摘要:

Aninsitudry etching and metalorganic chemical‐vapor deposition regrowth process is developed to realize AlGaAs/GaAs buried heterostructure with an arbitrary shape and orientation, and is applied to edge‐emitting laser diodes with a complex cavity structure and surface‐emitting laser diodes (SELD). At present, threshold currents for both edge‐emitting and surface‐emitting lasers are similar to that of a conventional ridge‐stripe waveguide laser or proton‐isolated SELD, indicating that there is considerable surface recombination at regrown interfaces. Surface recombination velocity at the regrown interfaces is estimated from the size effect of lasing characteristics.

ISSN:0734-211X    

DOI:10.1116/1.588182

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Several chemical cleaning procedures for InSb(100) substrates were studied. Nomarski microscopy, x‐ray photoelectron spectroscopy, and Auger electron spectroscopy were used to assess their credibility for use in molecular beam epitaxial growth of high quality films. The most satisfactory substrate surface was prepared using a modified CP4A etchant (HNO3:CH3COOH:HF:DI H2O at 2:1:1:10). This etchant was found to produce a flat surface with low defect density and a passivating layer consisting mainly of easily removable Sb oxide.

ISSN:0734-211X    

DOI:10.1116/1.588184

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Sharp tips for various modern microscopies, such as field‐ion microscopy (FIM) and scanning tunneling microscopy (STM), can be prepared by electropolishing in solutions which are relatively innocuous for the environment as well as the researcher, compared to the often hazardous solutions still in widespread use. We have made measurements of polishing times as a function of solution and voltage parameters and we report conditions for electropolishing sharp tips of Pt, Ir, Au, Pd, and Rh using relatively benign solutions.

ISSN:0734-211X    

DOI:10.1116/1.588186

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

The effects of rapid thermal annealing on the electrical properties of ITO/n‐GaAs are investigated. For as‐deposited contacts the current is dominated by recombination at low bias and by thermionic emission at high bias. Annealing at 500 °C for 20 s causes the current to be dominated by thermionic emission for all biases. Annealing at 600 and 700 °C degrades the contact properties. At 700 °C annealing temperature the current is dominated by tunneling. Removal of sputter generated defects at low annealing temperature, diffusion of indium and tin atoms into GaAs and formation of ann+InAs–InxGa1−xAs layer at higher annealing temperature are proposed as mechanisms to explain the observations.

ISSN:0734-211X    

DOI:10.1116/1.588187

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

High‐brightness blue and green light‐emitting diodes (LEDs) operating at peak wavelengths in the range 489–514 nm have been successfully synthesized, processed, and tested. The high‐brightness LEDs are II‐VI heterostructures grown by molecular beam epitaxy at North Carolina State University using (100) ZnSe substrates produced at Eagle‐Picher Laboratory by the seeded physical vapor transport process. The blue LEDs (489 nm) produce 327 μW at 10 mA drive current with an external quantum efficiency of 1.3%. In terms of photometric units, the luminous performance of the ZnCdSe blue LEDs is 1.7 lm/W at 10 mA. The brightest ZnTeSe green LEDs tested to date produce 1.3 mW at 10 mA peaked at 512 nm with an external quantum efficiency of 5.3%. The luminous performance of the green LEDs is 18 lm/W at 10 mA. Using recently‐developedn‐type conducting ZnSe substrates, green LEDs having external quantum efficiencies of 2.7% have also been demonstrated.

