Formation of germanium oxide microcrystals on the surface of Te-implanted Ge

The formation of voids on the surface of heavily implanted germanium has been known for more than 30 years. Recently there is a renewed interest in germanium due to its potential application in the complementary metal oxide semiconductor (CMOS) devices. Here we report the observation of germanium oxide microcrystals formed on the surface of tellurium implanted into a germanium substrate. The Ge target used was a (1 0 0) polished single crystalline germanium wafer and the implantation was carried out at room temperature with Te ions at 180 keV and a fluence of 3.6 × 1015 at/cm2. Under scanning electron microscope (SEM), the surface of the Ge substrate is evenly covered by microcrystals with a diameter about 1-2 μm and a coverage density of ∼107 particles/cm2. The initially smooth surface of the polished germanium substrate becomes very rough and mostly consists of voids with an average diameter of 40-60 nm, which is consistent with reports of heavily implanted germanium. The composition of the microcrystals was studied using energy dispersive X-ray analysis (EDX) and atom probe tomography (APT) and will be presented. Preliminary results indicate that tellurium is not detected in the microcrystals. The origin of the microcrystals will be discussed.