利用脈衝雷射鍍膜製備ZnO/Si異質接面之電特性研究

Electrical Characterization of ZnO/Si Heterojunctions Grown by Pulsed Laser Deposition

余昌峰 ； 許廷維 ； 余諮宜

《國家奈米元件實驗室奈米通訊》 15卷4期 (2008/12) Pp. 26-30

https://doi.org/10.29913/NDLC.200812.0006

摘要

利用脈衝雷射蒸鍍法(Pulsed Laser Deposition, PLD)法在玻璃基板鍍上不同摻雜比例之氧化鋅鋁(Aluminum Zinc Oxide, AZO)薄膜，X光繞射儀顯示AZO薄膜具有沿c軸(002)的優先取向。電性部分，鋁摻雜使薄膜載子濃度增加，導電度大幅改善，在摻雜20%時，可得到最低電阻率1.401×10^(-3)Ω-cm。光學量測中發現薄膜在可見光波段的穿透度可達85%~90%，且能隙會隨著載子濃度增加而增加。
另一方面，利用PLD在p型矽晶圓上鍍氧化鋅鋁AZO薄膜組成異質結構pn二極體，並對該結構進行I-V和C-V特性分析，由logl-V曲線可發現當施予順向偏壓之異質結構在偏壓較大時，異質結構產生與溫度無關的穿隧電流；而在C^(-2)-V曲線中發現異質結構操作環境越低溫，曲線越接近理想狀態，且隨著溫度升高，能障高度值亦增大，推測此現象受異質結構中的界面態電荷影響。此外，在對不同摻雜之AZO薄膜與p-Si異質結構中的研究中，25% AZO薄膜具有最高能障和最大切入電壓，1.6%次之，20%最小。

關鍵字

脈衝雷射鍍膜 ； 氣化鋅 ； pn異質接面 ； 能障

並列摘要

Pulsed laser deposition (PLD) technique is used to deposit Al-doped ZnO (AZO) thin films on glass substrates. XRD studies indicated that the obtained AZO thin films were hexagonal wurtzite type structure with strong (002) c-axis orientation with various Al-doped concentration. The resistivity of the AZO thin film decreased rapidly with the increase of Al-dopant to a minimum of 1.401×10^(-3) Ω-cm at 2% Al-dopant. All thin films show over 85% optical transmission in the visible range. The energy band gap of AZO thin films increases with the increase of carrier concentration.
AZO films were prepared by PLD process on p-type (100) Si substrates to fabricate AZO/p-Si heterojunctions. The electrical transport properties of the AZO/p-Si heterojunctions were investigated by temperature-dependent current-voltage (I-V) measurements and capacitance-voltage (C-V) measurements. The temperature-dependent log I-V characteristics revealed that the forward currents can be classified into two regions according to the applied voltages. In high forward bias region, the plots of log I-V of AZO/p-Si hetrojunctions are independent of the measurement temperatures. The current is dominated by a tunneling mechanism.
The AZO/p-Si heterojucntion can fit with the typical C-2-V relationship at the lower measurement temperature. It may be due to the interface charge of the heterojunction structure can be suppressed at lower temperature. The potential barrier height can be estimated from the extrapolated intercept of C-2 with the voltage axis. The potential barrier height of 2.5% Al dopant is higher than the 1.6 and 2.0% Al dopant.