Studies on Electrical Characteristics and optical tuning properties of semiconductor superlattice type avalanche transit time devices operating as Room temperature Terahertz Sources

Abstract

The non-availability of potential high power generating devices in the field of so-called tera-gap, which is recognized as (0.1-10)THz, has opened a broad spectrum of research-activity. With ever-increasing demand of high-frequency usage, mainly dedicated to serve communication as well as defence purpose, the proportional power production has become a challenge in the technical domain, owing to different constraints where the integrable device size and performance limitation are two major issues. Up till now, several research works have been conducted in different corners of the World to propose power-generating devices, that may have suitability in the frequency range below or above the tera-gap, i.e., in the conventional electronics as well as photonics domain. Various devices, like MESFETs as well as Quantum-Cascade-Oscillators have been developed, which have shown their prospective outcome in the frequency bands, either below 100GHz or above 1THz. But, no such large-scale device operations in either theoretical or experimental way, dedicated to serve the particular frequency spectrum, in between these two extremes have been reported yet. Avalanche-Transit-Time (ATT) devices have become a de-facto standard for a couple of decades or more than that to leverage the terahertz effect, which includes rapidly increasing communication systems with wide bandwidth, biomedical as well as defence service. The high power generating possibility have been established in ATT devices at sufficiently high frequency domain. newlineThe effect of mixed tunnelling and avalanche-mechanism on high frequency power generation has been extensively worked out in this research. This thesis, for the first time, includes mainly the thorough investigation of high-power generation possibility from wide band-gap heterostructure materials at tera-hertz spectrum, by means of uniquely developed and experimentally verified non-linear mixed-quantum-drift-diffusion simulator. Mainly Si/SiC, GaN/AlGaN material based ATT device studies on large-signal pow