Optical Properties of High Energy Tin (Sn5+) Ion Irradiated Metal-Organic Chemical Vapor Deposition Grown GaN on Sapphire

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Unintentionally doped n-type GaN(0001) epitaxial layers grown by metal-organic chemical vapor deposition (MOCVD) on sapphire substrates have been irradiated with 75 MeV Tin (Sn5+) ion. Effect of different ion fluences at $10^{11}$, $10^{12}$ and $10^{13}$ cm-2 were studied by means of time correlated single photon counting (TCSPC), UV-visible optical spectroscopy and photoluminescence (PL) measurements at room temperature. The exponential decay of minority carrier life times was observed between 1910 and 1110 ps (pico-second) with increasing ion doses upto $10^{13}$ cm-2. High-energy irradiation with different ion fluences of GaN epitaxial layers creates midgap states in the material. Change in the absorption edges between 3.41 and 2.95 eV were observed by UV-absorption coefficient ($\alpha^{2}$) method on increasing fluences rate. Band-edge and yellow emissions were recorded for all GaN samples by transient steady state PL measurement at room temperature.
2004-07-15