First-principles study of the compensation mechanism for nitrogen acceptors in ZnSe

We present a mechanism for the compensation of N acceptors in ZnSe through first-principles pseudopotential calculations. In Se-rich conditions, the formation of ${\mathrm{N}}_2$ molecules that are electrically inert neutralizes the acceptor activity, with the maximum acceptor density achievable with N dopants being about ${10}^{18}$ ${\mathrm{cm}}^{\mathrm{-}3}$, in good agreement with experiments. Going to Zn-rich conditions, the hole density is increased by an order of magnitude, suggesting a promising low-resistance p-type doping; however, a self-compensation still occurs due to a [100]-split interstitial N-N complex occupying a Se site, which behaves as a double donor.