High structural quality In N ∕ In 0.75 Ga 0.25 N multiple quantum wellsgrown by molecular beam epitaxy

In N ∕ In 0.75 Ga 0.25 N multiple quantum wells (MQWs) were grown by rf plasma-assisted molecular beam epitaxy. The high-resolution transmission electron microscope and x-ray diffraction measurements showed evidence of growth of atomically smooth and sharp interface and good periodicity. Room-temperature photoluminescence emissions from InN quantum wells were observed at the wavelength range from 1.59 to 1.95 μ m by changing the well thickness. The unstrained valence band offset of In N ∕ Ga N was estimated to be Δ E v = 0.9 eV by comparing the experimental transition wavelengths of the MQWs and a theoretical calculation considering strain effects and built-in, mainly piezoelectric, fields.