Nontrigonal Ge dangling bond interface defect in condensation-grown(100)Si1−xGex/SiO2

Multifrequency electron-spin-resonance (ESR) study has revealed a nontrigonal Ge dangling bond (DB)-type interface defect in ${\text{SiO}}_2/\left(100\right){\text{Ge}}_x{\text{Si}}_{1-x}/{\text{SiO}}_2/\text{Si}$ heterostructures grown by the condensation method. The center, exhibiting monoclinic-I $\left(C_{2v}\right)$ symmetry, with principal $g$ values $g_1=2.0338\pm 0.0003$, $g_2=2.0386\pm 0.0006$, and $g_3=2.0054$ and lowest $g$ value (DB) direction $24\pm 2°$ off a $⟨111⟩$ direction toward the [100] interface normal, is observed in maximum densities for $x\sim 0.7$, the signal disappearing for $x\le 0.45$ and $x\ge 0.93$. Neither $\text{Si}{P}_b$ type nor trigonal Ge dangling bond defects is observed, enabling unobscured spectral analysis. Based on its ESR parameters, including $g$ matrix and symmetry, it is suggested to concern a $\text{Ge}{P}_{b1}$-type center, that is, not a trigonal basic $\text{Ge}{P}_{b\left(0\right)}$-type center $\left({\text{Ge}}_3\equiv {\text{Ge}}^{•}\right)$, thus exposing a unique interface mismatch healing as function of substrate Ge fraction. Its properties are discussed within the context of the thus far elusive role of interfacial Ge DB defects in Ge insulator structures, encompassing theoretical inferences.