摘要:

Epitaxial layers and superlattices of GaAsN/GaAs were grown by metalorganic molecular beam epitaxy using dimethylhydrazine, triethylgallium, and conventional arsenic sources. The incorporation of nitrogen into the solid was investigated as a function of the substrate temperature and the flux of dimethylhydrazine and modeled assuming formation of an adduct. Growth of GaAsN is characterized by an activation energy of 0.97 eV arising from a difference between activation energies of the adduct sticking coefficient,EB∼1.27 eV,and the adduct formation,EA∼0.3 eV.Nitrogen incorporation of 3&percent; is obtained at a growth temperature of 400 °C. High-resolution x-ray diffraction and photoluminescence data demonstrate excellent quality of epitaxial layers and superlattices grown with dimethylhydrazine. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121245

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Three-dimensional arrays of vertically stacked sidewall quantum wires are fabricated by molecular beam epitaxy on GaAs(311)Asubstrates patterned with 500-nm-pitch gratings. The cathodoluminescence spectra at low temperature are dominated by the emission from the quantum wires with narrow linewidth accompanied by a very weak emission from the connecting thin quantum wells due to localization of excitons at random interface fluctuations. When the carriers in the quantum well become delocalized at elevated temperature, only the strong emission from the quantum-wire array is observed revealing perfect carrier capture into the quantum wires without detectable thermal repopulation of the quantum well up to room temperature. Thus, unpreceded device quality of this quantum-wire structure is demonstrated. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121246

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Arsenic-doped GaN films were grown via metalorganic chemical vapor deposition using trimethylgallium, ammonia, and arsine precursors. The arsenic concentration increases from3×1016to5×1017 cm−3in response to a change in arsine mole fraction from3.3×102to3.2×104 ppm.The electron mobility increases with arsenic content reaching a maximum value of374 cm2/V sat 300 K. In addition, the integrated photoluminescence intensity exhibits a 35-fold increase in magnitude at 300 K. To explain these findings, a simple physical model is proposed in which arsenic “impurities” occupy otherwise vacant sites on both the gallium and nitrogen sublattices. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121247

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have investigated the photoexcited carrier dynamics inIn1−xGaxAs/GaAsquantum wells using the photoluminescence up-conversion technique. We found a unique capture process which was exceptional both in terms of the capture time and its temperature dependence. In the case of a specific quantum well with wide barriers, the photoluminescence rise time, a parameter which includes the overall capture time and the exciton formation time, was less than 600 fs instead of the expected few hundred picoseconds. We show in this work that this unusually rapid process is the result of the capture of the photoexcited carriers (or excitons) by impurities in the GaAs barriers, from where they resonantly tunnel into the quantum well. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121248

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Using first-principles all-electron band structure method, we have systematically calculated the natural band offsets&Dgr;Evbetween all II–VI and separately between III–V semiconductor compounds. Fundamental regularities are uncovered: for common-cation systems&Dgr;Evdecreases when the cation atomic number increases, while for common-anion systems&Dgr;Evdecreases when the anion atomic number increases. We find that coupling between anionpand cationdstates plays a decisive role in determining the absolute position of the valence band maximum and thus the observed chemical trends. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121249

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

InGaN multi-quantum-well-structure laser diodes (LDs) grown on GaN substrates were demonstrated. The LDs showed a small thermal resistance of 30 °C/W and a lifetime longer than 780 h despite a large threshold current density of7 kA/cm2.In contrast, the LDs grown on a sapphire substrate exhibited a high thermal resistance of 60 °C/W and a short lifetime of 200 h under room-temperature continuous-wave operation. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121250

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Epitaxially grown semiconductive Nb-dopedBaTiO3thin films with low electrical resistivity similar to that of the bulk single crystal were prepared by metal–organic chemical-vapor deposition. Thin films with 1.5–7.5 at. &percent; Nb content showedn-type semiconductor character. The films with 5.7 at. &percent; Nb content showed the lowest resistivity,2.8×10−2 &OHgr; cm.This value is three orders of magnitude lower than those reported for sintered of Nb-dopedBaTiO3,and similar to that of Nb-dopedBaTiO3single crystals. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121251

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report far-infrared photoconductivity in self-organized InAs/GaAs quantum dots grown by molecular beam epitaxy. Through use of a Fourier transform infrared spectrometer, a photoconductivity signal peaked at 17 &mgr;m is observed from an–i–ndetector structure with doped InAs quantum dots in the intrinsic region. Comparison of photoluminescence and band-to-band photocurrent absorption spectra suggests the far-infrared response is due to intersubband transitions in the quantum dots. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121252

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We demonstrate the possibility to fabricate nuclear radiation detectors operating at room temperature from CdTe substrates affected by the vapor phase epitaxy (VPE) growth ofHg1−xCdxI2layers. The VPE layers with the thickness 10–30 &mgr;m were grown using an&agr;-HgI2polycrystalline source at 220 °C and time in the range of 30–100 h. The as-grown heterostructures were chemically etched to remove the epilayers, and Au–CdTe–Au detectors were made. The substrates were characterized by synchrotron x-ray topography before and after the VPE growth, and the current–voltage(I–V)and spectroscopic measurements of the detectors were carried out. The effect of the VPE growth on the substrates and detectors has been studied and on the basis of this it has been possible to fabricate &ggr;-ray detectors with OhmicI–Vcharacteristic and good spectral response. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121253

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Room temperature free carrier concentrations exceeding1×1018 cm−1have been achieved with 1000 °C implants into 4H–SiC using N and Al (1×1017 cm−3using B). A decrease in resistivity is observed for annealing temperatures above∼1300,∼1500,and∼1750 °Cfor N, Al, and B, respectively. Rutherford backscattering spectroscopy measurements indicate almost complete recrystallization for N-implanted samples and partial recrystallization on the silicon, but not the carbon, sublattice for B- and Al-implanted samples. An implant and species related step formation is also observed. Only boron is observed to diffuse appreciably. A crystal stoichiometry and Fermi level dependent model is proposed to explain the activation results. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121681

出版商:AIP    

年代:1998

数据来源: AIP