beam epitaxy can be removed via reductive etching in an electrolytical cell at sufficiently negative electrode potentials. Employing a specially constructed electrochemical cell filled withH2SO4,we monitored the stripping process of the 50 nm As cap over a period of hoursin situwith x-ray diffraction. Our results suggest that, using this potential controlled stripping, smooth and well ordered GaAs(001) surfaces can be obtained in an aqueous electrolyte. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120239

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We investigated the magnetooptical properties of 0.9 eV luminescence in AlN. The zero-phonon lines at 0.943 eV in AlN are attributed to a transition within ad2configuration because of a characteristic threefold ground-state splitting in magnetic fields. We determine agvalue of1.96±0.07and a zero-field splitting of120±30 &mgr;eVfor the3A2(F)ground state. On the basis of the temperature dependence in a magnetic field, we attribute the 0.943 eV zero-phonon line in AlN to the1E(D)–3A2(F)transition of isolatedV3+.The different fine structures of the excited state in AlN and GaN are explained in a Tanabe–Sugano diagram. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120240

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Planarp-ndiodes with edge termination were fabricated by aluminum implantation onn-type4Hsilicon carbide. These diodes exhibited an excellent blocking behavior up to 1400 V reverse voltage with stable avalanche breakdown at an electric field strength of 2.8 MV/cm. In addition, a nearly classical forward characteristic was observed with both recombination and diffusion current mechanism represented by ideality factors of 1.05 and 1.93, respectively. The turn-on voltage was 2.8 V. At a forward voltage drop of 6.2 V a current density of4000 A/cm2and a differential on resistance below1 m&OHgr; cm2were achieved. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120241

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An atomic-scale model for the kinetics of intermixing of GaAs/AlGaAs, quantum confined heterostructures is presented. It quantifies the effects of the statistical nature of defect diffusion through heterostructures on the Ga/Al interdiffusion across such an interface. The model has been validated by successfully predicting the observed amounts of quantum well intermixing induced by a hydrogen plasma induced defect layer intermixing process. Agreement within 30&percent; of the measurements was obtained for values of the surface releasevelocity>1 &mgr;m s1.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120242

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The photoreflection method is applied to detailed characterization of the ion implanted silicon carbide. Experimentally and theoretically, it is shown that the photoreflection method can be an effective tool for the determination of the dose of implantation and the depth of the implanted layer. It is demonstrated that the photoreflection method also has a high sensitivity to the measurement of optical parameters of the implanted layer. Experimental results are presented for the case of Lely grown 6H–SiC crystals implanted by 37 keVHe+ions. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120243

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Microstructure of GaN films grown by metalorganic chemical-vapor-deposition (MOCVD) onc-sapphire substrates has been accessed as a function of post-growth rapid thermal annealing (RTA) temperatures from 600 °C to 800 °C. The influence of the thermally modified, near-surface crystalline quality on sputtered WSi contact to GaN was also evaluated. Similar planar defects were observed in all heat treated samples; only their density differed. Our analyses demonstrated a strong relationship between the improved GaN crystal quality and postgrowth high-temperature thermal processing. The density of the near-surface defects was lowered by 61&percent; as the annealing temperature was raised from 600 °C to 800 °C. Depression of the near-surface defects encouraged development of the &bgr;-W2Ninterfacial phase and promoted metal-semiconductor interface smoothness. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120244

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Hydrogenated amorphous silicon films were deposited on the unstrained and strained Si substrates by an electron cyclotron resonance plasma source. The photoluminescence spectra show that emission energies are different from each other. The redshift of photoluminescence induced by the biaxial tensile stress is increased with decreasing the temperature in the range of 0.11–0.17 eV. The stress effect also enhances the quantum efficiency significantly. The pseudomorphic growth of Si on a relaxedSi0.75Ge0.25(100) surface provides the strain energy of about 0.17 eV. These comparable results indicate that the shift of emission energy is attributed to the stress effect perturbing the polysilane structure. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120245

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The properties of planar high-temperature superconducting Josephson junctions are not entirely consistent with lowTcmodels. Some of these disparities may be intrinsic, related to the unusual superconducting properties of the electrodes, while others are due to the nonstandard planar geometry. By comparing experimental measurements of a 24° bicrystal substrate Josephson junction with a simple model of nonuniform current flow in a planar geometry, we show that several unusual properties can be explained as extrinsic. We show that nonuniform current feed in a planar geometry leads to a reduced critical current, an unchanged Meissner fieldHco,and a power-law dependence of the critical current onHcodifferent from that expected in an overlap geometry. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120246

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Electrically conductingLaNiO3(LNO) thin layers were deposited on(100)SrTiO3(STO) and(100)LaAlO3(LAO) substrates and crystallized at temperatures between 700 and 800 °C. The chemical method of deposition was solution sol-gel processing. X-ray 2&thgr; and rocking curve measurements, &fgr; scans, and atomic force microscopy studies revealed the degree of crystallinity and heteroepitaxy for the integrated electrodes. The full-width at half-maximum for (100) LNO deposited on LAO and STO was 0.16° and 0.25°, respectively. Surface bonding states and chemistry were examined by x-ray photoelectron spectroscopy. The room temperature resistivity of LNO electrodes deposited on STO and LAO was 460 and 340 &mgr;&OHgr; cm, respectively. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120247

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Transparent nanocrystalline diamond ceramics, consisting of a few nanometer-sized diamond crystallites that are unstable in themselves because of higher surface energy, were fabricated successfully fromC60fullerene using a shock compression and rapid quenching technique. The platelets were transparent and very hard, nearly comparable to type IIa diamond. Transmission electron microscopy and electron energy loss spectroscopy revealed that individual crystallites had combined directly or through a very thin and modifiedsp3carbon layer, which possibly stabilized the nanometer-sized crystallites. The size order andsp3configuration of the nanotexture caused the transparency and hardness of the present material. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120248

出版商:AIP    

年代:1997

数据来源: AIP