Van der Waals (VdW) Bonding, GaAs on Si and Graphene as a Buffer Layer

Figure 1: a) Atomic geometry of GaAs/multi-layer graphene/Si interface showing only top-most graphene layer is strained by heteroepitaxial growth, b) schematic for structure with GaAs grown on top of single-layer graphene buffer layer/Si substrate. (Image source: http://www.semiconductor-today.com/news_items/2014/SEP/UCLA_100914.shtml and http://onlinelibrary.wiley.com/doi/10.1002/adfm.201400960/abstract)
Figure 1: a) Atomic geometry of GaAs/multi-layer graphene/Si interface showing only top-most graphene layer is strained by heteroepitaxial growth, b) schematic for structure with GaAs grown on top of single-layer graphene buffer layer/Si substrate. (Image source: http://www.semiconductor-today.com/news_items/2014/SEP/UCLA_100914.shtml and http://onlinelibrary.wiley.com/doi/10.1002/adfm.201400960/abstract)
Ok, In this post I will try to summarize this paper, one sentence at every question.

Introduction

Why is this important?

Photonics devices based on the integration of III-V materials (in this case is GaAs) on Si.

What needs to be done?

Heteroepitaxial growth using MBE utilizing 2D material, owning to its VdW bonding which yields to accomodation to lattice mismatch between 3D-2D material.

What has been done already?

MBE-grown GaAs NWs on graphene/Si substrate (A. M. Munshi et al, Nano Lett.2012124570), MOCVD-grown InAs/In(x)Ga(1-x)As NWs on graphene (P. K. Mohseni et alNano Lett. 2013131153) and GaAs/Si using layered GaSe (J. E. Palmer et al, J. Cryst. Growth 1995150685).

Goal of the Research Project

Using graphene as a buffer layer in realizing VdW epitaxial growth of GaAs on Si

Method

First, Y. Alaskar et al calculated surface energy of the graphene buffer layer with Ga and As prelayer; adsorption and migration energy of Al, Ga, In and As on graphene; The experimental is divided in fabrication (mechanical exfoliation of graphene and growing using MBE) and characterization (FESEM, AFM, Raman spectroscopy and XRD)

Result

Theoretical result will not be presented in here, and instead, we focus on experimental result: (i) due to the low surface energy of graphene triggering high tension toward GaAs and (ii) low adsorption and mitigation energy of Ga and As on graphene at high temperature, island growth (3D) is formed instead of single crystal (2D) of GaAs

Challenges and Bottlenecks

Developing understanding of VdW interaction between GaAs/graphene/Si

Opportunities and Workarounds

Two-step growth is employed to investigate graphene using Ga- or As- prelayer.

 

Important: Growth morphology-surface energy, nucleation step-thin film properties, low surface energy of graphene, low adsorption energy of Ga and As, nucleation site, surface energy-adsorption energy, surface energy-growth temperature-wettability-nucleation process,

 

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