Intersubband Absorption at? ? 1.2-1.6 ?m in GaN/AlN Multiple Quantum Wells Grown by rf-Plasma Molecular Beam Epitaxy

In order to investigate the intersubband transition (ISBT), GaN/AlN multiple quantum wells with 90 GaN wells were prepared directly on (0001) sapphire substrates by rf-plasma molecular beam epitaxy. The thickness of GaN well and AlN barrier were 4–8 monolayers (ML) and ∼11 ML, respectively. One ML corresponds to around 2.6 Å. ISBT absorptions at 1.15–1.55 μm in wavelength, which covers the whole communication wavelength, were measured, and 1.15 μm is the shortest record in ISBT-wavelength.