梯度组分缓冲层诱导的单一立方相Mg_(0.3)Zn_(0.7)O薄膜外延生长

Controlled Growth of Pure Cubic Mg_(0.3)Zn_(0.7)O Thin Films on c-plane Sapphire by Introducing Graded Buffer Layer

为了实现MgZnO合金带隙全跨度调制,利用低压MOCVD设备,在c面蓝宝石衬底上采用MgO籽晶层和组分渐变缓冲层控制立方相MgxZn1-xO薄膜的生长,获得了Zn组分达到0.7的单一立方相MgxZn1-xO薄膜,把MgZnO合金带隙调制范围从MgO一侧扩展到了4.45 eV,覆盖了整个日盲紫外波段。对比实验分析表明,这种高Zn组分立方相MgZnO薄膜的生长得益于缓冲层晶格模板的结构诱导作用和适宜的生长温度(350~400℃)。Mg0.3Zn0.7O基MSM结构紫外探测器响应峰位于270 nm,截止波长295 nm。

Developing growth techniques to suppress phase separation is a key point to realize bandgap modulation of MgZnO from 3. 3 to 7. 8 eV. A graded quasi-homo buffer layer,composed of a MgO layer and a continuously Zn-increased MgZnO layer,was used to grow pure cubic MgxZn1- xO thin films on c-plane sapphire by MOCVD method. The Zn content in rocksalt MgxZn1- xO is expanded to ~ 0. 7 and the optical bandgap of the films was decreased as low as 4. 45 eV,corresponding to the long wavelength edge of solar-blind band. Parallel experiments suggested that the buffer layer played an important role as a structural template for the following growth of Mg0. 3Zn0. 7O epilayers and a substrate temperature range from 350 ℃ to 400 ℃ was benefit to increase solution of Zn in the RS-MgZnO films. A photoconductive UV detector based on a Mg0. 3Zn0. 7O film exhibits responsivity peak at 270 nm and a cutoff wavelength at 295 nm.