利用脈衝雷射分子束磊晶之氧化鋅薄膜的成長與光學特性研究

Abstract

我們利用雷射分子束磊晶的方法，雷射光源為KrF準分子雷射，波長248nm。成功的在c切面的氧化鋁基板上成長出具有高度c軸取向的氧化鋅薄膜，在最佳條件下氧化鋅(002)面的XRD半高寬為0.06度。在原子力顯微鏡的分析中，幾乎所有的氧化鋅薄膜都有良好的表面粗慥度。在低溫下的螢光光譜量測中，被中性施主束縛住的激子輻射強度大於其它的光譜；並且當環境溫度增加時，自由激子的輻射強度會漸漸的增加，最後在室溫下其強度為最強。從室溫穿透光譜量測中，在最佳濺鍍條件下的氧化鋅薄膜的能隙值和氧化鋅靶材的值相似，並在可見光的穿透率皆超過90%。從反射式高能量電子繞射圖得知，氧化鋅的磊晶是旋轉30度後再成長在基板上的；從霍爾量測得到的薄膜的電子漂移率是27 cm2/V•sec，N型的載子濃度為1 ×1017 cm—3.

We have successfully fabricated highly oriented (002) ZnO film which has a minimum FWHM of 0.06o in the optimum conditions on c-cut sapphire (0001) by laser-MBE using KrF-excimer laser with a wavelength of 248 nm. Almost all of the films showed low surface roughness from AFM measurement. At low temperature PL, the neutral-donor bound exciton emission dominates the spectra and the FWHM is 4meV , while with increasing temperature, free exciton emissions grow rapidly and finally become the dominant lines. From the transmittance measurement, the bandgap value of the as-deposited ZnO film for the optimum condition was similar to that of 3.37 eV for the ZnO bulk. And the transmittance data was shown to be higher than 90% in the visible region. From the RHEED pattern, we found that the 30o rotation of the crystal orientation of the ZnO epilayer against the substrate occurs. From the Hall measurement, the mobility is 27 cm2/V•sec and the concentration is 1 ×1017 cm—3 after in-situ annealing.