Molecular Beam Epitaxy of 2D-layered Gallium Selenide on GaN substrates

Choong Hee Lee; Sriram Krishnamoorthy; Dante J. O'Hara; Jared M. Johnson; John Jamison; Roberto C. Myers; Roland K. Kawakami; Jinwoo Hwang; Siddharth Rajan

doi:10.1063/1.4977697

arXiv · 1610.06265

Molecular Beam Epitaxy of 2D-layered Gallium Selenide on GaN substrates

Choong Hee Lee·Sriram Krishnamoorthy·Dante J. O'Hara·Jared M. Johnson·John Jamison·Roberto C. Myers·Roland K. Kawakami·Jinwoo Hwang·Siddharth Rajan

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Abstract

Large area epitaxy of two-dimensional (2D) layered materials with high material quality is a crucial step in realizing novel device applications based on 2D materials. In this work, we report high-quality, crystalline, large-area gallium selenide (GaSe) films grown on bulk substrates such as c-plane sapphire and gallium nitride (GaN) using a valved cracker source for Se. (002)-oriented GaSe with random in-plane orientation of domains was grown on sapphire and GaN substrates at a substrate temperature of 350-450 C with complete surface coverage and smooth surface morphology. Higher growth temperature (575 C) resulted in the formation of single-crystalline {\epsilon}-GaSe triangular domains with six-fold symmetry confirmed by in-situ reflection high electron energy diffraction (RHEED) and off-axis x-ray diffraction (XRD). A two-step growth method involving high temperature nucleation of single crystalline domains and low temperature growth to enhance coalescence was adopted to obtain continuous (002)-oriented GaSe with an epitaxial relationship with the substrate. While six-fold symmetry was maintained in the two step growth, {\beta}-GaSe phase was observed in addition to the dominant {\epsilon}-GaSe in cross-sectional scanning transmission electron microscopy images. This work demonstrates the potential of growing high quality 2D-layered materials using molecular beam epitaxy and can be extended to the growth of other transition metal chalcogenides.

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Choong Hee Lee, Sriram Krishnamoorthy, Dante J. O'Hara, Jared M. Johnson, John Jamison, Roberto C. Myers, Roland K. Kawakami, Jinwoo Hwang, Siddharth Rajan. 2016-10-20. Molecular Beam Epitaxy of 2D-layered Gallium Selenide on GaN substrates. https://doi.org/10.1063/1.4977697

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