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Band Gap Engineering of Nano Scale AlGaN Epitaxial Layers by Swift Heavy Ion Irradiation

Published online by Cambridge University Press:  31 January 2011

SATHISH N
Affiliation:
rnsathish@yahoo.com, University of Hyderabad, School of Physics, Hyderbad, AP, India
Devaraju G
Affiliation:
devaraju_hcuin@yahoo.co.in, University of Hyderabad, School of Physics, Hyderbad, AP, India
Srinivasa Rao N
Affiliation:
srinivasarose@yahoo.co.in, University of Hyderabad, School of Physics, Hyderbad, AP, India
Anand Pathak
Affiliation:
appsp@uohyd.ernet.in, University of Hyderabad, Physics, School of Physics, University of Hyderabad, Hyderabad, A P, 500046, India, +91 40 23010181 / 23134316, +91 40 23010181 / 23010227
Andrzej Turos
Affiliation:
andrzej.turos@itme.edu.pl, Institute of Electronic Materials Techonology, Warsaw, Poland
S A Khan
Affiliation:
saif@iuac.ernet.in, Inter-University Accelerator Centre, New Delhi, India
D K Avasthi
Affiliation:
dka@iuac.ernet.in, Inter-University Accelerator Centre, New Delhi, India
E Trave
Affiliation:
trave@padova.infm.it, Università di Padova, Dip. Fisica “G.Galilei”, Padova, Italy
P Mazzoldi
Affiliation:
mazzoldi@padova.infm.it, Università di Padova, Dip. Fisica “G.Galilei”, Padova, Italy
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Abstract

Epitaxial AlGaN/GaN layers grown by MBE on SiC substrates were irradiated with 150 MeV Ag ions at a fluence of 5×1012 ions/cm2. AlGaN/GaN MQWs were grown on Sapphire substrate by MOCVD and irradiated with 200 MeV Au8+ ions at a fluence of 5×1011 ions/cm2 . These samples were used to study the effects of SHI on optical properties of AlGaN/GaN based nano structures. RBS/Channelling strain measurements were carried out at off normal axis of irradiated and unirradiated samples. In as grown samples, AlGaN layer is partially relaxed with a small compressive strain. After irradiation this compressive strain increases by 0.22% in AlGaN layer. Incident ion energy dependence of dechannelling parameter shows E1/2 dependence, which corresponds to the dislocations. Defect densities were calculated from the E1/2 graph. As a result of irradiation defect density increased on both GaN and AlGaN layer. Optical properties of AlGaN/GaN MQWs before and after irradiation have been analyzed using PL. This study shows that SHI increase the confinement effects in the MQWs and intensity of the active layer of the MQWs luminescence is increased by one order. This may be due to the induced strain in GaN and AlGaN layers. Some unwanted yellow luminescence has also been introduced by the SHI possibly due the point defects or defect luminescence from the induced dislocations in GaN bulk epitaxial layers. In this study, we present some new results concerning high energy irradiation on AlGaN/GaN heterostructures and MQWs characterized by RBS/Channelling and PL.

Type
Research Article
Copyright
Copyright © Materials Research Society 2009

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References

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