Transition Metals in GaN and Related Compounds

Electronic transitions in the 3d shell typically appear in GaN in the near-infrared region. Near-infrared PL spectra of naturally contaminated GaN are shown in FIGURE 1 (a) a sample grown by the sandwich technique on p-SiC substrates (see [2]) and (b) a sample grown by hydride vapour phase epitaxy (HVPE) on sapphire (see [3,4,10]). We observe no-phonon (NP) PL lines at 1.3 eV (Fe3+), 1.19 eV (Ti2+), 1.047 eV (Co2+ or Ni3+) and 0.931 eV (V3+). 

Comprehensive PL excitation spectroscopy (PLE) investigations of the Fe3+ ( Ti — 6Ai) luminescence in semi-insulating GaN samples reveal intracentre excitation processes via excited states of the Fe3+ centre [10]. NP lines resolved around 2.01 and 2.73 eV are attributed to the 6Ai(S)-4T2(G) and 

FIGURE 1 Near-infrared transition metal PL in GaN samples grown (a) on p-SiC substrate by the sublimation sandwich technique, and (b) on sapphire substrate bv HVPE. 

Excitation with various wavelengths revealed different Fe-related centres in semi-insulating samples [8,12], In addition to the 1.3 eV luminescence caused by Fe3+, we observe further NP lines at 1.268 eV and 1.286 eV (FIGURE 2). The long decay time of 2.6 ms for the 1.268 eV line indicates a spin-forbidden transition. It has tentatively been assigned to an Fe complex with a nearby donor [8,12]. 

FIGURE 2 Different Fe-related complexes (, ) appear in semi-insulating GaN crystals. 

---

A8.7 Yellow luminescence in GaN A8.8 Hydrogen and acceptor compensation in GaN A8.9 3d transition metals in GaN and related compounds A8.10 Er-doped GaN and AIN... 

---