As such, SiC will continue to play a major role in the production of future super-bright visible emitters.
Especially substrates of the 3C polytype promise good quality, single crystalline GaN films~\cite{takeuchi91,yamamoto04,ito04,haeberlen10}.
-The focus of SiC based applications, however, is in the area of solid state electronics experiencing revolutionary performance improvements enabled by its capabilities~\cite{wesch96,morkoc94,casady96,capano97,pensl93,park98,edgar92,sarro00}.
-These devices include ultraviolet (UV) detectors, high power radio frequency (RF) amplifiers, rectifiers and switching transistors as well as microelectromechanical system (MEMS) applications.
+The focus of SiC based applications, however, is in the area of solid state electronics experiencing revolutionary performance improvements enabled by its capabilities~\cite{wesch96,morkoc94,casady96,capano97,pensl93,park98,edgar92}.
+These devices include ultraviolet (UV) detectors~\cite{brown93,yan04}, high power radio frequency (RF) amplifiers, rectifiers and switching transistors~\cite{pribble02,baliga96,weitzel96,zhu08,bhatnagar92,bhatnagar93,ryu01} as well as microelectromechanical system (MEMS) applications~\cite{sarro00}.
For UV detectors the wide band gap is useful for realizing low photodiode dark currents as well as sensors that are blind to undesired near-infrared wavelengths produced by heat and solar radiation.
These photodiodes serve as excellent sensors applicable in the monitoring and control of turbine engine combustion.
The low dark currents enable the use in X-ray, heavy ion and neutron detection in nuclear reactor monitoring and enhanced scientific studies of high-energy particle collisions as well as cosmic radiation.
Since the vapor pressure of Si is much higher than that of C, a careful manipulation of the Si vapor content above the seed crystal is required.
Additionally, to preserve epitaxial growth conditions, graphitization of the seed crystal has to be avoided.
Avoiding defects constitutes a major difficulty.
-These defects include growth spirals (stepped screw dislocations), subgrain boundaries and twins as well as micropipes (micron sized voids extending along the c axis of the crystal) and 3C inclusions at the seed crystal in hexagonal growth systems.
+These defects include growth spirals (stepped screw dislocations), subgrain boundaries and twins as well as micropipes (micron sized voids extending along the
+%c axis of the crystal)
+core of screw dislocations)~\cite{frank51,heindl97}
+and 3C inclusions at the seed crystal in hexagonal growth systems.
Micropipe-free growth of 6H-SiC has been realized by a reduction of the temperature gradient in the sublimation furnace resulting in near-equilibrium growth conditions in order to avoid stresses, which is, however, accompanied by a reduction of the growth rate~\cite{schulze98}.
Further efforts have to be expended to find relations between the growth parameters, the kind of polytype and the occurrence and concentration of defects, which are of fundamental interest and might help to improve the purity of the bulk materials.
APB defects, which constitute the primary residual defects in thick layers, are formed near surface terraces that differ in a single-atom-height step resulting in domains of SiC separated by a boundary, which consists of either Si-Si or C-C bonds due to missing or disturbed sublattice information~\cite{desjardins96,kitabatake97}.
However, the number of such defects can be reduced by off-axis growth on a Si \hkl(0 0 1) substrate miscut towards \hkl[1 1 0] by \unit[2]{$^{\circ}$}-\unit[4]{$^{\circ}$}~\cite{shibahara86,powell87_2}.
This results in the thermodynamically favored growth of a single phase due to the uni-directional contraction of Si-C-Si bond chains perpendicular to the terrace steps edges during carbonization and the fast growth parallel to the terrace edges during growth under Si rich conditions~\cite{kitabatake97}.
+% more up2date paper
+A reduction of the SF in addition to the APB defects was recently achieved by growing 3C-SiC on undulant Si~\cite{nagasawa06}, i.e.\ a Si \hkl(0 0 1) substrate covered with continuous slopes oriented in the \hkl[1 1 0] and \hkl[-1 -1 0] directions.
+In this way, APB defects are eliminated by a mechanism similar to that in the off-axis growth process while, at the same time, SFs are aligned in the \hkl(1 1 1) or \hkl(-1 -1 1) planes and, thus, terminate as they connect with each other during the growth process.
+%
By MBE, lower process temperatures than these typically employed in CVD have been realized~\cite{hatayama95,henke95,fuyuki97,takaoka98}, which is essential for limiting thermal stresses and to avoid resulting substrate bending, a key issue in obtaining large area 3C-SiC surfaces.
In summary, the almost universal use of Si has allowed significant progress in the understanding of heteroepitaxial growth of SiC on Si.
However, mismatches in the thermal expansion coefficient and the lattice parameter cause a considerably high concentration of various defects, which is responsible for structural and electrical qualities that are not yet satisfactory.
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