Polarity Control in Group-III Nitrides beyond Pragmatism
Polarity Control in Group-III Nitrides beyond Pragmatism
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DOI：
10.1103/physrevapplied.5.054004
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发表时间：
2016-05-03
影响因子：
4.6
通讯作者：
Albrecht, Martin
中科院分区：
文献类型：
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作者：
Mohn, Stefan;Stolyarchuk, Natalia;Albrecht, Martin
在非极性衬底上控制极性半导体的极性以异质结的形式提供了大量的器件概念。实现此类结构的关键是合适的缓冲层设计，过去这是通过经验发展起来的。蓝宝石上的氮化镓或氧化锌就是这方面的突出例子。然而，理解介导极性的基本过程仍然是一个未解决的问题。在这项工作中，我们以蓝宝石上的III族氮化物为例，通过透射电子显微镜研究缓冲层的结构。我们表明，是蓝宝石表面转化为菱面体氮氧化铝层，将初始的N极性表面转变为Al极性。由于赝二元Al₂O₃ - AlN体系的各种AlₓOᵧNₙ相及其对本征缺陷（氧化物所特有的）的耐受性，使得蓝宝石中八面体配位的Al和AlN中四面体配位的Al之间的平滑过渡成为可能。基于这些结果，我们讨论了实现任意一种极性的影响，并阐明了III族氮化物领域中广泛应用的概念，如氮化和低温缓冲层。
Controlling the polarity of polar semiconductors on nonpolar substrates offers a wealth of device concepts in the form of heteropolar junctions. A key to realize such structures is an appropriate buffer-layer design that, in the past, has been developed by empiricism. GaN or ZnO on sapphire are prominent examples for that. Understanding the basic processes that mediate polarity, however, is still an unsolved problem. In this work, we study the structure of buffer layers for group-III nitrides on sapphire by transmission electron microscopy as an example. We show that it is the conversion of the sapphire surface into a rhombohedral aluminum-oxynitride layer that converts the initial N-polar surface to Al polarity. With the various AlxOyNz phases of the pseudobinary Al2O3-AlN system and their tolerance against intrinsic defects, typical for oxides, a smooth transition between the octahedrally coordinated Al in the sapphire and the tetrahedrally coordinated Al in AlN becomes feasible. Based on these results, we discuss the consequences for achieving either polarity and shed light on widely applied concepts in the field of group-III nitrides like nitridation and low-temperature buffer layers.