High Mobility Cd3As2(112) on GaAs(001) Substrates Grown via Molecular Beam Epitaxy

Anthony D Rice,Jocienne Nelson,Patrick Walker,Kirstin Alberi,Andrew G Norman

doi:10.1021/acsaelm.1c01126

Anthony D Rice, Jocienne Nelson + Show 3 more

Open Access

https://doi.org/10.1021/acsaelm.1c01126

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Abstract

The three-dimensional Dirac semimetal Cd3As2 exhibits ultrahigh electron mobilities that are attractive for optoelectronic devices. However, its strong propensity to grow in the (112) orientation limits the feasibility to epitaxially integrate it into semiconductor structures that are conventionally grown in the (001) orientation. Here, we demonstrate a route to epitaxially growing high mobility Cd3As2(112) layers on GaAs(001) substrates, opening up possibilities for device design. The (001) crystallographic orientation of the GaAs substrate is switched to the (111) orientation through a strain-driven process at a CdTe/GaAs interface, resulting in a CdTe(111) buffer layer on top of which Cd3As2 can be grown. Although the CdTe(111) buffer layer templates Cd3As2 in the (112) orientation, it is not sufficient for producing Cd3As2 with high electron mobility. We therefore demonstrate additional buffer layer design principles for realizing Cd3As2(112) epilayers with similar electron mobilities to those grown on lattice-mismatched III–V (111) substrates. Finally, we outline a pathway to use this approach to grow Cd3As2(112) epilayers on Si(001) substrates, further expanding the potential to integrate Cd3As2 into electronic devices.

Highlights

Three-dimensional (3D) topological semimetals, characterized by the presence of bulk and surface band touching nodes, offer ultrahigh carrier mobilities and strong broadband optical absorption that are advantageous for optoelectronic applications
Dirac semimetal Cd3As2 is among the most studied topological semimetals and is an excellent candidate for integration, as it is air stable and has already been epitaxially grown on a variety of conventional semiconductor substrates.[1−8] A challenge to realizing high performance and scalable devices will be to control integration such that both Cd3As2 and semiconductor layers can be grown in their preferred crystallographic orientations to improve their properties, reduce defects, and enhance surface smoothness necessary for heteroepitaxy
Following removal of the As cap at 350 °C, the on-axis GaAs(001) structure was briefly annealed at 500 °C to remove As from the surface, creating a Ga-rich, c(8 × 2) reconstruction measured by reflection high energy electron diffraction (RHEED)

Summary

Introduction

Three-dimensional (3D) topological semimetals, characterized by the presence of bulk and surface band touching nodes, offer ultrahigh carrier mobilities and strong broadband optical absorption that are advantageous for optoelectronic applications. To exploit these properties, effective strategies for integrating them into semiconductor heterostructures must be developed. Growth of Cd3As2 along its higher energy (001) surface was demonstrated on a GaSb(001) substrate,[13] using an InAs wetting layer to improve nucleation These layers have similar electron mobilities to (112) oriented films, but their surfaces form an undesirable 3D morphology. The conductivity of GaSb substrates and low band gaps of InAs can form alternate conduction channels that are not practical for device applications

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