标题: 周期性线状图案a-plane蓝宝石基板成长半极性氮化镓薄膜之研究
Growth of semipolar GaN films on a-plane sapphire substrates with periodic line patterns
作者: 郑文豪
Cheng, Wen-Hao
吴耀铨
Wu, Yew-Chung
材料科学与工程学系
关键字: 蓝宝石基板;氮化镓;半极性(10-11)氮化镓;sapphire substrate;GaN;semi-polar (10-11)GaN
公开日期: 2010
摘要: 一般在蓝宝石基板(a、c-plane sapphire substrate)上成长GaN发光二极体时,都会沿着极性c轴的GaN晶面成长,如此一来便会产生内建电场造成能带扭曲,使得电子电洞复合机率下降,减少内部量子效率,同时也因能带扭曲会有发光波长红移-蓝移的现象,而解决或降低能带扭曲现象的其中一个方法就是使磊晶成长方向沿着非c轴方向成长,也就是非极性或半极性GaN晶面,因此本研究希望制作出a-plane线状图案化蓝宝石基板成长半极性的GaN晶面。

  在第一组实验与平边平行的a-plane线状图案化蓝宝石基板中,利用干蚀刻的方式分别制作出Pyramid-DPSS与Flat-DPSS做比较,发现不管在SEM表面形貌、XRC半高宽、PL发光强度…等等量测都显现出Flat-DPSS具有较好特性,但是XRD鉴定晶面后发现所成长出来的仍为极性GaN晶面,而Pyramid-DPSS则是利用侧壁成功成长出半极性的(10-11)GaN晶面。

   而第二组实验与平边夹三十度的a-plane线状图案化蓝宝石基板中,利用干加湿蚀刻的方式裸露出特定(13-46)sapphire斜面,湿蚀刻同时也改善了受到干蚀刻受损的表面,并且成功在上成长半极性的(10-11)GaN晶面,但该晶面的成长速率仍然偏慢,且表面形貌仍有点粗糙,若未来改善该晶面的成长速率以及表面的平整度,对于后续制作成LED元件时,预估将对发光波长红移-蓝移的现象有很大的改善。
As generally recognized, built-in electric field will emerge along the polar c-axis of GaN epitaxial layers when growing the GaN base LEDs on a-、c-plane sapphire substrates. This may cause distortions of energy band gap, thereby decreases the recombination probability of electron-hole pairs and affects the internal quantum efficiency of such a structure. Moreover, energy band gap distortions will also produce red-blue shift in the emission wavelength. In order to alleviate this built-in electric field, non-polar or semi-polar GaN should be grown on sapphire instead. In this thesis, a-plane line patterned sapphire substrates followed by growth of LED structure are fabricated and non-polar or semi-polar GaN is expected to grow on sapphire substrates.

In the first experiment, the dry etching method is employed to produce both Pyramid-DPSS and Flat-DPSS with line patterns parallel to the flat of sapphire substrates. And the Flat-DPSS is observed to possess better properties in SEM surface morphology、FWHM of XRC and PL intensity…etc. However, it is examined to still be polar c-plane GaN under XRD θ-2θ scan. On the other hand, the semi-polar (10-11)GaN successfully grows on Pyramid-DPSS by its side walls.

  In the second experiment, the a-plane line patterned sapphire substrates with 30° miscut to sapphire flat is fabricated. The semi-polar (10-11)GaN is successfully grown on specific (13-46)sapphire plane exposed by hybrid dry plus wet etching. And the wet etching method can repair the damaged surface caused by dry etching. Nevertheless, problems of growth rate and surface morphology still exist. The red-blue shift issues exist in LED devices manufacture may be resolved if these problems are overcome in the future research.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT079818513
http://hdl.handle.net/11536/47351
显示于类别:Thesis