A generalized method of DC and high-frequency analysis lor microwave transit time diodes in mixed tunnelling and avalanche mode, which can be applied to any type of diode Structure is reported. Taking a purely field-dependent tunnel generation rate for electrons, the same is computed lor holes from a simulated energy band diagram within the depletion layer of the diode. The method has been applied to a variety of Si, GaAs and InP diode structures. The results show a substantial degradation of IMPATT properties due lo phase distortion caused bv the tunnelling current.

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The resJ ts of accurate and realist:c high-frequency numerical analysis of a si.icon DAR (double avalanche region) diode indicate some unique and useful m crowave characteristics. The DAR diode under any structural condition exhibits multioand microwave negative resistance cnaracteristics between 8 and 350 GHz which WoJld make it possible to realize w.de-band microwave oscillations (8 to 350 GHz) from any s:ngle OAR diode witn a mulrituning facility. The negat.ve resistance space distribution profiles of the diode at h:gh frequencies of operation shows near sinusoidal variation, bhich suggests that a OAR diode can have several 0ptimt.m diode widths for generation of a paflicular frequency. The results have been explained on the bas3 of computation of the total avalanche delay produced in both avalanche regions and transit time delay produced in the drift region.

Graphene emerged in 2004 as the first 2-D material with exotic properties. Since then the literature has been flooded with reports, with physicists, material scientists, and engineers grabbing their respective shares. Numerous reviews have also been published. While these reviews have done excellent works in their own ways, new reports are coming up faster than they could draw the attentions of researchers. The authors, therefore, feel that there is a demanding scope for a fresh review. Further, many aspects of graphene are not covered in the reviews so far. New concept devices are also entering into the arena of graphene day by day. The purpose of this paper is therefore to present a comprehensive review on the conventional as well as novel device applications of graphene. While we believe that graphene is the material which will transform the electron devices from the classical regime to the quantum world, it is difficult to believe that it will be a complete substitute to silicon in the near future.INDEX TERMS Graphene, growth process, logic devices, magneto-electronic devices, optoelectronic devices, RF devices.

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