Fabrication and structural, electrical characterization of i-ZnO/n-ZnO nanorod homojunctions

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• 作者：S. Y谋lmaz^a ; ^b ; ^{s_yilmaz@ktu.edu.tr} ; ^{slh_yilmaz@yahoo.com.tr} ; E. Bacaks谋z^a ; 陌. Polat^a ; Y. Atasoy^a
• 关键词：i&ndash ; n ZnO homojunction ; (Na&ndash ; Mg) co-doping ; SEM ; XRD ; Temperature dependence of I&ndash ; V characteristics
• 刊名：Current Applied Physics
• 出版年：2012
• 期刊代码：15_15671739
• 类别：ph
• 出版时间：September, 2012
• 卷：12
• 期：5
• 页码：1326-1333
• 文件大小：700 K

摘要

Well-aligned ZnO nanorods were synthesized by a vapor phase transport method on ZnO buffer layer coated n-Si substrates. X-ray diffraction and scanning electron microscopy results showed that the deposited ZnO nanorods crystallize in the wurtzite structure and are highly textured with their c-axes normal to the substrate and show a clearly hexagonal morphology. A heavily compensated and intrinsic ZnO layer (i-ZnO) doped with both Mg and Na was deposited on the nominally undoped ZnO nanorods (which show a natural n-type behavior) to produce an i-ZnO/n-ZnO homojunction. The i-ZnO layer consisted of the grainy shape nano-crystallites with the wavy surface morphology. The current-voltage (I-V) characteristics of these structures in the temperature range of 150-300聽K have been analyzed in the framework of standard thermionic emission (TE) theory with the assumption of a Gaussian distribution of the barrier heights. The values of zero bias barrier height (桅_b0) and ideality factor (n) were found to be strongly temperature dependent whereby n decreases while 桅_b0 increases with increasing temperature. The ln(I₀/T²) vs q/kT plot shows a straight line behavior and the values of activation energy (E_a聽=聽桅_b0) and the Richardson constant (A*) determined from the intercept and slope of the plot were 0.926聽eV and 2.61聽脳聽10^鈭?聽A聽cm^鈭?聽K^鈭?, respectively. This value of A* is much lower than the known value of 32聽A聽cm^鈭?聽K^鈭? for ZnO. Thus, a modified vs. q/kT plot based on a Gaussian distribution of barrier heights was used which yields a mean barrier height and modified effective Richardson (A**) of 1.032聽eV and 34.85聽A聽cm^鈭?聽K^鈭?, respectively. This value of A** is much closer to the theoretical value of 32聽A聽cm^鈭?聽K^鈭? for ZnO.