As-doped p-type ZnO produced by an evaporation∕sputtering process

Abstract

Strongly $p$ -type ZnO is produced by the following sequence of steps: (1) evaporation of ${\mathrm{Zn}}_3{\mathrm{As}}_2$ on a fused-quartz substrate at $350°\mathrm{C}$ ; and (2) sputtering of ZnO with substrate held at $450°\mathrm{C}$ . The electrical characteristics include: resistivity of $0.4\Omega \mathrm{cm}$ , a mobility of $4{\mathrm{cm}}^2∕\mathrm{V}\mathrm{s}$ , and a hole concentration of about $4\times {10}^{18}{\mathrm{cm}}^{-3}$ . This resistivity is among the best (lowest) ever reported for $p$ -type ZnO. Secondary-ion mass spectroscopic analysis gives an average As concentration about $5\times {10}^{19}{\mathrm{cm}}^{-3}$ , and a simple one-band fit of the temperature-dependent mobility curve yields an acceptor concentration of about $9\times {10}^{19}{\mathrm{cm}}^{-3}$ . This is strong evidence that the $p$ -type dopant involves As, although it is not clear whether the acceptor is simply ${\mathrm{As}}_{\mathrm{O}}$ or the recently suggested ${\mathrm{As}}_{\mathrm{Zn}}-2{\mathrm{V}}_{\mathrm{Zn}}$ .