Wide Band Gap Semiconductor Based Highpower ATT Diodes In The MM-wave and THz Regime: Device Reliability, Experimental Feasibility and Photo-sensitivity

that when an electron bunch from a forward biased cathode is injected into the depletion layer of a reversed biased p-n junction a ‘transit time negative resistance’ is produced as the electrons drift across the high field region. The negative resistance from such early devices was found to be small and microwave power output was low. Read showed that an improved negative resistance is obtained when impact ionization is used to inject the electrons. He showed that the properties of charge carriers in a semiconductor i.e. (i) avalanche multiplication by impact ionization and (ii) transit time delay of charge carriers due to saturation of drift velocity at high electric fields, could be suitably combined in a reverse-biased p-n junction to produce a microwave negative resistance. By exploiting the time delay required to build up an avalanche discharge by impact ionization, coupled with Shockley’s transit time delay, he showed that efficient microwave oscillation could be realized in his proposed p + n i n + diode. However, due to the complicated nature of the Read structure, it was not until 1965 that the first experimental Read diode was fabricated. In the early 1965 Johnston et al. , from Bell Laboratories, first made a successful experimental observation of microwave oscillations from a simple Si p-n junction diode. This study showed that the complicated Read structure was not essential required for generating microwave oscillations. On the basis of a small-signal analysis, T. Misawa showed that negative resistance would occur in a reverse biased p-n junction of any arbitrary doping profile. Since then, rapid advances have been made towards further development of various IMPATT structures, fabrication techniques as well as optimum circuit design for IMPATT oscillators and amplifiers. The frequency range of IMPATT devices can be pushed easily to MM and sub-MM wave ranges at which comparable amount of RF power generation is hardly possible by other two-terminal solid-state devices. is no well defined avalanche region at the frequencies where efficiencies falls off. However, the study confirms the efficiency and power advantages of MM-Wave SiC IMPATT oscillators. Later, Zhao [ Zhao et al. (2000)] have reported the Monte Carlo Particle simulation of 4H-SiC based hi-lo SDR IMPATT diode at 200 GHz. A low voltage (Vdc = 74 V) 4H-SiC IMPATT diode was designed by them to offer an efficiency of 10% at around 200 GHz with a peak output power of 11 W. This book is planned to publish with an objective to provide a state-of-the-art reference book in the areas of advanced microwave, MM-Wave and THz devices, antennas and systemtechnologies for microwave communication engineers, Scientists and post-graduate students of electrical and electronics engineering, applied physicists. This reference book is a collection of 30 Chapters characterized in 3 parts: Advanced Microwave and MM-wave devices, integrated microwave and MM-wave circuits and Antennas and advanced microwave computer techniques, focusing on simulation, theories and applications. This book provides a comprehensive overview of the components and devices used in microwave and MM-Wave circuits, including microwave transmission lines, resonators, filters, ferrite devices, solid state devices, transistor oscillators and amplifiers, directional couplers, microstripeline components, microwave detectors, mixers, converters and harmonic generators, and microwave solid-state switches, phase shifters and attenuators. Several applications area also discusses here, like consumer, industrial, biomedical, and chemical applications of microwave technology. It also covers microwave instrumentation and measurement, thermodynamics, and applications in navigation and radio communication.