摘要:

Clean GaP(001)‐(4×2) and H2S‐treated (1×2) surfaces are studied by scanning tunneling microscopy (STM). We have observed a (4×2)/c(8×2) STM image for the cation‐stabilized GaP(001) surface. The result suggests that the unit cell of the (4×2) structure consists of two Ga dimers with two missing Ga dimers. For the (1×2)S surface, the previous model that sulfur atoms are adsorbed on the Ga dimer and that a missing row of sulfur is formed along the [11¯0] direction is supported by the STM result. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114517

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

N‐ andp‐type regions have been produced in GaN using Si+and Mg+/P+implantation, respectively, and subsequent annealing at ∼1100 °C. Carrier activation percentages of 93% for Si and 62% for Mg were obtained for implant doses of 5×1014cm−2of each element. Conversely, highly resistive regions (≳5×109&OHgr;/&laplac;) can be produced in initiallyn‐ orp‐ type GaN by N+implantation and subsequent annealing at ∼750 °C. The activation energy of the deep states controlling the resistivity of these implant‐isolated materials is in the range 0.8–0.9 eV. These process modules are applicable to the fabrication of a variety of different GaN‐based electronic and photonic devices. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114518

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have investigated the photoluminescence emission energy of InP dots as a function of cap layer thickness. We find a strong blue‐shift with increasing cap layer thickness. The strain tensor in the dot as well as in the surrounding matrix has been modeled using finite element methods and the band gap has been calculated using deformation potential theory. We find good agreement between calculation and experiment. For uncapped dots we find that the emission energy is lower than for biaxially strained InP, and is indeed close to unstrained InP. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114519

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Using nanolithographic techniques we deposit an array of ferromagnetic dysprosium dots with perioda=500 nm on top of GaAs–AlGaAs heterojunctions. The spatially periodic stray fields affect drastically the magnetotransport properties of the electrons in the underlying two‐dimensional electron gas and give rise to the long predictedmagneticcommensurability oscillations. We show that such a semiconductor‐ferromagnet hybrid system can be used to study the magnetic properties of nanoscale particles. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114520

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have systematically studied the dependence of the electrical properties of Si‐doped (311)A GaAs on the growth conditions in molecular beam epitaxy and have established a phase diagram for the conduction type as functions of the growth temperature and the V4/III flux ratio. A sharp boundary is observed for the transition between thep‐ andn‐type conduction, on both sides of which the activation efficiency of Si is close to unity. Furthermore, it is found that, in contrast to the case of the (111)A GaAs, the conduction‐type conversion in Si‐doped (311)A GaAs does not show a clear correlation with the macroscopic surface morphology, suggesting that the mechanism for the conduction‐type conversion in Si‐doped (311)A GaAs is different from that for the (111)A orientation. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114521

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We calculate the binding energies of donors bound toXvalleys in type‐II GaAs–AlAs quantum well structures using an anisotropic variational method which enables us to take into account the effective mass anisotropy and quantum confinement. For a comparative study, we use two sets of effective masses obtained from different measurements [B. Rheina¨nderetal. Phys. Status Solidi B49, K167 (1972) and M. Goiranetal., Physica B177, 465 (1992)]. We show that the binding energies have a pronounced dependence with the effective mass, AlAs layer thickness, and impurity position. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114490

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Exciton and biexciton transitions have been observed in low‐temperature (10 K) photoluminescence from CdxZn1−xSe/ZnSe (x=0.2) multiple quantum well samples grown by molecular beam epitaxy. Transient photoluminescence experiments were conducted to study the dynamics of carrier decay associated with these processes. The formation of exciton and biexciton species is confirmed by examining their energy positions, intensity dependence on excitation power density, spectral line shapes, relative decay lifetimes, and polarization dependence. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114491

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The defect structure of Si substrates at their &bgr;‐SiC/Si interfaces generated in a chemical vapor deposition (CVD) process by carbonization with C2H4has been investigated in detail by transmission electron microscopy (TEM) using differently prepared cross section and planar specimens. A new category of defects of minute size and high area density has been found and identified as SiC micropipes formed by Si outdiffusion and simultaneous ingrowth of SiC. A model of self‐adjusting micropipe formation is proposed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114492

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Interface state generation in oxynitride gate dielectric devices with tungsten‐polycide (W‐polycide) and polycrystalline silicon (poly‐Si) gate structures were investigated. A significant amount of fluorine‐induced interface states were detected in W‐polycide gate device with nitridation of thermal gate oxide by both the charge pumping technique and capacitance/gate voltage (C/V) measurement. Re‐oxidation of oxynitride gate oxide results in partial annealing of these interface states. A model of the fluorine induced strain gradient between silicon dioxide and silicon (SiO2/Si) interface was proposed to explain the extra interface state generation mechanism. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114493

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The incorporation of In in the growth of crescent‐shaped In0.12Ga0.88As quantum wires embedded in (AlAs)4(GaAs)8superlattice barriers is studied in atomic detail using cross‐sectional scanning tunneling microscopy. It is found that the In distribution in both the surface and the first subsurface layer can be atomically resolved in the empty‐ and filled‐state images, respectively. Strong In segregation is seen at the InGaAs/GaAs interfaces, but neither an expected enhancement of the In concentration at the center of the quantum wire compared to the planar quantum well nor In clustering beyond the statistical expectation is observed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114494

出版商:AIP    

年代:1995

数据来源: AIP