Suppressing the carrier concentration of zinc tin nitride thin films by excess zinc content and low temperature growth

We report the electrical properties of zinc tin nitride (Zn1+xSn1-xN2) thin films grown by reactive sputtering in an ultrahigh vacuum chamber. It is demonstrated that both the Zn-rich content and low-temperature growth are beneficial for suppressing the carrier concentration. Nondegenerate thin films with a composition of Zn/(Zn+Sn) = 0.72 show the carrier concentration of 2.7 × 1017 cm−3 at 300 K and the activation energy of 0.14 eV, which are in contrast to previously formed degenerate thin films with a much higher carrier concentration. Such electrical properties are consistent with the recent first-principles calculation, suggesting that excess Zn can reduce the amount of native donor-type Sn-on-Zn (SnZn2+) defects, while low-temperature growth can decrease the concentrations of unintentional donor-type oxygen-on-nitrogen (ON+) and/or hydrogen interstitial (Hi+) impurities. These results could provide a general framework for controlling the carrier concentration in II-IV-nitride semiconductors.