We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.

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Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems

In the past several years, research in each of the wide‐band‐gap semiconductors, SiC, GaN, and ZnSe, has led to major advances which now make them viable for device applications. The merits of each contender for high‐temperature electronics and short‐wavelength optical applications are compared. The outstanding thermal and chemical stability of SiC and GaN should enable them to operate at high temperatures and in hostile environments, and also make them attractive for high‐power operation. The present advanced stage of development of SiC substrates and metal‐oxide‐semiconductor technology makes SiC the leading contender for high‐temperature and high‐power applications if ohmic contacts and interface‐state densities can be further improved. GaN, despite fundamentally superior electronic properties and better ohmic contact resistances, must overcome the lack of an ideal substrate material and a relatively advanced SiC infrastructure in order to compete in electronics applications. Prototype transistors have been fabricated from both SiC and GaN, and the microwave characteristics and high‐temperature performance of SiC transistors have been studied. For optical emitters and detectors, ZnSe, SiC, and GaN all have demonstrated operation in the green, blue, or ultraviolet (UV) spectra. Blue SiC light‐emitting diodes (LEDs) have been on the market for several years, joined recently by UV and blue GaN‐based LEDs. These products should find wide use in full color display and other technologies. Promising prototype UV photodetectors have been fabricated from both SiC and GaN. In laser development, ZnSe leads the way with more sophisticated designs having further improved performance being rapidly demonstrated. If the low damage threshold of ZnSe continues to limit practical laser applications, GaN appears poised to become the semiconductor of choice for short‐wavelength lasers in optical memory and other applications. For further development of these materials to be realized, doping densities (especially p type) and ohmic contact technologies have to be improved. Economies of scale need to be realized through the development of larger SiC substrates. Improved substrate materials, ideally GaN itself, need to be aggressively pursued to further develop the GaN‐based material system and enable the fabrication of lasers. ZnSe material quality is already outstanding and now researchers must focus their attention on addressing the short lifetimes of ZnSe‐based lasers to determine whether the material is sufficiently durable for practical laser applications. The problems related to these three wide‐band‐gap semiconductor systems have moved away from materials science toward the device arena, where their technological development can rapidly be brought to maturity.

Large‐band‐gap SiC, III‐V nitride, and II‐VI ZnSe‐based semiconductor device technologies

Wide bandgap semiconductors are extremely attractive for the gamut of power electronics applications from power conditioning to microwave transmitters for communications and radar. Of the various materials and device technologies, the AlGaN/GaN high-electron mobility transistor seems the most promising. This paper attempts to present the status of the technology and the market with a view of highlighting both the progress and the remaining problems.

AlGaN/GaN HEMTs-an overview of device operation and applications

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

A monollithic CMOS integrated device formed in silicon carbide and method of fabricating same. The CMOS integrated device includes a layer of silicon carbide of a first conductivity type with a well region of a second conductivity type formed in the layer of silicon carbide. A MOS field effect transistor is formed in the well region and a complementary MOS field effect transistor is formed in the silicon carbide layer. The method of fabrication of CMOS silicon carbide includes formation of an opposite conductivity well region in a silicon carbide layer by ion implantation. Source and drain contacts are also formed by selective ion implantation in the silicon carbide layer and the well region. A gate dielectric layer is formed by deposition and reoxidation. A gate electrode is formed on the gate dielectric such that a channel region is formed between the source and the drain when a bias is applied to the gate electrode. Source drain and body contacts are preferably formed of the same material in a single fabrication step.

Silicon carbide CMOS devices

For the first time, we present the full characteristics of a newer generation 10kV, 340mOmega SiC MOSFET and 10kV, 15A SiC diode chip set and discuss target applications. The 8.1mm x 8.1mm 10kV SiC MOSFET die was measured to have record low specific RDSON of 100mOmega- cm2 at 25deg C, 15A current rating, and only 6.5mJ total switching energy when switched at 6kV, 15A, 150deg C. The accompanying anti-parallel 10kV diode chip has the same die size, a 25% reduction from previous efforts. This new class of 10kV SiC die is targeted for several new applications, including solid state transformers utilizing a 7.2kV or 4.16kV line-voltage.

New Generation 10kV SiC Power MOSFET and Diodes for Industrial Applications

Low Interface State Density Oxides on P-Type SiC

It is well known that SiC can be thermally oxidized to form SiO/sub 2/ layers. And Si MOSFET IC's using thermally grown SiO/sub 2/ gate dielectrics are the predominant IC technology in the world today. However the SiC/SiO/sub 2/ interface has not been well characterized as was the case for Si MOS in the early 1960's. This paper presents data which for the first time characterizes the SiC/SiO/sub 2/ interface and explains one of the previously unexplained abnormalities observed in the characteristics of SiC MOSFET's. >

SiC MOS interface characteristics

This paper reports the design, fabrication and high temperature characteristics of 1 mm/sup 2/, 4 mm/sup 2/ and 9 mm/sup 2/ 4H-SiC p-i-n rectifiers with 6 kV, 5 kV, and 10 kV blocking voltage, respectively. These results were obtained from two lots in an effort to increase the total power levels on such rectifiers. An innovative design utilizing a highly doped p-type epitaxial anode layer and junction termination extension (JTE) were used in order to realize good on-state as well as stable blocking characteristics. For the 1 mm/sup 2/ and 4 mm/sup 2/ rectifier, a forward voltage drop of less than 5 V was observed at 500 A/cm/sup 2/ and the peak reverse recovery current shows a modest 50% increase in the 25/spl deg/C to 225/spl deg/C temperature range. On the 10 kV, 9 mm/sup 2/ rectifier, a forward voltage drop of less than 4.8 V was observed at 100 A/cm/sup 2/ in the entire 25/spl deg/C to 200/spl deg/C temperature range. For this device, the reverse recovery characteristics show a modest 110% increase in the peak reverse recovery current from 25/spl deg/C to 200/spl deg/C. A dramatically low Q/sub rr/ of 3.8 /spl mu/C was obtained at a forward current density of 220 A/cm/sup 2/ at 200/spl deg/C for this ultra high voltage rectifier. These devices show that more than three orders of magnitude reduction in reverse recovery charge is obtained in 4H-SiC rectifiers as compared to comparable Si rectifiers.

John W. Palmour

Papers

Silicon carbide CMOS devices

New Generation 10kV SiC Power MOSFET and Diodes for Industrial Applications

Low Interface State Density Oxides on P-Type SiC

SiC MOS interface characteristics

Large area, ultra-high voltage 4H-SiC p-i-n rectifiers