Shallow Donor Ionization Energy in Sn-Doped ZnO Nanobelts

摘要

Donor states of Sn dopants and electronic structures in Sn-doped ZnO nanobelts have been investigated by combining temperature-dependent photoluminescence (PL) and first-principles calculations. The strong and dominant donor-bound exciton ((DX)-X-0) emission was observed in low-temperature PL spectrum of Sn-doped ZnO nanobelts. The (DX)-X-0 emission has thermal activation energy of similar to 12 meV and the corresponding ionization energy was determined to be similar to 60 meV, which is derived from shallow donor nature of Sn dopants. In addition, the (DX)-X-0 peak dissociates into a neural-donor-like defect-pair complex and band-to-band transition with increasing temperature. As a result, the near-band-edge emission peak at room temperature is ascribed to a mixture of band-to-band and free-to-bound transition. Furthermore, first-principles electronic structure calculations indicate that Sn substituting Zn site in ZnO is a rather shallow donor, in good agreement with the PL results.