High-resolution X-ray diffraction analysis of strain distribution in GaN nanowires on Si(111) substrate.

Hryhorii Stanchu,Kamil Klosek,Nadiia Safriuk,Marta Sobanska,Zbigniew R Zytkiewicz,Alexander Belyaev,Andrian V Kuchuk,Aleksandra Wierzbicka,Vasyl Kladko

doi:10.1186/s11671-015-0766-x

Abstract

In this work, the influence of micro- and macro-deformation profiles in GaN nanowires (NWs) on the angular intensity distribution of X-ray diffraction are studied theoretically. The calculations are performed by using kinematical theory of X-ray diffraction and assuming the deformation decays exponentially from the NW/substrate interface. Theoretical modeling of X-ray scattering from NWs with different deformation profiles are carried out. We show that the shape of the (002) 2θ/ω X-ray diffraction profile (XDP) is defined by initial deformation at the NW's bottom and its relaxation depth given by the decay depth of the exponential deformation profile. Also, we demonstrate that macro-deformation leads to XDP shift, whereas micro-deformations are the cause of XDP's asymmetry and its symmetrical broadening. A good correlation between calculated and experimental XDP from self-assembled GaN NWs on Si(111) substrate was achieved by taking into account all parameters of micro- and macro-deformation profiles.

Highlights

The wide range of unique properties of semiconductor GaN nanowires (NWs), along with various techniques of NW's growth, makes them promising candidates for nano-sized optoelectronics [1]
We show that macrodeformations lead to X-ray diffraction profile (XDP) shift, whereas micro-deformations are the cause of XDP's asymmetry and its symmetrical broadening
As GaN NWs are bounded by free surfaces, the misfit deformation that is mainly concentrated at the NW/substrate heterointerface elastically relaxes to the NW's free sides

Summary

Introduction

The wide range of unique properties of semiconductor GaN nanowires (NWs), along with various techniques of NW's growth, makes them promising candidates for nano-sized optoelectronics [1]. The main sources of deterioration of NW's properties are their crystalline imperfection and residual strain. NWs are considered almost strain-free crystalline-objects without extended defects that propagate into their structure [2,3,4,5]. In comparison with thick planar epilayers, where the mechanism of lattice accommodation is preferably plastic and where the formation of misfit dislocation networks takes place, NWs are considered to be predominantly free of dislocations [6,7]. The process of deformation relaxation in NWs is not completely studied

Methods

Results

Conclusion