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We report on the room-temperature wafer-bonded InGaP/GaAs//InGaAsP/InGaAs four-junction solar cell grown by all solid-source molecular beam epitaxy (MBE). The material growth and structure optimization of multi-junction solar cell were investigated. The effect of growth temperature on phosphide-related material of the solar cell was discussed. The lattice-matched InGaP/GaAs tandem cell on GaAs substrate and InGaAsP- or InGaAsP/InGaAs-tandem cell on InP substrate were grown separately by MBE. Room-temperature wafer bonding technique was used to integrate the subcells into multi-junction solar cells. The current limiting of multi-junction cells was analysed and the device structure of four-junction solar cell was optimized. The best wafer-bonded four-junction solar cell reached a conversion efficiency of 42% under concentration.

The talk reviews progress on high-speed InGaAs/InP photodiodes on silicon-based photonic platforms. Recent results from heterogeneously integrated photodiodes based on adhesive die bonding and direct III-V material growth on Si will be discussed.

High-speed high-power photodiodes are key components in microwave photonic applications including antenna remoting, generation of microwave signals, and analog optical links. With the rapid emergence of Si photonics, it is becoming increasing important to develop approaches to incorporate these photodiodes into a Si platform. For integration of III-V photodiodes on silicon, various integration approaches have been reported, including adhesive wafer bonding, direct molecular wafer bonding, and direct III-V material growth on Si. This paper will report the integration of InGaAs/InGaAsP/InP modified uni-traveling carrier photodiodes using each of these techniques. In addition, high-power Ge on Si photodiodes will be discussed.

Similar simulation protocols are expected to be able to be used in studies of growth mechanisms of other 2D materials. Certainly, there are still many challenges in the study of two-dimensional material growth mechanism. For example, relaxation of the surface structure at very high temperatures may prohibit the use of lattice model in KMC simulations.

After the discovery of graphene, other two-dimensional (2D) layered crystals have attracted extensive attention because of their fundamental physical properties. Semiconducting 2D solids, such as transition metal dichalcogenides (TMDCs), has superior benefits in terms of the ultra-thin body, high mechanical strength, and thermal stability. Most importantly, a new material platform could overcome the performance of graphene with a sizable electronic gap. As expected, the materials have a variety of device applications. Atomically thin TMDC layer preparation and assembly have been combined for generating a van der Waals layered material due to lack of robust techniques for epitaxial growth. In spite of significant research efforts on material growth, large-scale growth with defect-free film quality remains a challenge. Here, we provide an overview of the traditional approach and recent progress in top-down methods such as vapor phase growth and solution processes. Layer-by-layer stacking of diverse material toward the realization of complex heterostructured devices is discussed. State-of-the-art assembling techniques with alternative methods are described.

Cadmium telluride-based solar cell is the most successfully commercialised thin film solar cell today. The laboratory-scale small devices have achieved ~ 22%, and commercial solar panels have reached ~ 18% conversion efficiencies. However, there are various technical complications and some notable scientific contradictions that appear in the scientific literature published since the early 1970s. This review paper discusses some of these major complications and controversies in order to focus future research on issues of material growth and characterisation, post-growth processing, device architectures and interpretation of the results. Although CdTe can be grown using more than 14 different growth techniques, successful commercialisation has been taken place using close-space sublimation and electrodeposition techniques only. The experimental results presented in this review are mainly based on electrodeposition. Historical trends of research and commercial successes have also been discussed compared to the timeline of novel breakthroughs in this field. Deeper understanding of these issues may lead to further increase in conversion efficiencies of this solar cell. Some novel ideas for further development of thin film solar cells are also discussed towards the end of this paper.

This talk reviews our recent work on material growth, device fabrication and application of terahertz quantum cascade lasers (THz QCLs).

Area-selective channel material growth for 2D transistors is more desirable for volume manufacturing than exfoliation or wet/dry transfer after large area growth. We demonstrate the first top-gate WS 2 p-channel field-effect transistors (p-FETs) fabricated on SiOx/Si substrate using channel area-selective CVD growth. Smooth and uniform WS 2 comprising approximately 6 layers was formed by area-selective CVD growth in which a patterned tungsten-source/drain served as the seed for WS 2 growth. For a 40 nm gate length transistor, the device has impressive electrical characteristics: on/off ratio of ~106, a S.S. of ~97 mV/dec., and nearly zero DIBL.

