重掺杂AZO透明导电薄膜的光电特性

Optical and Electrical Properties of Heavy-doped AZO Transparent Conducting Thin Films

以Al质量分数为2%的ZnO陶瓷靶为靶材,在氧气气氛中,采用脉冲激光沉积方法(PLD)在石英衬底表面生长了重掺杂的ZnO∶Al(AZO)薄膜。通过X射线衍射仪、紫外可见分光光度计、微区拉曼光谱仪、霍尔测量仪对合成薄膜材料的晶体结构、光学、电学性质等进行了研究。结果表明:所制备的AZO薄膜呈现具有高度c轴择优取向的ZnO纤锌矿结构;重掺杂下的AZO显示了简并半导体的性质,电学呈现出了类金属特性;在可见光区域透过率>80%,吸收边和紫外发光峰出现了明显的蓝移现象,被归结为重掺杂下引起的Burstein-Moss效应导致光学带隙展宽。

Al-doped ZnO（AZO） film have been actively investigated for potential applications in solar cells,flat panel displays,transparent heat mirrors and organic light emitting diodes,etc.,because of high transmittance in the visible region,low resistance and better stability.Extensive work has been concentrated on the fabrication and characterization of AZO thin films.All results show that the average transmittance of the visible light is above 80%,the resistivity can be changed from values as low as 10-4 Ω·cm to values as high as 104 Ω·cm.However,a few researches are devoted to the optical and electrical properties in heavy Al doping AZO thin films.In particular,there are hardly any reports regarding the conductivity mechanism of heavily doped AZO thin films.In this paper,AZO thin films with heavy Al doping concentration were grown on quartz（SiO2） substrates by pulsed laser deposition（PLD） method.ZnO mixed with Al2O3（mass fraction is 2%） was used as target.The structure,optical and electrical properties of AZO thin films were investigated by using X-ray diffraction（XRD）,transmission spectra,photoluminescence（PL） spectra and Hall effect measurement.XRD patterns indicate that all AZO thin films have the wurtzite structure of ZnO with a strong c-axis preferred orientation.The electrical measurement of AZO thin films show a good conductivity.The highest carrier density and the Hall mobility are 9.01×1020 cm-3 and 33 cm2·V-1·s-1,respectively.The conducting mechanism was studied by temperature-dependent Hall-effect measurement.The temperature variation of carrier concentration from shows alike-metallic conducting behavior.All AZO thin films have good optical quality.The optical transmittance is above 80%,the highest transmittance is about 90%.The PL spectrum in AZO thin films is dominated by near band edge（NBE） emission at room temperature.The absorption edge and NBE emission peak of AZO thin films show an obvious blueshift by comparing the undoped ZnO films,and this blueshift is proportional to Al-doping concentration.The above result can be explained by band gap widening due to Burstein-Moss effect.