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

Improved 10-GHz Operation of GaN/AlGaN HEMTs on Silicon Carbide

Large area (8 mm x 7 mm) 1200 V 4H-SiC DMOSFETs with a specific on-resistance as low as 9 m•cm2 (at VGS = 20 V) able to conduct 60 A at a power dissipation of 200 W/cm2 are presented. On-resistance is fairly stable with temperature, increasing from 11.5 m•cm2 (at VGS = 15 V) at 25°C to 14 m•cm2 at 150°C. The DMOSFETs exhibit avalanche breakdown at 1600 V with the gate shorted to the source, although sub-breakdown leakage currents up to 50 A are observed at 1200 V and 200°C due to the threshold voltage lowering with temperature. When switched with a clamped inductive load circuit from 65 A conducting to 750 V blocking, the turn-on and turn-off energies at 150°C were less than 4.5 mJ.

Performance of 60 A, 1200 V 4H-SiC DMOSFETs

DC characteristics of 4H-SiC p-channel IGBTs capable of blocking -12 kV and conducting -0.4 A (-100 A/cm2) at a forward voltage of -5.2 V at 25°C are demonstrated for the first time. A record low differential on-resistance of 14 mW×cm2 was achieved with a gate bias of -20 V indicating a strong conductivity modulation in the p-type drift region. A moderately doped current enhancement layer grown on the lightly doped drift layer effectively reduces the JFET resistance while maintains a high carrier lifetime for conductivity modulation. A hole MOS channel mobility of 12.5 cm2/V-s at -20 V of gate bias was measured with a MOS threshold voltage of -5.8 V. The blocking voltage of -12 kV was achieved by Junction Termination Extension (JTE).

12 kV 4H-SiC p-IGBTs with Record Low Specific On-Resistance

The hole lifetime /spl tau//sub p/ in the n-base of 4H-SiC diodes with 5.5 kV blocking voltage has been measured in the temperature range 300-550 K. The /spl tau//sub p/ increases monotonically in this temperature range from 0.6 to 3.8 /spl mu/s. Forward current-voltage characteristics demonstrate a very high level of base modulation by minority carriers.

High hole lifetime (3.8 [micro sign]s) in 4H-SiC diodes with 5.5 kV blocking voltage

This paper summarizes the recent demonstration of 3200 V, 10 A BJT devices with a high common emitter current gain of 44 in the linear region, and a specific on-resistance of 8.1 mΩ- cm2 (10 A at 0.90 V with a base current of 350 mA and an active area of 0.09 cm2). The onresistance increases to 40 mΩ-cm2 at 350°C, while the DC current gain decreases to 30. A sharp avalanche behavior was observed with a leakage current of 10 μA at a collector voltage of 3.2 kV.

John W. Palmour

Papers

Improved 10-GHz Operation of GaN/AlGaN HEMTs on Silicon Carbide

Performance of 60 A, 1200 V 4H-SiC DMOSFETs

12 kV 4H-SiC p-IGBTs with Record Low Specific On-Resistance

High hole lifetime (3.8 [micro sign]s) in 4H-SiC diodes with 5.5 kV blocking voltage

High Temperature Characterization of 4H-SiC Bipolar Junction Transistors