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  • 1
    Digitale Medien
    Digitale Medien
    Transmission electron microscopy and transmission electron diffraction structural studies of heteroepitaxial InAsySb1−y molecular-beam epitaxial layers (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 8227-8236 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Molecular-beam epitaxy InAsySb1−y layers were grown at temperatures ranging from 295 to 470 °C across the full composition range. Transmission electron microscopy and transmission electron diffraction (TED) examinations showed that for layers grown at and below 400 °C with nominal compositions 0.4〈y〈0.8, separation into two phases occurred resulting in a series of alternating plates approximately parallel to the layer surface. TED showed that the cubic lattices of the two phases were tetragonally distorted and their compositions were deduced to be typically InAs0.38Sb0.62 and InAs0.72Sb0.28. The plates were larger and more regular along the [1¯10] direction than the [110] direction. As the growth temperature increased from 295 to 400 °C, for layers of nominal composition InAs0.5Sb0.5, the plate length increased from 0.1 to 2.0 μm and the plate thickness from 10 to 50 nm. Crystallographic defects were present in the layers and their occurrence was different in the phase-separated and non-phase-separated layers. The plates formed spontaneously at the growing surface and were stable during subsequent annealing at 350 and 370 °C. It is suggested that they arise due to the presence of a miscibility gap at these growth temperatures. We have termed these spontaneously grown plate structures "natural'' strained layer superlattices.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.353440
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  • 2
    Digitale Medien
    Digitale Medien
    Mechanisms for the reduction of the Schottky barrier heights of high-quality nonalloyed Pt contacts on surface-treated p-GaN (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 3064-3066 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: X-ray photoelectron spectroscopy (XPS) was employed to investigate the chemical bonding and electronic properties of the interfaces between Pt and p-GaN layers that were two-step surface treated using a buffered-oxide etch solution, and hence, to understand the surface-treatment time dependence of the Schottky barrier height (SBH). Current–voltage (I–V) measurements show that the effective SBH decreases with increasing surface-treatment time. The XPS results show that as the treatment time increases, the Ga 2p and Pt 4f core levels for the 20-min-treated samples shift toward the lower-binding-energy side by 0.6 and 1.5 eV, respectively, compared to the 0.5-min-treated one. It is further shown that the intensity of the oxygen core-level peak decreases with increasing treatment time. Based on the I–V and XPS results, the observed reduction of the effective SBHs is attributed to the combined effects of the effective removal of the native oxide and the shift of the surface Fermi level toward the valence-band edge. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1287236
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  • 3
    Digitale Medien
    Digitale Medien
    Atomic ordering and domain structures in metal organic chemical vapor deposition grown InGaAs (001) layers (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7852-7865 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Transmission electron microscope, transmission electron diffraction, and high resolution electron microscope studies have been made of metal organic chemical vapor deposition In0.53Ga0.47As layers grown on (001) InP or GaAs substrates to investigate the CuPt-type atomic ordering and associated microstructures present. The amount of ordering, the geometry of the (1¯11) and (11¯1) ordered domains, and the occurrence of anti-phase boundaries (APBs) were determined as a function of the layer growth temperature and rate. The results are interpreted in terms of mechanisms involving ordering at the layer surface and disordering in a transition region below the surface. From a consideration of the former it is concluded that atomic steps associated with surface undulations have a major influence on the domain geometry and APBs. The different structures that occur, their dependence on growth conditions and their possible effects on the electrical and optical properties are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.356569
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  • 4
    Digitale Medien
    Digitale Medien
    Low-resistance Pt/Ni/Au ohmic contacts to p-type GaN (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 70-72 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report on a Pt (20 nm) Ni (30 nm)/Au (80 nm) metallization scheme for low-resistance ohmic contacts to the moderately doped p-type GaN:Mg (3×1017 cm−3). Both as-deposited and annealed Pt/Ni/Au contacts on p-GaN exhibit linear current–voltage characteristics, showing that a high-quality ohmic contact is formed. The Pt/Ni/Au scheme shows the specific contact resistance of 5.1×10−4 Ω cm2 when annealed at 350 °C for 1 min in a flowing N2 atmosphere. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.123954
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  • 5
    Digitale Medien
    Digitale Medien
    Effects of thermal and hydrogen treatment on indium segregation in InGaN/GaN multiple quantum wells (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6514-6518 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The effects of indium segregation and hydrogen on the optical and structural properties of InGaN/GaN multiple quantum wells, grown by metalorganic chemical vapor deposition were investigated. Photoluminescence and high-resolution transmission electron microscopy analysis showed that two types of indium-rich regions can be formed in the InGaN well layers. Self-assembled quantum dot-like indium-rich regions were found in the well layer grown at a normal growth temperature. These regions behaved as luminescent centers, showing a maximum indium content at the center of indium-rich region. However, randomly-distributed indium-segregated regions, which formed near the upper interface of the InGaN well layers during the subsequent high-temperature annealing process led to the degradation of the optical properties by generating defects such as misfit dislocations. The use of hydrogen during the growth interruption was found to be very effective in suppressing the formation of indium-segregated regions in the InGaN well layers. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1370368
