摘要:

Undoped aluminum nitride films were grown on 4H or 6H silicon carbide substrates, using metal–organic chemical-vapor deposition at 1150 °C. Different growth conditions were used, and two different V/III ratios were tested. Metal–insulator–semiconductor capacitors were made for high-frequency capacitance–voltage measurements at room temperature, from which the film thickness was determined. Accumulation, depletion, deep depletion, and inversion were seen for the best films, which also displayed peaks in x-ray diffraction rocking curves. Although large flatband voltage shifts occurred, indicating a fixed charge and interface trap problem, low conductance was observed. A flow of ammonia during ramp-up was found to improve the AlN films. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119229

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A new ripple formation mechanism is observed in excimer-laser irradiated polycrystalline silicon (polysilicon) films on oxidized silicon wafers. The ripples form for polysilicon films capped with a thin oxide, and for laser fluences that completely melt the buried polysilicon. The resulting ripples are unlike those previously reported in that (1) their wavelength cannot be predicted by Rayleigh’s diffraction condition, (2) their wave fronts are arranged in chaotic patterns, rather than parallel lines, and (3) the wave fronts can be manipulated by changing the polysilicon surface topology. The characteristics of these ripples are investigated in the context of understanding the underlying physics. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119230

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A near-field scanning optical microscope (NSOM) is used to study the local photoresponse ofCu(In,Ga)Se2thin film solar cells. The grain boundaries of the small grains(<1 &mgr;m)show some reduction in photoresponse; however the photoresponse is significantly reduced near most crevices separating large grains(>10 &mgr;m).In addition, NSOM images show response variations from grain to grain and areas of reduced photoresponse which have no corresponding topography. Photovoltage imaging of the cleaved side of the solar cells reveals the depth and nonuniformities of the actualp-njunction. It is found that the response of thep-njunction varies on a 0.5 &mgr;m length scale. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119231

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The importance of atomic relaxations, chemical disorder, and epitaxial constraints on the band gap of random, anion-mixed nitride alloys GaPN and GaAsN have been investigated, via pseudopotentials calculation. It has been demonstrated that simple approximations such as the virtual crystal approximation, or the use of high-symmetry ordered structure to mimic a random alloy, or the neglect of atomic displacements, are inadequate. It is found that a fully relaxed, large supercell calculation reproduces well the experimental band gaps of GaPN and GaAsN films. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119232

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

&bgr;-Ga2O3single crystals were grown by the floating zone method and their conductivity along thebaxis was controlled from<10−9to38 &OHgr;−1 cm−1by changing the growth atmosphere. By using feed rods doped with Sn, the grown crystal became highly conductive even under oxidative atmosphere. The optical transmission spectra showed that the&bgr;-Ga2O3single crystal with 0.32 mm was transparent in the visible and ultraviolet region, with 20&percent; transmittance at the fourth-harmonic wave of the Nd:YAG laser (266 nm). The band-gap widening was observed with the increasing of the carrier concentration. It is expected that the light of the KrF laser can be transmitted in the heavily doped&bgr;-Ga2O3.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119233

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on the molecular-beam epitaxy of ZnBeSe ternary alloys lattice matched onto GaAs substrates. We demonstrate that these alloys can be grown with a high structural perfection. X-ray linewidths down to 27 arcsec are obtained even though the growth is carried out on bare substrates. Transmission electron microscopy reveals the high quality of the interface. Photoluminescence spectra of undoped layers are dominated by free-exciton recombinations. The excitonic gap is determined to be 2.863 eV at 9 K. Finally, high carrier concentrations are obtained for bothn-type andp-type doping. These results are promising in view of fabricating laser diodes with this material system. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119234

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Impact ionization coefficients have been deduced from photomultiplication measurements performed onGa0.52In0.48Pp–i–ndiodes with nominal intrinsic region thicknesses of 1 .0, 0.7, and 0.2 &mgr;m. The results indicate that &bgr;, the hole ionization coefficient, is slightly greater than &agr;, the electron ionization coefficient at low fields, and they both become effectively equal at high fields. &agr; and &bgr; are also found to be significantly lower than GaAs across the range of electric fields studied, with correspondingly higher breakdown voltages. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119235

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The short-pulse laser crystallization and interference structuring of amorphous germanium films were investigated by time resolved reflection measurements and Raman spectroscopy. We demonstrate that submicrometer crystalline structures with very sharp lateral interfaces can be produced by laser interference crystallization of nonhydrogenated samples. In hydrogenated films, on the other hand, the film surface disrupts upon laser exposure leading to the formation of a free-standing crystalline membrane. The Raman spectra of laser crystallized germanium display effects of finite crystallite size and stress. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119236

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The effect of laser annealing on important detector characteristics such as dark current, spectral response, and absolute responsivity is investigated for bound-to-continuum GaAs/AlGaAs quantum-well infrared photodetectors (QWIPs) operating in the 8–12 &mgr;m wavelength regime. A set of experiments was conducted on QWIPs fabricated from both as-grown and laser-annealed multiple-quantum-well structures. Compared to the as-grown structure, the peak spectral response of the laser-annealed structure was shifted to longer wavelengths, though absolute responsivity was decreased by about a factor of two. In addition, over a wide range of bias levels, the laser-annealed QWIPs exhibited a slightly lower dark current compared to the as-grown QWIPs. Thus, the postgrowth control of GaAs/AlGaAs quantum-well composition profiles by laser annealing offers unique opportunities to fine tune various aspects of a QWIP’s response. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119237

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The transient ion drift (TID) method was used to measure quenched interstitial copper concentrations in both copper plated and copper implanted silicon. Comparison with existing literature data allows one to conclude that, contrary to the general expectation, it is possible to quench in most of the Cu dissolved at temperatures of 600 °C and below. This result suggests that the TID technique could be an excellent means to detect copper contamination inp-type silicon. The expected detection limit, on the order of1011 cm−3,makes the method a potentially interesting tool to use in gettering or in-diffusion barrier studies. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119238

出版商:AIP    

年代:1997

数据来源: AIP