Method for growing aln template for epitaxy on sapphire substrate

Abstract

Provided is a method for growing an epitaxy AlN template on a sapphire substrate. According to the scheme, trimethylaluminum is used as an MO source, NH3 is used as a gaseous source, and a metal organic chemical vapor deposition process is used for growing the AlN template on the surface of a sapphire; when the AlN template is grown, the trimethylaluminum is connected into a reaction chamber before the NH3, 1-5 seconds are delayed before the NH3 is connected into the reaction chamber after the trimethylaluminum is connected in, the NH3 is reacted with Al atoms which are attached to the surface of the sapphire so that AlN can be generated, and the AlN template is finally grown on the surface of the sapphire. The V / III ratio of the NH3 and the trimethylaluminum is 51-256, the air pressure of the reaction chamber is 20-50mbar, and the temperature in the reaction chamber is 1200 DEG C. The method for growing the epitaxy AlN template on the sapphire substrate has the advantages that the method is simple and practical, a buffering layer is of no need, the AlN template with the atomic smooth surface can be grown under the relatively low substrate temperature of (1200 DEG C), and the mean roughness of the AlN template is about 0.5nm.

Description

technical field [0001] 本发明涉及一种有机物化学汽相沉积(MOCVD)工艺,尤其涉及一种在蓝宝石衬底上生长外延用AlN模板的方法。 Background technique [0002] 目前,国内外以蓝宝石 / GaN为基底的氮化物外延生长技术已经非常成熟,但是对于深紫外光电子器件而言,由于GaN材料对紫外光的强烈吸收作用将导致器件发光效率的严重降低,几乎所有的入射光都会被GaN层吸收而无法进入有源区产生光电流,因此以蓝宝石 / GaN为基底的氮化物模板不适宜用来制作深紫外光电子器件;为了解决前述问题,一种较为可行的技术路线是:屏弃GaN模板,直接在对深紫外光有良好透过特性的蓝宝石衬底上生长高Al组分的AlGaN外延层。 [0003] 生长高Al组分的AlGaN外延层,最理想的衬底应是AlN,AlN晶体对波长大于200nm的紫外光都是透明的,并且AlN与AlGaN可以形成较好的晶格匹配,AlN还具有较好的热导性(热导率3Wcm -1 K -1 ),有利于提高器件的大功率性能.除此之外,由于在所有已知的声表面波材料中具有最大的声速(6200m / s)、较高的压电耦合系数,AlN还是一种理想的射频声表面波材料;但是,目前国内外AlN单晶衬底的制备技术还不成熟,价格昂贵,而且供货困难(尤其是大尺寸衬底)。 [0004] 2006年,SoukhoveevV等人报道了采用HVPE(氢化物气相外延)方法成功地在蓝宝石衬底上生长出高质量的AlN模板,但由HVPE方法得到的AlN模板无法以原位生长方式制作后续的器件外延结构,因此工艺过程相对复杂,从降低工艺复杂度的方面考虑,有必要探索用MOCVD方法在蓝宝石衬底上直接生长AlN模板的技术。 Contents of the invention [0005] 针对背景技术中的问题,本发明提出了一种在蓝宝石衬底上生长外延用AlN模板的方法,其创新在于:以三甲基铝为MO源,NH 3 为气态源,采用金属有机物化学汽相沉积工艺在蓝宝石表面生长出AlN模板;在生长AlN模板时,三甲基铝先于NH 3 通入反应室内,通入三甲基铝后延迟1-5秒再通入NH 3 , NH 3 与附着在蓝宝石表面的Al原子发生反应后生成AlN,最终在蓝宝石表面生长出AlN模板;NH 3 和三甲基铝的Ⅴ / ...

AI Technical Summary

Problems solved by technology

[0002] At present, the nitride epitaxial growth technology based on sapphire / GaN is very mature at home and abroad, but for deep ultraviolet optoelectronic devices, the luminous efficiency of the device will be seriously reduced due to the strong absorption of GaN materials on ultraviolet light. The incident light will be absorbed by the GaN layer and cannot enter the active region to generate photocurrent. Therefore, the nitride template based on sapphire / GaN is not suitable for making deep ultraviolet optoelectronic devices; in order to solve the above problems, a more feasible technology The route is: discard the GaN template, and directly grow an AlGaN epitaxial layer with a high Al composition on a sapphire substrate that has good transmission properties for deep ultraviolet light

[0003] To grow AlGaN epitaxial layer with high Al composition, the most ideal substrate should be AlN, AlN crystal is transparent to ultraviolet light with a wavelength greater than 200nm, and AlN and AlGaN can form a good lattice match, and AlN also has relatively Good thermal conductivity (thermal conductivity 3Wcm -1 K -1 ), which is conducive to improving the high-power performance of the device. In addition, due to the highest sound velocity (6200m / s) and high piezoelectric coupling coefficient among all known surface acoustic wave materials, AlN is also an ideal radio frequency surface acoustic wave material; however, currently The preparation technology of outer AlN single crystal substrate is immature, expensive, and difficult to supply (especially large-scale substrates)

[0004] In 2006, SoukhoveevV et al. reported that the HVPE (Hydride Vapor Phase Epitaxy) method was used to successfully grow high-quality AlN templates on sapphire substrates, but the AlN templates obtained by the HVPE method could not be grown in situ. Subsequent devices Epitaxial structure, so the process is relatively complicated. From the perspective of reducing process complexity, it is necessary to explore the technology of directly growing AlN template on the sapphire substrate by MOCVD method