EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Interfaces govern the behaviour of all electronic devices. Herbert Kroemer coined the famous phrase “the interface is the device” in his 2000 Nobel Prize lecture, and we are still applying tremendous effort to understand interfaces in new material generations, with wide-bandgap materials being no exception. If anything, wide bandgap materials are more vulnerable to defect states purely due to their larger bandgap. Understanding of the bulk behaviour of semiconductors can often not be extended to their behaviour in structured film stacks were interfaces play a vital role. SiC/SiO₂ is a prototypical wide-bandgap semiconductor/dielectric interface. A multitude of different defects leads to unacceptably large defect densities in the vicinity of the conduction band of 4H-SiC. The management of interfacial defects remains a topic of lively discussion and current interest.

Here, we present a systematic study of the 4H-SiC/SiO₂ interface in industrially manufactured samples with a particular focus on the effects of nitridation in N₂, NO, NH₃ and NO+NH₃ atmospheres. High temperature nitridation has been shown to compensate interface defects leading to an increase in device performance, however, information on the local chemistry at the interface after such processes is scarce, limiting the understanding of the interface and consequently the targeted improvement of device characteristics. The present work uses energy-dependent hard X-ray photoelectron spectroscopy (HAXPES) to systematically study the elemental distributions and chemical environments across the 4H-SiC/SiO₂ interface. We combine both laboratory- and synchrotron-based HAXPES results to obtain a complete picture of this important technological interface and to benchmark the capabilities of this spectroscopic technique for the exploration of buried interfaces in device heterostructures in general.