Publications

Abstract : The rapid development of the power electronic devices over the last few decades to cater demands of ever increasing wireless communication technologies, traditional as well as new military applications, and many more, have been further fueled by work-from-home (WFH) due to unprecedented global pandemic COVID-19. These high frequencies and high-power applications have necessitated the introduction and development of wide bandgap semiconductors over the period because of their suitable material properties. However, these wide bandgap materials, such as silicon carbide (SiC) and gallium nitride (GaN), based device technologies have already extended their cycle of development and optimization due to various reasons. Moreover, still facing critical challenges like producing large-size, cost-effective, and high-quality substrates. In the quest of better material properties suitable for high-voltage and high-frequency applications, a new ultra-wide bandgap (UWB) semiconductor material gallium oxide (Ga2O3), although studied and reported way back in mid of twentieth century, has attracted research community only in last few years as a supplement to existing silicon carbide (SiC) and gallium nitride (GaN) technologies. Ga2O3 is an ultra-wide bandgap (UWB) semiconductor having different crystal structures with energy bandgap values up to 5.3 eV, and bulk crystals can be grown using melt-growth techniques which facilitate the availability of large-size, cost-effective, single-crystal substrates. Gallium oxide crystallizes into five different structures: monoclinic, rhombohedral, defective spinel, cubic, and orthorhombic structures, and represented as β-, α-, γ-, δ-, and ε-Ga2O3, respectively. Among these Ga2O3 polymorphs, β-Ga2O3 is most thermally stable and widely studied as well as reported. Apart from an edge on high-quality native-substrate over existing GaN technology, β-Ga2O3 offers other promising features relating to power device applications, such as large bandgap of 4.9 eV and critical electric field up to 8 MV/cm. This high critical electric field enables significant improvement in the performance of the β-Ga2O3 based high-voltage Schottky rectifiers and enhancement mode (e-mode) metal–oxide–semiconductor field-effect transistors (MOSFETs) over SiC and GaN power devices. Nonetheless, β-Ga2O3 also faces some issues such as relatively low electron mobility that limits DC and on-state performance, the high thermal resistance of the material requires device level thermal management and absence of p-type doping restricts device structure types. In this chapter the overview of state-of-the-art β-Ga2O3 technologies as a supplement to existing SiC or GaN counterparts with a perspective on the growth and development of β-Ga2O3 heterostructure is presented. The device design, microwave, and millimeter-wave (mmW) performance as well as challenges are also presented.