Photoluminescence Characterization of Defects Introduced in 4H-SiC During High Energy Proton Irradiation and Their Annea
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J5.21.1
Photoluminescence Characterization of Defects Introduced in 4H-SiC During High Energy Proton Irradiation and Their Annealing Behavior M. Ahoujja,1 H. C. Crocket,2 M. B. Scott, 2 Y.K. Yeo,2 and R. L. Hengehold2 1 2
Department of Physics, University of Dayton, Dayton, OH, USA Air Force Institute of Technology, Wright-Patterson AFB, OH, USA
ABSTRACT We report on the optical properties of defects introduced in epitaxial 4H-SiC by 2 MeV protons using photoluminescence spectroscopy. The near band edge characteristics of nitrogen-doped n-type 4H-SiC are present in the optical spectrum of the as-grown samples. Following a proton irradiation, the material is altered and the luminescence of the shallow centers is attenuated almost entirely with the emergence of deeper shallow traps at energies greater than 300 meV below the conduction band. Subsequent hightemperature thermal annealing of the material results in an increase in the emission spectrum at both the near band edge region (Eg = 3.25 eV) and between 2.65 and 2.95 eV. Recovery of the characteristic nitrogen-related peaks at the near band edge following high-temperature annealing is identified, but is not complete even at 1500 oC. In the deep trap region below 2.95 eV, activation of trap centers with annealing results in a sharp increase in the signal intensity of an irradiation-induced defect trap (2.90 eV) as well as the associated phonon replicas. Based on previous ion-implantation and other radiation studies in 4H-SiC, the emergence of the 2.90 eV defect complex and associated phonon replicas after high temperature anneal is the well known D1 photoluminescence. The observed lines in the D1 spectrum are due to exciton recombination at isoelectronic defect centers. INTRODUCTION SiC’s wide bandgap, high electron saturation velocity, and other superior electrical and thermal properties make it a potential candidate for high power electronic devices that can operate in high temperature and caustic environments.[1] Due to its radiation hardness, 4H-SiC is considered as one of the leading wide band gap materials for space applications. Two types of penetrating radiation in space are high energetic electrons and protons. These high energy particles give rise to a wide range of deep level defect centers such as vacancies and interstitials [2] which are ultimately responsible for degrading satellites on-board electronic components and inducing background noise in detectors and errors in digital circuits.[3] Therefore, a clearer understanding of how SiC films and SiC-based devices behave under a radiation environment is required before SiC devices are incorporated in space applications. As a result, defects introduced in 6H-SiC and 4H-SiC by irradiations including electrons, protons, neutrons and ion implants, have been intensively investigated using electrical [4,5] and optical [6,7] techniques. In this letter, we report on the optical characterization of proton irradiated 4H-SiC using photoluminescence (PL) measurements. The influence of proton irradiation on elec
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