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  • 6
    Digitale Medien
    Digitale Medien
    Ultrahigh transparency of Ni/Au ohmic contacts to surface-treated p-type GaN (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5490-5492 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report on ultrahigh-transparency and low-resistance Ni/Au ohmic contacts to surface-treated p-GaN:Mg (3.6×1017 cm−3). It is shown that annealing at 500 °C for 1 min in a N2 ambient improves ohmic contact properties. Specific contact resistance is measured to be 5.0(±1.0)×10−3 and 2.5(±1.0)×10−3 Ω cm2 for the as-deposited and annealed samples, respectively. It is also shown that the light transmittance is 90.3(±0.6) and 97.3(±0.8) % (at 470 nm) for the as-deposited and annealed contacts, respectively. Furthermore, the surface of the annealed contact is found to be fairly smooth with a root-mean-square roughness of 0.84 nm. These results are compared with those previously reported for the Ni/Au contacts. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1312832
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  • 7
    Digitale Medien
    Digitale Medien
    Microstructures of GaN1−xPx layers grown on (0001) GaN substrates by gas source molecular beam epitaxy (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 3192-3197 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Transmission electron microscope (TEM), transmission electron diffraction (TED), and synchrotron x-ray diffraction (XRD) studies have been performed to investigate microstructural behavior of gas source molecular beam epitaxial GaN1−xPx layers grown on (0001) GaN/sapphire at temperatures (Tg) in the range 500–760 °C. TEM, TED, and XRD results indicate that the samples grown at Tg≤600 °C undergo phase separation resulting in a mixture of GaN-rich and GaP-rich GaNP with zinc-blende structure. However, the samples grown at Tg≥730 °C are found to be binary zinc-blende GaN(P) single crystalline materials. As for the 500 °C layer, the two phases are randomly oriented and distributed, whereas the 600 °C layer consists of phases that are elongated and inclined by 60°–70° clockwise from the [0001]α-GaN direction. The samples grown at Tg≥730 °C are found to consist of two types of microdomains, namely, GaN(P)I and GaN(P)II; the former having twin relation to the latter. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.369693
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  • 8
    Digitale Medien
    Digitale Medien
    Atomic ordering in molecular beam epitaxial InAsySb1−y natural strained layer superlattices and homogeneous layers (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3593-3595 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Transmission electron microscope studies were made of CuPt-type ordering in molecular beam epitaxial InAsySb1−y natural strained layer superlattices and homogeneous layers grown at temperatures in the range 295–470 °C. Ordering occurs with a maximum at a growth temperature of 370–400 °C, individual (1¯11) and (11¯1) ordered domains up to 10 nm in size are present, and there is a modulation of periodicity 3 d110 within the layers, where d110 is the (110) lattice spacing. The latter correlates with a [2×3] atomic surface reconstruction present during growth.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.111208
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  • 9
    Digitale Medien
    Digitale Medien
    Naturally formed InxAl1−xAs/InyAl1−yAs vertical superlattices (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3443-3445 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: InxAl1−xAs/InyAl1−yAs vertical superlattices (VS) were naturally formed by phase separation during the growth of InAlAs/InP layers at temperatures in the range 565–615 °C by metalorganic chemical vapor deposition. The VS lies perpendicular to the (001) growth plane. As the growth temperature increased from 565 to 615 °C, the VS decreased in thickness from ∼15 to ∼6 nm, and became less planar and uniform. Transmission electron diffraction results showed the occurrence of CuPt-type ordering in some of the layers. Band-gap reduction of ∼300 meV was observed in the InAlAs layers grown at temperatures ranging from 565 to 615 °C. Such a large reduction in band-gap energy was attributed to combined effects of the VS and CuPt-type ordering. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.115787
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  • 10
    Digitale Medien
    Digitale Medien
    Microstructual study of the alternating current bias-enhanced nucleation and growth of diamond on (001) silicon wafers (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 3368-3370 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The bias-enhanced nucleation (BEN) and growth of diamond by microwave plasma chemical vapor deposition have been investigated using transmission electron microscopy (TEM), transmission electron diffraction (TED), atomic force microscopy (AFM), and scanning electron microscopy (SEM) full stop TED results show epitaxial relations between SiC and Si, and diamond and SiC, which depend on the BEN time. The formation of highly oriented (001) diamond films is obtained after 25 min BEN, in which the heteroepitaxially oriented β-SiC and hence the heteroepitaxially oriented diamond crystallites play an important role. TEM reveals the β-SiC crystallites 2–10 nm in size and the diamond crystallites 5–30 nm across. As the nucleation time increases, the density of the β-SiC crystallites increases from ∼2.7×1011 to ∼1.6×1012 cm−2, while that of the diamond crystallites varies from ∼2.0×109 to ∼4.1×1010 cm−2. Discrepancy between the densities obtained using TEM and AFM is discussed. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.119173
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