Magnetic State around Cation Vacancies in II–VI Semiconductors

The magnetic properties of neutral cation vacancies in II–VI semiconductors are examined using first principles calculations and group theory. A molecular cluster model of a single vacancy in II–VI semiconductors is developed to explain the observed chemical trend. We show that a single Zn vacancy in ZnO yields a total spin $S_T=1$ in agreement with experiments. But for the other less ionic Zn-based II–VI semiconductors $\mathrm{Zn}A$ ($A=\mathrm{S}$, Se, Te) this spin triplet state is nearly degenerate with a nonmagnetic spin singlet state.

Figure 1

Molecular cluster model of the vacancy. The anion and the vacancy are represented by a full and an open circle, respectively, the anion $s{p}^3$ hybridization dangling bonds ${\psi }_i$ are represented in gray (green).

Figure 2

Hole multiplet splitting for cation vacancy.

Figure 3

First low-lying states versus the exchange integral $J$ for anion (left) and cation (right) vacancy. The other parameters are fixed to realistic values: $\Delta =4\mathrm{eV}$ (right) or $-4\mathrm{eV}$ (left), $U=4\mathrm{eV}$, $V=1\mathrm{eV}$.