Strain modification of AlGaN layers using swift heavy ions

Abstract

Epitaxial AlGaN/GaN layers grown by molecular beam epitaxy (MBE) on SiC substrates were irradiated with 150 MeV Ag ions at a fluence of 5×10¹² ions/cm². The samples used in this study are 50 nm Al_0.2Ga_0.8N/1 nm AlN/1 μ m GaN/0.1 μ m AlN grown on SI 4H-SiC. Rutherford backscattering spectrometry/channeling strain measurements were carried out on off-normal axis of irradiated and unirradiated samples. In an as-grown sample, AlGaN layer is partially relaxed with a small tensile strain. After irradiation, this strain increases by 0.22% in AlGaN layer. Incident ion energy dependence of dechanneling parameter shows E ^1/2 dependence, which corresponds to the dislocations. Defect densities were calculated from the E ^1/2 graph. As a result of irradiation, the defect density increased on both GaN and AlGaN layers. The effect of irradiation induced-damages are analyzed as a function of material properties. Observed results from different characterization techniques such as RBS/channeling, high-resolution XRD and AFM are compared and complemented with each other to deduce the information. Possible mechanisms responsible for the observations have been discussed in detail.

Keywords:

• III-Nitrides
• RBS/channeling
• HRXRD and swift heavy ions

PACS :

• 61.72.Dd
• 61.85+p

Acknowledgements

N.S. thanks UGC-DAE-CSR, Anupuram Node for fellowship through a project granted to APP. The samples for this study were kindly provided by Dr D. Scott Katzer and we warmly thank him for this. We also thank Dr B.B. Rath for his supports for this collaboration vide an NRL research project no. N00014-97-1-0994.