摘要:

AlxGa1−xAs-GaAs-InyGa1−yAsquantum well heterostructure (QWH) lasers withp+-n+ GaAs–InyGa1−yAsreverse-biased tunnel junctions (hole sources) located in the upper cladding of standard lasers and in oxide-defined cavities (requiring lateral bias currents) are demonstrated. The tunnel junctions, introduced to aid lateral current spreading, are grown at different distances from the waveguide active region in a standard QWH structure to determine first the effect of heavily doped tunnel layers on laser threshold currents. Other QWH laser crystals are oxidized to form oxide-aperture devices with, in addition, either a top confining oxide or a top and bottom oxide confining layer. Hole injection is provided between the oxide layers with the aid of the tunnel contact junction and lateral electron current. The buried tunnel contact junction is shown to be an effective method to make possible hole injection via a lateral electron current, with only a modest increase (a small penalty) in voltage drop and series resistance compared to standard devices. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120071

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Cold cathode structures have been fabricated using AlN and graded AlGaN structures (deposited onn-type 6H-SiC) as the thin film emitting layer. The cathodes consist of an aluminum grid layer separated from the nitride layer by aSiO2layer and etched to form arrays of either 1, 3, or 5 &mgr;m holes through which the emitting nitride surface is exposed. After fabrication, a hydrogen plasma exposure was employed to activate the cathodes. Cathode devices with 5 &mgr;m holes displayed emission for up to 30 min before failing. Maximum emission currents ranged from 10–100 nA and required grid voltages ranging from 20–110 V. The grid currents were typically 1 to104times the collector currents. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120052

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Ballistic electron emission spectroscopy (BEES) has been performed on aGaAs/Ga0.8Al0.2As/GaAssingle-barrier structure at 77 and 7 K. The single-interface model widely used for such structures was found to be inadequate in describing the BEES second-derivative spectrum. A more complete model that incorporates electron-wave interference effects is shown to describe the data accurately and consistently over many spatial locations and samples. This model reproduces all measured features in the BEES second-derivative spectrum resulting from electron-wave interference. At 77 K (7 K) the conduction band offset forx=0.2is determined to be 145 meV orQc=0.58(150 meV orQc=0.60) in agreement with accepted values. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120053

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Using current–voltage and ac conductance measurements, nitrogen-doped ZnSe grown by molecular beam epitaxy onp-GaAssubstrates heterostructures was studied. The reverse current–voltage characteristics of the heterojunction show a soft saturation and a hysteresis. A slow current increase takes place following the application of a constant reverse bias until a steady-state value is reached. This behavior is explained in a model involving slow interface states at the heterointerface that result in a voltage-induced barrier lowering. The observation of a broad peak in the ac conductance vs temperature spectra confirms the model. The presence of such states may seriously affect the performance of ZnSe/GaAs-based devices. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120054

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We demonstrate the operation of InSbBi infrared photoconductive detectors grown by low-pressure metalorganic chemical vapor deposition on semi-insulating GaAs substrates. The fabricated photodetector showed a cutoff wavelength of 7.7 &mgr;m at 77 K. The responsivity of the InSbBi photodetector at 7 &mgr;m was about 3.2 V/W at 77 K. The corresponding Johnson-noise limited detectivity was4.7×108 cm Hz1/2/W.The carrier lifetime was estimated to be about 86 ns from the voltage-dependent responsivity measurements. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120429

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The effect of electron beam heating during the preparation of clean silicon surfaces suitable for epitaxial studies in ultrahigh vacuum conditions was investigated using surface chemical characterization techniques and transmission electron microscopy. The electron beam irradiation produced a disordered surface on the incident side of the sample and well-ordered monoatomic steps on the other surface, even at electron energies as low as 3 keV. These results have significant implications for epitaxial thin film growth. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120055

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

GaN epilayers nitridated initially for different times have been investigated by light scattering tomography (LST) and Raman scattering. In the LST images of the plan-view epilayers, the light scattering defects mainly distribute in ⟨112_0⟩ directions. The density of the defects is lower in epilayer nitridated initially for a longer time. The defects are considered to be the straight threading edge dislocations on {11_00} planes. The Raman shift ofE2mode is larger in the sample initially nitridated for a longer time. Our results show that the misfit between the GaN epilayer and theAl2O3substrate is more unfavorably accommodated by the threading edge dislocations in the epilayers initially nitridated for a longer time. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120056

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The interaction of hdyrogenated Si(001) surfaces is studied by means of molecular dynamics using an empirical potential. Above a certain critical external force covalent bonds may be formed between the surfaces even at room temperature, leaving a hydrogenated interface. The critical force is related to the assumptions of the molecular dynamics, thus scaling with the potential, heat transfer, boundary conditions, and the weak long-range interaction omitted. Below this critical force, the hydrogen–hydrogen interactions prevent covalent bonding. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120057

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The electrical properties and the structure of the buried oxide in low dose SIMOX wafers were investigated after 1200 °C oxidation in different diluted oxygen ambients. The thickness of the silicon dioxide grown on top of the thin silicon films was the same for all samples. Correlating the breakdown field and the surface structure of the buried oxide with process conditions showed that the oxidation time was the key parameter for improving oxide performance while the oxygen partial pressure only played a minor role. We suggest that saturation of atomic oxygen in the thin silicon film during oxidation is responsible for this behavior. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120058

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The 180 keVCa+andAr+ions were homogeneously implanted in GaN at temperature of liquid nitrogen. High resolution x-ray diffraction was used to monitor the change of GaN (0002) peak with the dose ranging from5×1012to1×1016 cm−2. It has been found that with increasing dose a new peak beside the GaN (0002) peak appears, grows up, and gradually shrinks until disappearance with arising of the amorphous peak, accompanied with a shift towards smaller angles. The difference betweenCa+andAr+implantation is discussed. Expansion of GaN crystal lattice due toCa+andAr+implantation accounts for this phenomenon and is confirmed by TEM results. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120059

出版商:AIP    

年代:1997

数据来源: AIP