(Invited) Materials for Power Electronics – the Role of Defects and Dielectric Passivation
Authors: Heitmann Johannes 
Published: May 2020

SiC and GaN are the main semiconductor materials for current power electronics [1,2]. In this contribution, we will review our efforts to realize a complete chain of material characterization stretching from characterization of point defects, impurities and strain, passivation by thin dielectric films to device fabrication for wide band gap devices. For a better device performance, a detailed understanding of the defects contained in the material and the passivation capability of dielectric layers, hence the formed interface defect states is mandatory. We will show the impact of SiC and GaN defect states on the minority carrier lifetime and their luminescence behavior. Interestingly, we find a stretched exponential decay in the lifetime measurements on free standing 4H-SiC, which hints at a temperature activated carrier migration effect contributing to the near band edge luminescence signal quenching/band-to-band carrier recombination [3]. In addition, the role of different dopant elements on the luminescence behavior of GaN was investigated focusing on transition metal [4,5] and carbon doping [6], which experiences new interest due to potential application for quantum computation [7] and novel electronic properties [8]. In the case of GaN the semiconductor–high-k dielectric interface was investigated in detail and the integration in so called MISHEMT (metal-insulator-semiconductor high electron mobility transistors) with different dielectrics and varying thermal budgets could be shown. Here, the impact of a fully amorphous dielectric (Al2O3), which was kept amorphous by the integration of a low thermal budget ohmic contact [9], was compared to an epitaxial dielectric (GdScO) [10]. By this, a reduction of the trapping behavior of the devices could be shown, achieved by an excellent chemical passivation and a detailed band alignment engineering between dielectric layer and semiconductor material.

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