Electronic characterization of technologically relevant interfaces on beta Gallium Oxide and 4H-SiC wide bandgap semiconductors

Abstract

Conventional silicon power device technologies are rapidly approaching their performance limits in power devices. Therefore, exploration of novel materials for next-generation power electronics is necessary. In this regard, wide bandgap (WBG) semiconductors are an ideal solution. The excellent material properties as well as availability of the single crystal material attracts more attention towards 4H-SiC and beta Gallium Oxide. Specially, for power electronics, WBG Schottky diodes and metal oxide field effect transistors (MOSFETs) are attractive for high voltage applications due to lower power/energy loses. In such devices, metal-semiconductor interfaces (Schottky diodes) and dielectric-semiconductor interface (MOSFETs) play a critical role in the physics of device operation. However, various non-idealities and defects that are present at such interfaces as well as defects present in the bulk of the semiconductors affect power device performance and reliability. Bulk defects in the semiconductor cause recombination current under reverse bias, increase substrate resistivity and affect in degradation of voltage blocking capability of the power device. On the other hand, interface defects such as high density of interface traps (Dit) in oxide semiconductor interface known to be the reason for very low channel mobility in MOSFETs. Furthermore, surface roughness at the interface, surface contamination at the interface and as well as a reaction at the interface can also affect the power device performance. Therefore, electronic characterization of interfaces on 4H-SiC and beta Gallium Oxide is a fundamental step in the development of power devices based on these materials. Furthermore, power device fabrication requires several processing steps such as metallization, dielectric formation, and reactive ion etching. These unit steps introduce new or altered metal-semiconductor interfaces or oxidesemiconductor interfaces as well as semiconductor surface. Therefore, it is essential to fully understand the nature of the various defects introduced by these unit steps. In this thesis, electronic characterization of metal-semiconductor, dielectric-semiconductor interface as well as bulk defect investigation has been carried out to identify the defect structures as well as their behavior.