Effect of O/Zn Flux Ratio on Crystalline Quality of ZnO Films Grown by Plasma-Assisted Molecular Beam Epitaxy

概要

論文の詳細を見る
The effect of O/Zn flux ratio on the crystalline quality of ZnO films grown at 700°C by plasma-assisted molecular beam epitaxy was investigated. Zinc beam flux ($F_{\text{Zn}}$) was varied from $2.2\leq F_{\text{Zn}}\leq 8.3$ Å/s with an O2 flow rate of 3 sccm and RF power of 300 W. The surface morphology of the ZnO layers strongly depended on $F_{\text{Zn}}$. ZnO epilayers grown under stoichiometric flux conditions (i.e., $F_{\text{Zn}}=5.1$ Å/s) had high crystalline quality, as was confirmed by using X-ray diffraction, photoluminescence (PL), and Hall-effect measurements: the full width at half maximum (FWHM) of a skew symmetric ($10\bar{1}0$) X-ray rocking curve was 720 arcsec; the dominant neutral donor bound exciton emission intensity in the PL spectra became maximum with the narrowest FWHM; the electron mobility was a maximum of 130 cm2V-1s-1; and a residual carrier concentration of $1.2\times 10^{17}$ cm-3 was achieved. We demonstrated that stoichiometric ZnO films have the lowest dislocation density and the highest electron mobility compared with ZnO films grown under nonstoichiometric flux conditions.
2003-04-15