A practical method to determine the composition within ternary heterostructured semiconductor compounds using energy-dispersive X-ray spectroscopy in scanning transmission electron microscopy is presented. The method requires minimal external input factors such as user-determined or calculated sensitivity factors by incorporating a known compositional relationship, here a fixed stoichiometric ratio in III–V compound semiconductors. The method is demonstrated for three different systems; AlGaAs/GaAs, GaAsSb/GaAs, and InGaN/GaN with three different specimen geometries and compared to conventional quantification approaches. The method incorporates absorption effects influencing the composition analysis without the need to know the thickness of the specimen. Large variations in absorption conditions and assumptions regarding the reference area limit the accuracy of the developed method.

We present the first macroscopical model for charge transport in compound semiconductors to make use of analytic ellipsoidal approximations for the energy dispersion relationships in the neighbours of the lowest minima of the conduction bands. The model considers the main scattering mechanisms charges undergo in polar semiconductors, that is the acoustic, polar optical, intervalley non-polar optical phonon interactions and the ionized impurity scattering. Simulations are shown for the cases of bulk 4H and 6H-SiC.

The recent discovery of forward-voltage degradation in SiC pin diodes has created an obstacle to the successful commercialization of SiC bipolar power devices. Accordingly, it has attracted intense interest around the world. This article summarizes the progress in both the fundamental understanding of the problem and its elimination.The degradation is due to the formation of Shockley-type stacking faults in the drift layer, which occurs through glide of bounding partial dislocations. The faults gradually cover the diode area, impeding current flow. Since the minimization of stress in the device structure could not prevent this phenomenon, its driving force appears to be intrinsic to the material. Stable devices can be fabricated by eliminating the nucleation sites, namely, dissociated basal-plane dislocations in the drift layer.Their density can be reduced by the conversion of basal-plane dislocations propagating from the substrate into threading dislocations during homoepitaxy.

We describe how the material properties of III–V semiconductors, including bandgap, band structure, band offset, refractive index, absorption, and ionization coefficient, are exploited for lasers and photodetectors for fiber-optic communications. The material systems discussed for 1.3 μm and 1.55 μm light emission include the more traditional GaInAsP and AlGaInAs on InP, the more recently investigated GaInAs quantum dots and low-bandgap GaInNAs on GaAs as well as GaAsSb/GaAs Type II structures, and the potentially viable GaN/AlGaN from intersubband transitions (i.e., between quantized conduction-band energy levels). As an example of photodetector applications, GaInAsP/InP and wafer-fused GaInAs/Si are discussed in terms of gain and noise factor for use in avalanche photodiodes with separate absorption and multiplication regions.

GaAs-based continuous-wave quantum-dot vertical-cavity surface-emitting lasers (VCSELs) operating at 1.3 μm at 20°C with output power of 1.2 mW have been realized. Threshold currents approach 1–1.5 mA for 8-μm oxide apertures. Operating voltages are ∼2 V. Long operation lifetimes in excess of 5000 h at 50°C without degradation have been achieved. This article describes these breakthroughs, which are based on our development of complex self-organized growth technologies for defect-free stacked quantum dots.

Optical components based on vertical-cavity surface-emitting lasers (VCSELs) are moving from 850-nm wavelengths to 1.31-μm and 1.55-μm wavelengths. These long-wavelength devices, enabled by new developments in materials technology, will compete directly with distributed-feedback (DFB) and Fabry-Pérot (FP) laser technologies in fiber-optic markets. In addition, the unique properties of VCSELs are opening up a new category of optically integrated components that are not possible with traditional edge-emitting laser source technologies. These VCSEL structures, such as linear and two-dimensional arrays, have the potential to dramatically reduce the cost structure of traditional optical networking equipment and provide a path for rapid growth in optical bandwidth.

The emergence of miniature light sources such as the vertical-cavity surface-emitting laser (VCSEL) is poised to advance the information age. The development of VCSELs has stimulated a wide range of materials research into epitaxial growth and device-fabrication technologies. In this article, current and emerging applications that are guiding the commercial development of VCSELs are first considered, followed by discussions of the VCSEL epitaxial structure and fabrication technologies. This brief overview will also mention recent efforts aimed at achieving long-wavelength VCSELs grown on GaAs substrates, as well as approaches for achieving a high modulation rate.

Distributed Bragg reflectors (DBRs) not only serve as high-reflectance mirrors to define the laser cavity of a vertical-cavity surface-emitting laser (VCSEL), but they also must conduct electricity, confine currents, and provide a single-crystal template for the gain region of the laser. Basic optical and electrical properties of DBRs are presented in this article. Three examples of DBR structures used in VCSEL applications from the ultraviolet to the infrared are given to illustrate the complexity and range of materials science issues that are encountered in DBR growth. Fabrication issues are also discussed.