Strain distribution in single, suspended germanium nanowires studied using nanofocused x-rays

Mario Keplinger,Dominik Kriegner,Alois Lugstein,Johan Persson,Raphael Grifone,Julian Stangl,Johannes Greil,Tobias Schülli

doi:10.1088/0957-4484/27/5/055705

Abstract

Within the quest for direct band-gap group IV materials, strain engineering in germanium is one promising route. We present a study of the strain distribution in single, suspended germanium nanowires using nanofocused synchrotron radiation. Evaluating the probed Bragg reflection for different illumination positions along the nanowire length results in corresponding strain components as well as the nanowire's tilting and bending. By using these findings we determined the complete strain state with the help of finite element modelling. The resulting information provides us with the possibility of evaluating the validity of the strain investigations following from Raman scattering experiments which are based on the assumption of purely uniaxial strain.

Highlights

We present a study of the strain distribution in single, suspended germanium nanowires using nanofocused synchrotron radiation
The need for high-efficiency light emitting semiconductor devices based on silicon technology drives the efforts to alter the band structure of germanium, which has proven to be a good companion for state of the art silicon technology [1,2,3]
We present nanofocused x-ray diffraction (XRD) experiments and perform complementary finite element method (FEM) [22] modelling to provide a detailed insight into the strain state of tensile strained suspended Ge NWs

Summary

Introduction

Electron–hole recombination from the lowest energy valleys is only possible in connection with impurity and phonon scattering, rendering this recombination inefficient as compared to direct band-gap materials. For this reason, the goal of numerous investigations is to make germanium a direct semiconductor. Alloying Ge with Sn was reported to result in direct band-gap behaviour [13], and even lasing has been demonstrated recently [14] despite difficult material control due to the low solubility of Sn in Ge

Methods

Results

Conclusion