Abstract
Group IV donors in ZnO are poorly understood, despite evidence that they are effective n-type
dopants. Here we present high-resolution photoluminescence (PL) spectroscopy studies of
unintentionally doped and Sn-doped ZnO single crystals grown by the chemical vapor transport
method. Doped samples showed greatly increased emission from the I10 bound exciton transition
that was recently proven to be related to the incorporation of Sn impurities based on radioisotope
studies. The PL linewidths are exceptionally sharp for these samples, enabling a clear
identification of several donor species. Temperature-dependent PL measurements of the I10 line
emission energy and intensity dependence reveal a behavior that is similar to other shallow
donors in ZnO. Ionized donor bound-exciton and two-electron satellite transitions of the I10
transition are unambiguously identified and yield a donor binding energy of 71 meV. In contrast
to recent reports of Ge-related donors in ZnO, the spectroscopic binding energy for the Snrelated
donor bound exciton follows a linear relationship with donor binding energy (Haynes
rule) similar to recently observed carbon related donors, and confirming the shallow nature of
this defect center, which was recently attributed to a SnZn double donor compensated by an
unknown single acceptor.