In was implanted into bulk ZnO creating a square profile with a thickness of about 100 nm and an In concentration of about 1×1020 cm-3. The layer was analyzed with Rutherford backscattering, temperature-dependent Hall effect, and low-temperature photoluminescence measurements. The implantation created a nearly degenerate carrier concentration n of about 2×1019 cm-3, but with a very low mobility μ, increasing from about 0.06 cm2/V s at 20 K to about 2 cm2/V s at 300 K. However, after annealing at 600 °C for 30 min, n increased to about 5×1019 cm-3, independent of temperature, and μ increased to about 38 cm2/V s, almost independent of temperature. Also, before the anneal, no excitons bound to neutral In donors, called I9 in literature, were observed in the photoluminescence spectrum; however, after the anneal, the I9 line at 3.3568 eV was by far the dominant feature. Analysis of the Hall-effect data with a parametrized, two-layer model showed that the conduction before the anneal was mainly due to very high concentrations of native donors and acceptors, produced by the implantation, whereas the conduction after the anneal was due to In ions that were nearly 100% activated. These results show that strongly degenerate conductive layers with designed profiles can be created in ZnO with implantation and relatively low-temperature anneals.
Look, D. C.,
Farlow, G. C.,
Vanamurthy, L. H.,
& Huang, M.
(2009). In-Implanted ZnO: Controlled Degenerate Surface Layer. Journal of Vacuum Science & Technology B, 27 (3), 1593-1596.