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The Ge2Sb2Te5 thin films deposited by a sputtering method on SiO2/Si substrates were annealed through a rapid thermal annealing process and performed a high-resolution transmission electron microscopy study in order to investigate the atomic arrangement of the metastable Ge2Sb2Te5. The metastable rocksalt structure having face-centered-cubic lattice was confirmed by high-resolution transmission electron microscopy images and simulated images on the directions of <100>, <110>, and <211> zone axes. According to the position of Ge and Sb in the metastable rocksalt structure, the atomic distribution alters when observed in different direction and this causes change in the charge-density distribution, resulting in different images in a high-resolution transmission electron microscopy. It is expected that as the crystallization proceeds, the Ge and Sb atoms tend to position themselves on a specific plane. From this aspect, the ordered structure model of the metastable Ge2Sb2Te5 was proposed by varying the position of the Ge and Sb atoms. [ABSTRACT FROM AUTHOR]

The effects of InGaAs/GaNAs barrier combinations were investigated in the metal organic vapor phase epitaxy grown GaInNAs quantum wells (QWs). Significant improvement was made in the optical performance of the 1.3 μm range with the proposed structures. Structural investigation linked with the optical properties reveals that a thin InGaAs layer, placed between GaInNAs QWs and GaNAs layers, plays a role in redistributing the nitrogen within the QWs while maintaining a sharp interface. The amount of diffused nitrogen is proportional to the strain residing in the InGaAs layer, which explains the tendency of blueshift with the increase in GaNAs thickness. [ABSTRACT FROM AUTHOR]

Presents a study which derived an equivalent noise source with a useful functional form for Boltzmann transport equations from the classical expression of the noise source. Methods used in understanding the noise phenomena in semiconductor devices; Mathematical expression for n-type nondegenerate semiconductor; Discussion on the controversy over correctness of an equation of the spectral intensity of the noise source.

Focuses on a study which reinvestigated the steady-state Nyquist theorem for multi-terminal semiconductor devices and its application to minimum noise figure in microwave field effect transistors. Discussion on the existing thermal noise theories for multi-terminal semiconductor devices; Methodology of the study; Results and discussion.

Deals with a steady-state Nyquist theorem for multi-terminal nondegenerate semiconductor devices. Derivation of formulas for the spectral intensities of the short-circuit thermal noise currents in arbitrarily shaped multi-terminal semiconductor devices under direct current bias; Experimental details; Result of the study.

We compared the structural and optical properties of InAs/GaAs quantum dots grown by migration enhanced epitaxy, with and without arsenic, during indium deposition. The uniformity and size of the quantum dots are enhanced in a sample without arsenic. As a result, narrower and longer wavelength photoluminescence is observed in this sample. Furthermore, the thickness of the wetting layers is reduced by ∼20% in the sample without arsenic, and this result agrees well with the speculation that metallic indium has a smaller driving force for corrugating the InAs wetting layers before they are transformed from two-dimensional to three-dimensional layers. Additionally, the photoluminescence linewidth of the sample without arsenic is insensitive to the cryostat temperature due to two major factors: the reduced thickness of the wetting layers and the enhanced uniformity. In the sample with arsenic, however, the photoluminescence linewidth shows typical anomalies. [ABSTRACT FROM AUTHOR]

The authors analyzed radiative efficiency of InGaN laser diodes (LDs) emitting at 405 nm. Based on semiconductor rate equations, the radiative efficiency is unambiguously determined by the analysis of electroluminescence characteristics. The radiative efficiency exceeds 70% even far below threshold of ∼3 mA at a high temperature of 80 °C. This highly radiative characteristic is attributed to reduced contribution of nonradiative recombination in LDs with low-dislocation-density active material. It is also found that the radiative efficiency is almost independent of threshold current, indicating that nonradiative recombination is not a major factor which determines lasing threshold in 405 nm emitting InGaN LDs having low dislocation density. [ABSTRACT FROM AUTHOR]

Transition related to the Mn–Zn interaction was observed in photoluminescence (PL) study of the InMnP:Zn epilayer and the peak position blueshifted with increasing Mn concentration. X-ray photoelectron spectroscopy was used to clarify the blueshift of the PL peak. The binding energy shifts of Mn 2p and Zn 2p core levels indicative of the interaction between Mn and Zn were observed. This mutual interaction between Mn 2p and Zn 2p agrees with the result that the Mn-related transition in InMnP:Zn codoped with Zn is shifted to the higher energy region in comparison with InMnP without additional doping of Zn. [ABSTRACT FROM AUTHOR]

We report a high power fundamental transverse mode operation of an optically pumped 1060 nm vertical-external-cavity surface-emitting laser. A diamond heat spreader was capillary bonded to the semiconductor surface. A 10 W continuous wave operation with optical-to-optical conversion efficiency of 44% was achieved at room temperature. The thermal rollover was not found up to a heat sink temperature of 60 °C. High efficiency and good thermal stability were mainly due to the optimization of epitaxial quality and the high conductivity of the diamond heat spreader. We have found that the increase of the round trip loss caused by the heat spreader was about 1%. [ABSTRACT FROM AUTHOR]