Three-dimensionally confined semiconductor quantum dots have emerged to be a versatile material system with unique physical properties for a wide range of device applications. With the advances in nanotechnology and material growth techniques for both epitaxial and colloidal quantum dots, recently the research has been shifted largely towards quantum dot based devices for practical applications. In this short review, we have tried to assemble a selection of recent advances in the areas of quantum dots for computing and communications, solid state lighting, photovoltaics, and biomedical applications that highlight the state of the art.

Photon management is essential in improving the performances of optoelectronic devices including light emitting diodes, solar cells and photo detectors. Beyond the advances in material growth and device structure design, photon management via nanoscaled phenomena have also been demonstrated as a promising way for further modifying/improving the device performance. The accomplishments achieved by photon management via nanoscaled phenomena include strain-induced polarization field management, crystal quality improvement, light extraction/harvesting enhancement, radiation pattern control, and spectrum management. In this review, we summarize recent development, challenges and underlying physics of photon management in GaN-based light emitting diodes and solar cells.

From humble beginnings, diode laser technology has evolved to become an invaluable tool for many aspects of our daily lives. Diode lasers exhibit a number of favorable properties which have led to their wide adoption, including compactness, robustness, and mass producibility. Just as important is the ability to engineer the emission wavelength and performance to be suitable for an application of interest. However, accomplishing this often requires significant innovation. A principal illustration of this was the development of 1.3 and 1.55 micron wavelength lasers for telecommunication, which required innovations in InP-based Quantum physics, atomic engineering, and material growth. Other examples include Al-free near infrared lasers for high efficiency solid state laser pumping and the III-Nitride materials for blue/violet laser diodes.

The talk reviews heterogeneously integrated InGaAs/InP photodiodes on silicon for analog photonics applications. Recent results from photodiodes based on molecular wafer bonding, adhesive die bonding, and direct III-V material growth on Si will be discussed and compared to their Ge-on-Si counterparts.

A second-gradient theory in finite strains is proposed to deal with the phenomena of material growth and remodeling, as happens in biomechanics, on account of mass transport and morphogenetic species. It involves first-order and second-order transplants (local structural rearrangements) and two material connections on the material manifold. It is shown that the evolution of these structural changes or “material inhomogeneities” is governed by Eshelby-like stress and hyperstress tensors. A thermodynamically admissible set of constitutive equations is proposed. The complexity due to the finite-strain gradient theory is a necessity in order to accommodate mass exchanges and diffusion of species.

In this paper, we review the history of the Center for Quantum Devices’ (CQD) III-nitride research covering the past 15 years. We review early work developing III-nitride material growth. We then present a review of laser and light-emitting diode (LED) results covering everything from blue lasers to deep UV LEDs emitting at 250 nm. This is followed by a discussion of our UV photodetector research from early photoconductors all the way to current state of the art Geiger-mode UV single photon detectors.

We report on the present status and future prospect of nano-carbon interconnect technologies, consisting of carbon nanotube (CNT) vertical interconnects (vias) and graphene horizontal interconnects, mainly in terms of material growth and fabrication process technologies to meet the requirement of process compatibility with a conventional Si LSI. Their superior electrical properties for replacing Cu interconnects are demonstrated.

In this paper, we report the development and performance of a complete InP-based DHBT manufacturable technology from material growth to device and integrated circuits realizations. The InGaAs/InP DHBTs were grown in a multi-wafer solid phosphorus MBE system. High frequency devices with an effective emitter area of 4.8 µm2 exhibited peak fT and fMAX values of 250 and 270 GHz, respectively, at a collector current density of ∼4 mA/µm2. Using this technology, distributed amplifiers and low power consumption selectors, have been successfully fabricated and tested above 80 Gbit/s. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Capacitance-related methods and electron spin resonance were used to study the deep-level centers formed in n-4H-SiC as a result of irradiation with 8-MeV protons. For the samples, Schottky diodes and p-n structures formed on the layers either obtained by sublimational epitaxy or produced commercially by CREE Inc. (United States) were used. It was found that the type of centers introduced by irradiation is independent of the technology of the material growth and the type of charged particles. On the basis of the results of annealing the defects and the data of electron spin resonance, the possible structure of the centers is suggested.

