摘要:

The first stages of the growth of highly strained ZnTe on (001)CdTe are studied by reflection high energy electron diffraction (RHEED) with real‐time monitoring of the surface in‐plane lattice spacing and of the width of the streaks along the [100], [110], and [11¯0] azimuths. A large, oscillating, elastic relaxation is measured below the critical thickness (≊5 ZnTe monolayers) in the [11¯0] azimuth while a small excess of tensile stress with regard to the CdTe substrate is observed in the [110] azimuth. These effects are attributed to an anisotropic nontetragonal elastic distortion at the free edges of elongated 2D ZnTe‐monolayer islands. For large deposition times (i.e., after the critical thickness), the RHEED observation gives very good information about the nature of the dislocations occurring in the multiplication process. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113386

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We present a back gated 2DEG (two‐dimensional electron gas) structure using low‐temperature grown (LTG) GaAs as a barrier layer between the back gate and the undoped GaAs channel. The sheet concentration of the 2DEG can be linearly varied from full depletion up to 3×1011cm−2at 12 K. When this charge modulation is modeled by a simple parallel plate capacitor, we find that the distance between the plates is approximately equal to the channel thickness rather than the actual spacing between the 2DEG and the back gate (which is the channel thickness plus the LTG GaAs thickness). We explain this behavior by observing that the leakage path is limited by the triangular barrier to conduction formed at the interface between the LTG GaAs defect band and the undoped GaAs channel conduction band. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113387

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report molecular beam epitaxial study of wide band gap (≳2.9 eV at room temperature) MgZnSSe on (001) oriented GaAs using ZnS, Mg, Zn, and Se sources. Although the growth is under group II rich condition, the compositions of S and Mg in the MgyZn1−ySxSe1−xare linear functions of flux ratios,PZnS/PSeandPMg/PZnS, up to 35%, respectively. Mirrorlike surface and low defect density (5×104cm−2) MgZnSSe with band gap close to 3.1 eV can be achieved. Composition modulation, tweedlike contrasts and strain contrasts in the MgZnSSe are observed from transmission electron microscope analysis. For the first time, a miscibility gap at high S and Mg compositions is reported. Nitrogen‐free radicals are used as thep‐type dopant for the doping study. For the MgZnSSe with room‐temperature band gap energy higher than 2.9 eV, the net acceptor concentration decreases as the band gap energy increases. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113388

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

First‐principles calculations have been performed for ordered and disordered zinc‐blende Al0.5In0.5N alloys including full relaxation of bond lengths and bond angles. The disordered alloy is predicted to have a mixing enthalpy of +39 meV/atom and a bowing parameter of +2.53 eV at the &Ggr;‐point transition. The similarity of the bulk zinc‐blende and wurtzite &Ggr;‐point transitions also allows an estimate to be made of the energy gap versus composition for wurtzite alloys. In particular, the wurtzite AlInN alloy lattice matched to GaN is predicted to have an energy gap of 5.0 eV. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113389

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Remarkably low electron density of Si adatoms at the Si(111)‐7×7 phase boundary was found by scanning tunneling microscopy. The observed charge transfer was apparent with sample bias voltages down to ∼−0.8 eV, close to the value of the dangling bond state of the rest atoms in the Si(111) 7×7 surface. In consideration of the DAS (dimer‐adatom‐stacking fault) model, the observed charge transfer could be related to the structural change in the dimer layer caused by phase mismatching at the boundary. In fact, such charge transfer was not observed at the less disordered boundaries formed by introducing 5×5 half unit cells. Similar large charge transfer was found to occur in the quenched disordered 1×1 structure. These results agree with the similar chemical reactivity observed in the two disordered structures. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113766

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The Schottky barrier height was measured for five different materials on undoped In0.52Al0.48As grown by molecular beam epitaxy (MBE). Of the materials tested, two were transparent conductors, indium‐tin‐oxide (ITO), and cadmium tin oxide (CTO) and for comparison, three were opaque metals (Au, Ti, and Pt). The barrier heights were measured usingI–Vmeasurements. Due to the high series resistance created by the undoped In0.52Al0.48As, the Norde method [J. Appl. Phys.50, 5052 (1979)] was used to plot theI–Vcharacteristics and extract the Schottky barrier height. The Schottky barrier heights were determined to be 0.639, 0.637, 0.688, 0.640, and 0.623 eV for ITO, CTO, Au, Ti, and Pt, respectively. Previously published results for Schottky barriers on In0.52Al0.48As are compared with our measurements. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113767

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Time‐resolved photoluminescence spectroscopy has been used to probe the dynamics of optical transitions in GaN epitaxial layers grown by molecular beam epitaxy. In particular, systematic measurements on a band‐edge transition at about 3.42 eV have been carried out. Recombination lifetimes of this transition have been measured at different emission energies. Our results clearly show that the time‐resolved photoluminescence can provide immense value in the understanding of the dynamic processes of optical transitions in GaN. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113768

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The properties of SiO2films deposited in a remote plasma enhanced chemical vapor deposition (RPECVD) process with chlorine addition into the SiH4–N2O reactants has been studied. With Cl2addition, the interface trap density (located at ∼Ev+0.3–0.35 eV) was decreased and strained silicon bonds were relaxed. As chlorine partial pressure and deposition temperature were increased, however, porosity and surface roughness of the film were increased due to the formation and desorption of Si–Cl or O–Cl bonds. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.113769

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Efficient room‐temperature vapor‐phase etching of SiC by the compound dioxygen difluoride (FOOF) has been demonstrated. FOOF was generated using a design based on thermal‐atomization technique which produced gram quantities of the compound per hour. On both poly‐ and epitype silicon carbide at room temperature, about 6% of the FOOF molecules striking the surface reacted to form SiF4and CO. Examination by atomic force microscopy (AFM) showed that the roughness and morphology of the etched surface were virtually indistinguishable from those of the original surface. No residues or anisotropies were present on the etched surface. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113770

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photoluminescence (PL) characteristics of Se‐doped Ga0.5In0.5P/(Al0.5Ga0.5)0.5In0.5P double heterostructure (DH) on GaAs substrates were investigated at room temperature. The PL intensity and the decay time both strongly depend on the cladding‐layer carrier density. Up to a carrier density of 2.5×1017cm−3, the PL intensity increases linearly with carrier density, while the decay time is almost constant. For carrier densities larger than 2.5×1017cm−3, the PL intensity and the decay time decrease linearly and quadratically with carrier density, respectively. We also studied the PL characteristics of Se‐doped Ga0.5In0.5P and (Al0.5Ga0.5)0.5In0.5P single layers on GaAs substrates. We found that the carrier density dependence of DH governed by the cladding layer is similar to that of (Al0.5Ga0.5)0.5In0.5P single layers. These results indicate that a nonradiative interfacial recombination process dictates the DH PL characteristics and that the quality of the cladding layer affects the PL radiative efficiency. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113771

出版商:AIP    

年代:1995

数据来源: AIP