Yongjin Cho’s paper is Editor’s Pick in Applied Physics Letters

Yongjin Cho, research associate in electrical and computer engineering, is the lead author of a new paper published by the journal Applied Physics Letters. The paper titled “Molecular beam homoepitaxy on bulk AlN enabled by aluminum-assisted surface cleaning” was selected as an Editor’s Pick. ECE Professors Huili Grace Xing and Debdeep Jena are among the paper’s co-authors.

The research examines the effectiveness using aluminum to assist in the cleaning of native surface oxides of bulk AlN. 

“Native surface oxide of AlN substrate has been a major obstacle to the success of high quality sample growth on AlN substrate by molecular beam epitaxy (MBE),” said Cho. “In this study, we found that Al-assisted cleaning is an easy and effective way to remove such native surface oxides, and thus leads to high quality AlN growth.”

This deoxidation method will enable researchers to grow high quality AlGaN and AlN materials, which have applications in deep-ultraviolet optoelectronics. 

“As AlN bulk substrates with low defect densities are now commercially available,” Cho explained, “our finding is timely and will make significant impacts on the wide bandgap nitride semiconductor community.”

The “Editor’s Pick” designation from Applied Physics Letters distinguishes Cho’s paper, placing it among the most significant papers published by the journal this month. 

An image from the paper

[(a), (d), and (g)] Low magnification HAADF-STEM images, [(b), (e), and (h)] enlarged images, and [(c), (f), and (i)] symmetric XRD ω/2θ scans of AlN grown on AlN bulk substrates, the surface of which was not in situ cleaned [(a), (b), and (c)], was thermally cleaned [(d), (e), and (f)], and was Al-assisted cleaned [(g), (h), and (i)]. The notches in (a), (d), and (g) indicate the growth interface. A ball-and-stick model for Al-polar AlN is superimposed on (h), where the red balls indicate the Al atoms and the tiny gray balls are the N atoms. Note the absence of thickness fringes for the sample with Al-assisted cleaning.

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