ISSN:0734-211X    

DOI:10.1116/1.588188

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Two types of nitrogen plasma sources, an electron cyclotron resonance (ECR) plasma source and a radio frequency (rf) plasma source, were used for the growth of GaN by molecular beam epitaxy (MBE). GaN film quality was correlated with the optical emission characteristics of each type of nitrogen plasma source employed. The best quality GaN films were those grown using the rf nitrogen plasma source. This source was found to emit a much larger fraction of atomic nitrogen and 1st‐positive series excited molecular nitrogen in contrast to the ECR plasma source which mainly produced 2nd‐positive series excited molecular nitrogen and nitrogen molecular ions when operated under the same conditions. The benefit of homoepitaxial growth of GaN, using metalorganic vapor phase epitaxy grown GaN layers on basal plane 6H‐SiC, was seen by the observation of surface reconstructions before, during, and after GaN film growth by MBE. In addition, the MBE‐grown GaN films exhibited remarkably intense photoluminescence dominated by a sharp band‐edge peak at 3.409 eV having a full‐width at half‐maximum (FWHM) of 29.7 meV at room temperature. At lower temperatures, splitting of the near‐edge excition peaks was observed. Double‐crystal x‐ray rocking curve measurements of selected MBE‐grown GaN films yielded (0002) diffraction peaks having FWHMs as narrow as 156 arcsec.

ISSN:0734-211X    

DOI:10.1116/1.588189

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Transmission electron microscopy was used for the characterization of GaN epitaxial layers grown by molecular‐beam epitaxy on two different substrates: sapphire (Al2O3) and 6H‐SiC. GaN layers grown on both substrates crystallize with the wurtzite structure. Despite the very different lattice mismatch associated with their two substrates, similar types of defects were formed in the GaN layer; only their density differed. In addition to small‐angle subgrain boundaries two other types of defects were seen in cross‐sectioned samples: defects parallel to the growth surface and microtwins with a width of about 8–10 nm perpendicular to the growth surface. The parallel defects were identified as stacking faults leading to a local fcc atom arrangement in the layer and are believed to be growth defects. The density of these faults decreased with layer thickness. However, the density of the vertical microtwins remained constant through the layer. Slight local lattice twists between the microtwins and surrounding areas or differences of stoichiometry are suggested as an explanation for the observed contrast of the high‐resolution images.

ISSN:0734-211X    

DOI:10.1116/1.588190

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A modified molecular beam epitaxy technique has been used to grow single barrier GaAs/GaN/GaAs heterostructures of bothn‐ andp‐type. The temperature‐dependentI(V) measurements show thermally activated conduction over the barrier above about 200 K. A Type I band alignment is indicated by significant offsets in both the conduction and valence bands at the GaAs/GaN heterointerface.

ISSN:0734-211X    

DOI:10.1116/1.588191

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Layers of InN and GaN have been successfully grown on GaAs(001) and GaP(001) substrates using a modified molecular beam epitaxy technique. X‐ray diffraction data reveals that these layers are, in fact, separated into binary components of GaAs and mixtures of GaN in its hexagonal or zinc‐blende form. The same composite layers have also been studied with scanning electron microscopy, and we find a close correlation between the grain size measured from the scanning electron microscopy images and those determined from the full width at half‐maximum of the x‐ray diffraction spectra. This key observation demonstrates for the first time that there is a direct relationship between the measured x‐ray half‐widths and the microstructure of the films for both hexagonal and zinc‐blende polytypes. In addition, we have been able to control the growth conditions of GaN such that we can now selectively grow either exclusively hexagonal or zinc‐blende material.

ISSN:0734-211X    

DOI:10.1116/1.587861

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

We investigate the room temperature interface formation of the Na/carbon‐rich β‐SiC(100) surface by core level and valence band photoemission spectroscopy using synchrotron radiation. The deposition of a Na layer at saturation coverage results in surface metallization as evident from the presence of plasmon loss features at core levels, and from a Fermi edge building‐up in the valence band. Furthermore, large chemical shifts at both C 1sand Si 2pcore level indicate reactive interface formation and surface disruption with significant adsorbate–substrate charge transfer. The Na–Si bond establishment leads to subsequent breaking of the C–Si bonds leaving additional C atoms on the surface as carbon/graphite clusters. Exposure of the Na/β‐SiC(100) interface to a small amount of oxygen results in the removal of surface metallization.

ISSN:0734-211X    

DOI:10.1116/1.587862

出版商:American Vacuum Society    

年代:1995

数据来源: AIP