Basic properties of ternary group III nitride compound semiconductor non-polar surfaces

基于纤锌矿结构III族氮化物的新型半导体器件的开发不能仅仅依赖于二元化合物，即GaN， AlN和InN，因为只有三元（Al,Ga,In）N化合物才能提供设计所需的电子/光电特性的可能性。为了以自下而上的方式控制器件性能，对三元III族氮化物半导体材料的基本性能和物理特性有详细的微观和光谱理解是必要的。然而，对这些性质进行直接实验是一项相当困难的任务，因为只有表面敏感的测量才能提供足够分辨率的微观和光谱信息，因此，总体性质通常被极性III族氮化物表面的非化学计量层所隐藏。这可以通过研究非极性表面来避免，它允许探测体积和表面性质。此外，它们在技术上与纤锌矿结构纳米线相关。因此，我们提出研究三元III族氮化物半导体非极性表面的基本性质。目的是确定(i)本征表面状态，它们的空间定位和能级，以及表面带隙；（ii）费米能级钉钉和（iii）电子积累效应的物理起源；（iv）不同化合物的电子亲和力；(v)晶格应变和（vi）掺杂对基本性质的影响；（vii）对三元合金进行微观和光谱研究，以确定聚类、波动、有序。以及生长依赖效应，最后（八）缺陷分析，如螺纹位错、台阶、界面错配位错及其外在状态。有了这样一个全面的了解，基于III族氮化物的电子/光电器件的设计可以变得更加有效。

The development of novel semiconductor devices based on wurtzite structure group III nitrides cannot rely solely on the binary compounds, i.e. GaN, AlN, and InN, since only ternary (Al,Ga,In)N compounds offer the possibility to engineer the desired electronic/optoelectronic properties. In order to control device properties in a bottom-up fashion, a detailed microscopic and spectroscopic understanding of the fundamental properties and physics of the ternary group III nitrides semiconductor materials is necessary. A direct experimental access to these properties is, however, a rather difficult task, since only surface sensitive measurements can provide such microscopic and spectroscopic information with sufficient resolution and hence bulk properties are typically hidden by non-stoichiometric ad-layers on polar group III nitride surfaces. This can be avoided by investigating non-polar surfaces, which allow for probing both bulk and surface properties. In addition, they are technologically relevant for wurtzite structure nanowires. Therefore, we propose to investigate basic properties of ternary group III nitride compound semiconductor non-polar surfaces. The objectives are to determine (i) intrinsic surface states, their spatial localization and energy levels, as well as the surface band gaps, (ii) the physical origin of the Fermi-level pinning and (iii) of electron accumulation effects, (iv) the electron affinities for the different compounds, (v) the effect of lattice strain and (vi) of doping on the basic properties, (vii) a microscopic and spectroscopic investigation of the ternary alloys to determine clustering, fluctuations, ordering, as well as growth dependent effects, and finally (viii) the analysis of defects, such as threading dislocations, steps, interface misfit dislocations, and their extrinsic states. With such a comprehensive understanding the design of electronic/optoelectronic devices based on group III nitrides can be turned much more effective.