The present paper reviews recent achievements in the fabrication of diode lasers for the near-infrared range on GaAs substrates. 1.3??m light emitters are currently widely used in fibre-optic communication systems. GaAs-based devices are potentially advantageous compared to their InGaAsP counterparts in several aspects, such as improvement of thermal stability, possibility to grow vertical-cavity surface-emitting lasers in a single growth run and the use of large-area high-quality inexpensive GaAs substrates. Three main approaches have been suggested so far to achieve the 1.3??m emission from structures grown on GaAs substrates. They are InGaAs and GaAsSb quantum wells, GaInAsN quantum wells and InAs/GaAs quantum dots. In the present paper we discuss all these approaches including material growth, optical properties and laser characteristics. The results obtained by these methods are compared and their potential advantages discussed.

The 35 papers in this special issue describe some of the most recent and exciting work in solid-state lighting (SSL) technology. Categories include: material physics, material growth and processing, and novel substrates for SSL; physics and simulation of SSL device technology; and novel device concepts for SSL.

Silicon carbide technology has made tremendous strides in the last several years, with a variety of encouraging device and circuit demonstrations in addition to volume production of nitride-based blue LEDs being fabricated on SiC substrates. The commercial availability of relatively large, high quality wafers of the 6H and 4H polytypes of SiC for device development has facilitated these exciting breakthroughs in laboratories throughout the world. These have occurred in numerous application areas, including high power devices, short wavelength optoelectronic devices, and high power/high frequency devices. This paper will describe progress made in increasing the quality and size of SiC wafers, advances in SiC epitaxy and some of the resulting device demonstrations and commercialization by Cree Research.

We report a novel 1060-nm ridge waveguide high-power DFB laser, with a large optical cavity optimized for relaxing etched-depth processing tolerance, GaAs/AlGaAs grating for simplifying material growth and double-trench lateral leaky waveguide for mode stability.

Deep UV LED structures with UV transparent design, reflective p-electrodes and die encapsulation exhibited external quantum efficiency above 11%. Progress in material growth and device fabrication will be discussed along with issues further limiting efficiency.

The present manuscript addresses key issues in the course of our study of materials processing of bulk high-temperature superconductors, trapped flux and its application to a prototype axial-gap-type rotating machine. The TUMSAT group has conducted a series of studies since 2003 on the growth of GdBa2Cu3O7−δ bulk material and its application in a compact low-speed high-torque rotating machine. In the stage of material growth, gaining the advantage of a large motive torque density requires large integrated flux in the motor/generators. A large grain surface might be required with sophisticated techniques for the melt-growth texture in the bulk with optimal flux pinning. In the second stage, the in situ magnetization procedure for bulk superconductors in the applied machine is a crucial part of the technology. Pulsed current excitation by using an armature copper winding has magnetized field pole bulks on the rotor. The axial-gap flux synchronous machine studied in the past decade is a condensed technology and indicates that further scientific development is required for a future compact machine to be superior to conventional ones in accordance with the cryogenic periphery and flux stabilization.

The use of multicrystalline silicon solar cells has increased in the past decade because of its associated reduced cost and high efficiency. This paper discusses the various fabrication and characterization techniques that have been utilized in the advancement of multicrystalline silicon solar cells. The scientific understandings which helped to improve the cell efficiency from approximately 7% in 1980 to 20.3% in 2004 are discussed in this work. Additionally, this study provides an analysis of results of mc-Si solar cells that may lead to efficiency >18% in industrial mc-Si solar cells. An extensive evaluation from material growth to cell processing is also discussed. Although there is no direct relation between the influence of grain boundary or dislocation and solar cell performance, the understanding of its influence on various solar cell parameters has led to improvement in its performance.

This paper briefly presents some important aspects of the GaSb‐based material growth, as well as the performance of photodiodes and TPV devices for the 0.9–2.55 μm spectral range. A reproducible technique has been developed for the production of high‐speed and high‐efficiency GaSb/GaInAsSb/GaAlAsSb photodiodes. The detectivity of the photodiodes, estimated from the measured noise level and monochromatic current sensitivity, in the spectral peak reaches D*(λmax, 1000, 1)=(0.8–1.0)×1011 W−1×cm×Hz1/2 at room temperature. Recently, we have adapted the technology for creating GaInAsSb (0.52–0.53 eV band gap) TPV devices. Based on the our results we believe a 0.5 eV band gap GaSb‐based TPV cell with an open‐circuit voltage well over 300 mV at current 2–3 A is a realistic near‐term goal.

An overview of DRS' development of a very unique two-color infrared photodiode architecture for two-color infrared focal-plane arrays based on Hg 1-x Cd x Te is given. One unique feature of this architecture is that it requires only a mono-color based on Hg 1-x Cd x Te material growth technique for its implementation. Some data from this development are presented.

