Semiconductor heterostructures with modulated composition and/or doping enable passivation of interfaces and the generation of devices with diverse functions. In this regard, the control of interfaces in nanoscale building blocks with high surface area will be increasingly important in the assembly of electronic and photonic devices. Core-shell heterostructures formed by the growth of crystalline overlayers on nanocrystals offer enhanced emission efficiency, important for various applications. Axial heterostructures have also been formed by a one-dimensional modulation of nanowire composition and doping. However, modulation of the radial composition and doping in nanowire structures has received much less attention than planar and nanocrystal systems. Here we synthesize silicon and germanium core-shell and multishell nanowire heterostructures using a chemical vapour deposition method applicable to a variety of nanoscale materials. Our investigations of the growth of boron-doped silicon shells on intrinsic silicon and silicon-silicon oxide core-shell nanowires indicate that homoepitaxy can be achieved at relatively low temperatures on clean silicon. We also demonstrate the possibility of heteroepitaxial growth of crystalline germanium-silicon and silicon-germanium core-shell structures, in which band-offsets drive hole injection into either germanium core or shell regions. Our synthesis of core-multishell structures, including a high-performance coaxially gated field-effect transistor, indicates the general potential of radial heterostructure growth for the development of nanowire-based devices.

https://cml.harvard.edu/assets/nature420_57.pdf

Epitaxial core–shell and core–multishell nanowire heterostructures

Wide bandgap semiconductors show superior material properties enabling potential power device operation at higher temperatures, voltages, and switching speeds than current Si technology. As a result, a new generation of power devices is being developed for power converter applications in which traditional Si power devices show limited operation. The use of these new power semiconductor devices will allow both an important improvement in the performance of existing power converters and the development of new power converters, accounting for an increase in the efficiency of the electric energy transformations and a more rational use of the electric energy. At present, SiC and GaN are the more promising semiconductor materials for these new power devices as a consequence of their outstanding properties, commercial availability of starting material, and maturity of their technological processes. This paper presents a review of recent progresses in the development of SiC- and GaN-based power semiconductor devices together with an overall view of the state of the art of this new device generation.

A Survey of Wide Bandgap Power Semiconductor Devices

An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

Zinc oxide (ZnO) is a wide band gap semiconductor with potential applications in optoelectronics, transparent electronics, and spintronics. The high efficiency of UV emission in this material could be harnessed in solid-state white lighting devices. The problem of defects, in particular, acceptor dopants, remains a key challenge. In this review, defects in ZnO are discussed, with an emphasis on the physical properties of point defects in bulk crystals. As grown, ZnO is usually n-type, a property that was historically ascribed to native defects. However, experiments and theory have shown that O vacancies are deep donors, while Zn interstitials are too mobile to be stable at room temperature. Group-III (B, Al, Ga, and In) and H impurities account for most of the n-type conductivity in ZnO samples. Interstitial H donors have been observed with IR spectroscopy, while substitutional H donors have been predicted from first-principles calculations but not observed directly. Despite numerous reports, reliable p-t...

Defects in ZnO

The fact that wide bandgap semiconductors are capable of electronic functionality at much higher temperatures than silicon has partially fueled their development, particularly in the case of SiC. It appears unlikely that wide bandgap semiconductor devices will find much use in low-power transistor applications until the ambient temperature exceeds approximately 300/spl deg/C, as commercially available silicon and silicon-on-insulator technologies are already satisfying requirements for digital and analog VLSI in this temperature range. However practical operation of silicon power devices at ambient temperatures above 200/spl deg/C appears problematic, as self-heating at higher power levels results in high internal junction temperatures and leakages. Thus, most electronic subsystems that simultaneously require high-temperature and high-power operation will necessarily be realized using wide bandgap devices, once they become widely available. Technological challenges impeding the realization of beneficial wide bandgap high ambient temperature electronics, including material growth, contacts, and packaging, are briefly discussed.

High-temperature electronics - a role for wide bandgap semiconductors?

3-Inch-Siliciumcarbidwafer mit einer niedrigen Schraubenversetzung von 1 c

PROBLEM TO BE SOLVED: To provide micropipe-free single-crystal silicon carbide (SiC) and a method for producing the same.SOLUTION: A sublimation system 12 grows a SiC crystal 26 on a seed material 22 by placing a source material 20 and the seed material 22 in a reaction crucible 14 of the sublimation system 12 and placing the seed material 22 on a seed holder 24 inside the reaction crucible 14. Components of the sublimation system 12 including the source material 20, the reaction crucible 14, and the seed holder 14 are substantially free from unintentional impurities. By controlling a growth temperature, a growth pressure, a SiC sublimation flux and its composition, and a temperature gradient between the source material 20 and the seed material 22 or the SiC crystal 26 growing on the seed material 22, during a PVT process, micropipe-inducing process instability is eliminated and a micropipe-free SiC crystal is grown on the seed material 22.

Micropipe-free silicon carbide and method for producing the same

PROBLEM TO BE SOLVED: To solve the problems in a conventional technology for obtaining an off-axis wafer, wherein a larger crystal is generally oriented separately from a vertical line of the crystal, then, in order to produce an off-axis seed crystal, a wafer is cut toward the orientation direction, and orientation of the crystal in the separated state from the vertical line reduces a utilizable effective layer thickness because a wafer having the same size as the crystal is cut.SOLUTION: A semiconductor crystal and associated growth method are disclosed. The crystal includes a seed crystal portion and a growth portion on the seed crystal portion. The seed crystal portion and the growth portion form a substantially upright cylindrical single crystal of silicon carbide. A seed crystal face defines an interface between the growth portion and the seed crystal portion, with the seed crystal face being substantially parallel to the bases of the upright cylindrical crystal and being off-axis with respect to a basal plane of the single crystal. The growth portion replicates the polytype of the seed crystal portion and the growth portion has a diameter of at least about 100 mm.

ONE HUNDRED MILLIMETER SiC CRYSTAL GROWN ON OFF-AXIS SEED CRYSTAL

Carbure de silicium sans micro-tuyaux et procédé de fabrication correspondant

A high quality single crystal wafer of SiC is disclosed having a diameter of at least about 3 inches and a 1 c screw dislocation density from about 500 cm−2 to about 2000 cm−2.

Adrian Powell

Papers

3-Inch-Siliciumcarbidwafer mit einer niedrigen Schraubenversetzung von 1 c

Micropipe-free silicon carbide and method for producing the same

ONE HUNDRED MILLIMETER SiC CRYSTAL GROWN ON OFF-AXIS SEED CRYSTAL

Carbure de silicium sans micro-tuyaux et procédé de fabrication correspondant

WITHDRAWN PATENT AS PER THE LATEST USPTO WITHDRAWN LISTLow 1C screw dislocation 3 inch silicon carbide wafer

Adrian Powell

Papers

3-Inch-Siliciumcarbidwafer mit einer niedrigen Schraubenversetzung von 1 c

Micropipe-free silicon carbide and method for producing the same

ONE HUNDRED MILLIMETER SiC CRYSTAL GROWN ON OFF-AXIS SEED CRYSTAL

Carbure de silicium sans micro-tuyaux et procédé de fabrication correspondant

***WITHDRAWN PATENT AS PER THE LATEST USPTO WITHDRAWN LIST***Low 1C screw dislocation 3 inch silicon carbide wafer

WITHDRAWN PATENT AS PER THE LATEST USPTO WITHDRAWN LISTLow 1C screw dislocation 3 inch silicon carbide wafer