摘要:

Rapid thermal annealing of GaN in an Ar or N2ambient up to 1100 °C is shown to improve surface morphology and photoluminescence intensity. For both ambients the average rms surface roughness as determined by atomic force microscopy decreases from ∼4 nm on the as‐grown material to ∼1 nm after a 1100 °C anneal. The band‐edge luminescence intensity was increased by a factor of 4 after a 1100 °C anneal in a N2ambient and a factor of 2 for annealing at 1100 °C in an Ar ambient as compared to as‐grown material. The 1100 °C anneal improves the ratio of band edge to deep‐level luminescence and also reduces the electron concentration and mobility. The reduction in mobility can be explained in terms of a two‐band conduction mechanism where defect band conduction dominates at the lower carrier densities or an increase in the free‐carrier compensation ratio. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116459

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report a new photoluminescence (PL) spectrum of wurzite‐type GaN intentionally doped with vanadium by ion implantation. A group of several broad intense near‐infrared PL lines is observed at 820 meV. The whole PL spectrum can be observed up to room temperature. The samples were grown by low‐pressure metalorganic vapor phase epitaxy on sapphire substrate. After ion implantation the samples were annealed under growth conditions at 920 °C. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116460

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We investigated the temperature effect on exciton localization in self‐organized InAs quantum dots. Quenching energy for excitons in reference quantum well and quantum dots was found to be 2 and 7 meV, respectively. Thermoactivation energy of electron‐hole emission through a GaAs barrier in the quantum dots was measured as 46 meV. We observed an unusual decrease of photoluminescence peak full width at half maximum with temperature, suggesting suppression of nonpredominant size quantum dot emissions due to carrier tunneling between nearby dots. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116461

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We demonstrate the metalorganic chemical vapor deposition (MOCVD) growth of two‐dimensional electron gases (2DEGs) with electron mobilities up to 2.0×106cm2/V s at 0.3 K. These are the highest mobilities to date for MOCVD materials, and were achieved using a safer replacement precursor for arsine, tertiarybutylarsine (TBA). For structures grown using arsine, we obtained a maximum mobility of 1.0×106cm2/V s, which although comparable to the best by MOCVD to date, is half that obtained using TBA. Our studies on thick GaAs and AlGaAs layers indicate that the use of TBA in place of arsine reduces both the carbon and donor impurity concentrations. Thus, TBA is not only a safe alternative to arsine, but also produces significantly purer films. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116462

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Far infrared photoconductivity spectra of B‐doped Si1−xGexgrown by Czochralski technique have been investigated in the temperature region from 4.2 to 34 K as well as under high magnetic fields. The photo ionization transition from the ground state of boron acceptor toP3/2valence band and that related to spin‐orbit splitting valence band (P1/2) are observed. The experimental results show that the ionization energy of boron acceptor in Si1−xGexdecreases fast and linearly with the increase of Ge concentration for lower Ge composition, and 4% Ge contents make a decrease of 14 meV for the ionization energy of boron in Si0.96Ge0.04. The photoconductivity spectra hardly change with magnetic field up to 11 T. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116463

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Precipitation behaviors of Cu and Fe on Frank‐type partial dislocations bounding bulk stacking faults in Czochralski‐grown silicon are investigated by means of the electron beam‐induced‐current (EBIC) technique and transmission electron microscopy (TEM). Frank partials in a Cu‐contaminated specimen do not exhibit an EBIC contrast at room temperature when the specimen is cooled slowly; however, in the Fe‐contaminated specimen, they exhibit EBIC contrast at room temperature due to their Fe contamination. The TEM micrograph shows that Cu develops precipitate colonies in the region away from stacking faults and does not precipitate on Frank partials in the specimen. The results indicate that Fe impurity decorates Frank partials more easily than Cu impurity in Si. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116464

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We present a photoemission investigation of the interface between In and 3, 4, 9, 10 perylenetetracarboxylic dianhydride (PTCDA). The interfacial region is very wide due to an anomalously fast diffusion of In into the organic layer. In also reacts with the anhydride end groups of the molecules. The absence of metal clustering, which permits diffusion, is believed to be due to the ionization of In and ion–ion repulsion in the PTCDA matrix. Finally, the ohmicity of the In/PTCDA contact is attributed to reaction‐induced electronic gap states created throughout the wide interfacial region upon formation of the interface. This study provides the first direct correlation between chemistry and electronic properties of a metal contact on an organic molecular semiconductor. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116465

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have observed a degradation in the epitaxial layer quality of AlInAs when it is grown by molecular beam epitaxy at a substrate temperature of about 400 °C compared to that for alloys grown at 300 and 500 °C. The barrier height and ideality factor of Ti– and Au–AlInAs Schottky diodes also exhibit large spatial variations and dependence on growth temperatures. The observed phenomena can be explained by invoking a kinetic growth model or thermodynamic phase equilibria in the growing surface layer. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116466

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Combining low‐voltage electron beam lithography (EBL) and wet chemical etching, arrays of deep etched InGaAs/GaAs quantum wires with widths down to 15 nm and dots with minimum diameters of 27 nm have been fabricated. The application of low‐voltage EBL strongly reduces the proximity effect during pattern exposure and allows the formation of very homogeneous nanostructure arrays. Low‐excitation photoluminescence (PL) spectroscopy of both wires and dots reveals a structure size dependent blue shift of the emission lines up to 14 meV. This energy shift is caused by lateral confinement and shows a clear dependence on the structure dimensionality. The quantization is calculated with a simple model using only standard InGaAs/GaAs material parameters and the geometrical structure widths measured with a scanning electron microscope (SEM). ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116467

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A low thermal budget emitter contact with low specific contact resistivity (&rgr;c) with the absence of transient enhanced diffusion (TED) effects is essential to fabricate integratable high performance Si/SiGe heterojunction bipolar transistors (HBTs). We report the use ofinsituAs‐doped polycrystalline silicon (polysilicon) from a low base pressure rapid thermal episystem for this purpose and find that it meets all the requirements. We used secondary ion mass spectrometry to find that 18 nm, heavily B‐doped layers remain intact after implantation into the surface polysilicon and annealing at 800 °C for 40 s. Similar samples without the surface polylayer displayed extreme broadening of B profile. Kelvin crossbridge resistors together with 2D device simulations revealed that &rgr;cis an extremely low value of 1.2×10−8&OHgr; cm2in as‐deposited material. Fabrication of simple 30×30 &mgr;m2mesa isolated HBT devices showedICto be more than two decades higher in devices with only aninsituAs‐doped polyemitter compared with devices that incorporated a surface implant into the single crystal portion of the emitter before polysilicon deposition. These results demonstrate that this doped polycrystalline silicon material is an excellent choice for emitter contacts to HBT devices. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116468

出版商:AIP    

年代:1996

数据来源: AIP