This paper summarizes the progress, trends, and technical issues associated with monolithic millimeter-wave integrated circuit technology. Presented first is background information which sets forth a description of the opportunities which spur this activity, and a summary of the important technical challenges. The technical challenges encompass aspects of: semicondutor material growth and processing; solid-state source performance; device and circuit characterization, de-embedding and modeling; and automated testing. Next, a discussion is provided of the semiconductor device types and circuit media which serve as building blocks for this technology. Device types treated here include sources, mixer/detectors, and modulators. The material offered relating to circuit media contrasts the attributes of monolithic approaches with those of waveguide and hybrid techniques. The paper concludes with a description of salient monolithic programs which benchmark the status of current effort in the U.S. This description includes a summary of important technical issues and research thrusts.

Great strides have been made in the area of Il-VI based short wavelength laser diodes since the first demonstration of pulsed blue-green lasers by 3M Company in 1991. These advances have been primarily due to a greater understanding of the material growth, including substrate preparation, the use of the MgZnSSe quaternary system, defect reduction, and p-type ohmic contacts.

Type II InAs/GaSb superlattice 1 has recently gained a lot of interest and is considered as a viable alternative to the HgCdTe technology in the long wavelength infrared (LWIR) detection.2 The material system is now entering a new development phase where the mass production and cost-effectiveness have become an important consideration. One immediate requirement is to achieve the high quality material on large size substrates, which can economize the material growth, reduce the fabrication cost, and especially allow the realization of large format imagers. The 2010 Edward G. Weston Summer Research Fellowship — Summary Report

This paper summarizes the technical characteristics and performance of our newly purchased VG V80H MBE system. Our research work on thin film semiconductor laser materials growth on this system has also been presented here, with some discussion on beam flux stability and growth uniformity et al.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The work described here was aimed towards high efficiency light emitting diodes (LEDs), thereby compromising on directionality and narrow spectrum. At present our efforts have yielded devices which have an external quantum efficiency (QE) of over 22%. This is believed to be a record QE for planar LEDs. This result relies on both careful design and material growth. For the design we developed a simulation tool which proves useful in selecting interesting structures and interpreting experimental results. The theoretical analysis includes the guided modes, reabsorption of light by the active material and subsequent photon recycling. The material is grown with MOVPE, which yields high quality material as well as allowing excellent control over layer thickness and composition. In the first part we highlight the main characteristics of the theoretical model and deal with some key issues in the design of high efficiency microcavity LEDs (MCLEDs). In part two the main experimental results are discussed.

Recent advances in material growth and lithography have made it possible to fabricate electronic structures with dimensions smaller than the so-called phase coherence length of electrons. In such structures electrons propagate without making any phase breaking collisions, hence the phases of the electron waves entering and leaving the structure are deterministically related. This is analogous to the situation in photonics, and one can envision fabricating electron waveguides. This opens up the possibility of creating new and novel devices drawing parallels from photonic devices and many such proposals have already been made [1], [2]. In this work we experimentally studied one such device, which is the analog of the Y branch in integrated optics also known as the digital switch [3].

This paper describes recent progress in the Ka-band MMIC power amplifier program. New materials, material growth techniques, device designs and circuit design techniques have made it possible to design and fabricate MMIC amplifiers with both high efficiency and high power at Ka-band and higher frequencies. MMIC amplifiers using pseudomorphic AlGaAs/InGaAs/GaAs HEMT devices presently achieve 400 mW with 25 percent efficiency at Ka-band and 1 W, 35 percent efficient amplifiers are being developed.

The young naturalist Ratzel supported himself by writing articles on his observations in Mediterranean and Alpine lands. These brought him the assignment to report on whatever interested him in the United States and Mexico (1873–1875). He returned from his American years to profess himself a geographer. Sketches of nature and the works and ways of men were followed by the large overview of his Culturgeographie of the United States during its first century. He liked the energy and expansiveness of American life, thought its excesses of wastefulness (Raubbau) a passing phase of youth, and had high expectation of its maturity. His observations and insights remained almost unnoticed in this country. A century later they give perspective on the dominance of material growth.

The letter describes the fabrication and assessment of indium phosphide devices designed for high peak-power pulsed operation at millimetre-wave frequencies. The importance of the cathode contact properties for this device are discussed, together with brief details of the n-n+ material growth parameters. An outline of the device fabrication technology is given before the resultant device RF performance characteristics are presented. It is shown that peak output powers as high as 1.2 W and DC to RF conversion efficiencies of up to 12% can be realised at 60 GHz.