Trace impurities of vanadium in Lely-grown silicon carbide single crystals have been detected by their strong, polytype-specific photoluminescence in the 1.3-1.5 mym near-infrared spectral rang, as well as by infrared absorption. A high 0/A high-, and possibly also as a deep donor. The role of vanadium as minority-carrier lifetime killer in SiC-based optoelectronic devices is suggested from these data
A characteristic infrared luminescence spectrum, dominated by a zero-phonon line at 1.30 eV, has been observed on AlN polycrystalline material. It is assigned to the spin-forbidden internal 3d–3d transition 4T1(G)→6A1(S) of Fe3+Al(3d5). By photoluminescence excitation spectroscopy the (-/0) acceptor level of iron in AlN could be located at EV+3.0 eV. The corresponding value for iron in GaN is EV+2.5 eV. From these values, the valence-band offset in AlN/GaN heterojunctions is predicted as ΔEV=0.5 eV, the conduction-band offset as ΔEC=2.3 eV.
A characteristic infrared luminescence band, dominated by a zero-phonon line at 1.30 eV has been consistently detected in gallium nitride (GaN) epitaxial layers. It is assigned to the intra-3d-shell transitions 4T1(G)→6A1(S) of omnipresent iron trace impurities, Fe3+Ga(3d5). Another infrared emission is often also observed at 1.19 eV. This is tentatively assigned to chromium trace impurities, Cr4+Ga(3d2). The role of iron and chromium as minority-carrier lifetime killers in GaN-based optoelectronic devices is suggested from these data.
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