YongJin Cho

Molecular beam homoepitaxy on bulk AlN enabled by aluminum-assisted surface cleaning

Publisher: AIP Publishing

Date: 27-04-2020

DOI: 10.1063/1.5143968

Abstract: We compare the effectiveness of in situ thermal cleaning with that of Al-assisted cleaning of native surface oxides of bulk AlN for homoepitaxial growth by molecular beam epitaxy. Thermal deoxidation performed at 1450 °C in vacuum results in voids in the AlN substrate. On the other hand, Al-assisted deoxidation at ≈900°C results in high-quality AlN homoepitaxy, evidenced by clean and wide atomic terraces on the surface and no extended defects at the growth interface. This study shows that Al-assisted in situ deoxidation is effective in removing native oxides on AlN, providing a clean surface to enable homoepitaxial growth of AlN and its heterostructures furthermore, it is more attractive over thermal deoxidation, which needs to be conducted at much higher temperatures due to the strong bonding strength of native oxides on AlN.

Excitonic and deep-level emission from N- and Al-polar homoepitaxial AlN grown by molecular beam epitaxy

Publisher: AIP Publishing

Date: 08-2023

DOI: 10.1063/5.0158390

Abstract: Using low-temperature cathodoluminescence spectroscopy, we study the properties of N- and Al-polar AlN layers grown by molecular beam epitaxy on bulk AlN{0001}. Compared with the bulk AlN substrate, layers of both polarities feature a suppression of deep-level luminescence, a total absence of the prevalent donor with an exciton binding energy of 28 meV, and a much increased intensity of the emission from free excitons. The dominant donor in these layers is characterized by an associated exciton binding energy of 13 meV. The observation of excited exciton states up to the exciton continuum allows us to directly extract the Γ5 free exciton binding energy of 57 meV.

Crystal orientation dictated epitaxy of ultrawide-bandgap 5.4- to 8.6-eV α-(AlGa)₂O₃on m-plane sapphire

Publisher: American Association for the Advancement of Science (AAAS)

Date: 06-01-2021

DOI: 10.1126/SCIADV.ABD5891

Abstract: Crystalline oxides spanning very broad 5.4- to 8.6-eV bandgaps are successfully grown on sapphire by MBE.

Paul Drude Institute For Solid State Electronics

Location: Germany

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Eindhoven University Of Technology

Location: Netherlands

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Yeungnam University

Location: Korea, Republic of

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University Of Nottingham

Location: United Kingdom of Great Britain and Northern Ireland

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University Of Notre Dame

Location: United States of America

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Cornell University

Location: United States of America

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