Structural Property Study for GeSn Thin Films.

Liyao Zhang,Nils Von Den Driesch,Shumin Wang,Yuxin Song,Zhenpu Zhang,Dan Buca,Detlev Grützmacher

doi:10.3390/ma13163645

Abstract

The structural properties of GeSn thin films with different Sn concentrations and thicknesses grown on Ge (001) by molecular beam epitaxy (MBE) and on Ge-buffered Si (001) wafers by chemical vapor deposition (CVD) were analyzed through high resolution X-ray diffraction and cross-sectional transmission electron microscopy. Two-dimensional reciprocal space maps around the asymmetric (224) reflection were collected by X-ray diffraction for both the whole structures and the GeSn epilayers. The broadenings of the features of the GeSn epilayers with different relaxations in the ω direction, along the ω-2θ direction and parallel to the surface were investigated. The dislocations were identified by transmission electron microscopy. Threading dislocations were found in MBE grown GeSn layers, but not in the CVD grown ones. The point defects and dislocations were two possible reasons for the poor optical properties in the GeSn alloys grown by MBE.

Highlights

Since the first planar silicon (Si) transistor was invented in 1959 [1], the Si electronic industry has developed prosperously
We investigate the structural property differences of GeSn alloys with different Sn concentrations and thicknesses
We further study the differences of optical properties of GeSn samples grown by molecular beam epitaxy (MBE) and chemical vapor deposition (CVD) and their connections with the structural properties

Summary

Introduction

Since the first planar silicon (Si) transistor was invented in 1959 [1], the Si electronic industry has developed prosperously. The continuous scaling of the transistors has led to several problems, such as signal delays, higher power consumption, quantum limitations, etc. Without new technologies, the shrinking of the transistors will stop around 2021 [2]. Si photonics, which utilizes photons instead of electrons for information transmission and processing, is one of the promising solutions for these problems and shows a bright future [3,4]. It is difficult to fabricate light sources using Si due to its indirect bandgap nature. The light sources used in the commercial Si based circuits are made of group III-V materials, and bonded to the circuits at present [5]. The bonding technology hinders the future large-scale integration [3]

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Results

Conclusion