Low energy excitons in GaN film under strong magnetic fields

We investigate magneto- far-infrared (FIR) transmission on a 100 μm thick GaN film, which is grown on a Si/HR-GaN substrate. Under zero magnetic (B) fields, we observe three absorption peaks, which are located at the energy of 30.6 meV (Peak I), 34.7 meV (II), and 40.0 meV (III), respectively. Under perpendicular B-fields, small energy shifts of the three absorption peaks (I, II, III) are all linear to B. Meanwhile, peak II splits into two distinct peaks, with a distance about 0.08 meV/T in between. And three distinct splits are observed around Peak III with a distance of about 0.11 meV/T between neighbor peaks. We propose that the patterns of the absorption can be attributed to the low energy excitons in GaN under strong magnetic fields.