Assessing the effect of hydrogen on the electronic properties of 4H-SiC

As a common impurity in 4H silicon carbide (4H-SiC), hydrogen (H) may play a role in tuning the electronic properties of 4H-SiC. In this work, we systemically explore the effect of H on the electronic properties of both n-type and p-type 4H-SiC. The passivation of H on intrinsic defects such as carbon vacancies (V_C) and silicon vacancies (V_Si) in 4H-SiC is also evaluated. We find that interstitial H at the bonding center of the Si-C bond (H_i^bc) and interstitial H at the tetrahedral center of Si (H_i^Si-te) dominate the defect configurations of H in p-type and n-type 4H-SiC, respectively. In n-type 4H-SiC, the compensation of H_i^Si-te is found to pin the Fermi energy and hinder the increase of the electron concentration for highly N-doped 4H-SiC. The compensation of H_i^bc is negligible compared to that of V_C on the p-type doping of Al-doped 4H-SiC. We further examine whether H can passivate V_C and improve the carrier lifetime in 4H-SiC. It turns out that nonequilibrium passivation of V_C by H is effective to eliminate the defect states of V_C, which enhances the carrier lifetime of moderately doped 4H-SiC. Regarding the quantum-qubit applications of 4H-SiC, we find that H can readily passivate V_Si during the creation of V_Si centers. Thermal annealing is needed to decompose the resulting V_Si-nH (n=1-4) complexes and promote the uniformity of the photoluminescence of V_Si arrays in 4H-SiC. The current work may inspire the impurity engineering of H in 4H-SiC.