Reduction of threading dislocation density in Ge/Si using a heavily As-doped Ge seed layer

Kwang Hong Lee,Cong Wang,Jurgen Michel,Bing Wang,Shuyu Bao,Chuan Seng Tan,Soon Fatt Yoon,Eugene A Fitzgerald

doi:10.1063/1.4943218

Abstract

High quality germanium (Ge) epitaxial film is grown directly on silicon (001) substrate with 6° off-cut using a heavily arsenic (As) doped Ge seed layer. The growth steps consists of (i) growth of a heavily As-doped Ge seed layer at low temperature (LT, at 400 °C), (ii) Ge growth with As gradually reduced to zero at high temperature (HT, at 650 °C), (iii) pure Ge growth at HT. This is followed by thermal cyclic annealing in hydrogen at temperature ranging from 600 to 850 °C. Analytical characterization have shown that the Ge epitaxial film with a thickness of ∼1.5 µm experiences thermally induced tensile strain of 0.20% with a treading dislocation density (TDD) of mid 106/cm2 which is one order of magnitude lower than the control group without As doping and surface roughness of 0.37 nm. The reduction in TDD is due to the enhancement in velocity of dislocations in an As-doped Ge film.

Highlights

The growth of germanium (Ge) epitaxial layer on silicon (Si) substrate has attracted great attention among researchers recently because of its potential applications in photonic and electronics devices.[1,2,3,4] Most importantly, Ge is a group IV material, making it compatible with Si and can be processed in a standard silicon manufacturing facility
Another important application is that the Ge-on-Si substrate (Ge/Si) can be used as a template for subsequent III-V compounds growth since Ge is lattice-matched with gallium arsenide (GaAs).[5]
No visible TD is observed under X-transmission electron microscopy (TEM), indicating that a the surface of the Ge film has < 108 threading dislocations per cm[2] obtained during the high temperature pure Ge growth

Summary

INTRODUCTION

The growth of germanium (Ge) epitaxial layer on silicon (Si) substrate has attracted great attention among researchers recently because of its potential applications in photonic and electronics devices.[1,2,3,4] Most importantly, Ge is a group IV material, making it compatible with Si and can be processed in a standard silicon manufacturing facility Another important application is that the Ge-on-Si substrate (Ge/Si) can be used as a template for subsequent III-V compounds growth since Ge is lattice-matched with gallium arsenide (GaAs).[5] The desired Ge epitaxial film must have low defect density (in term of threading dislocation density, TDD), smooth surface with thin buffer layers. Ge seed layer and the details will be discussed

EXPERIMENTAL DETAILS

RESULTS AND DISCUSSION

CONCLUSION