Growth of nonpolar cubic GaN/AlN multiple quantum wells with intersubband transitions for 1.5 μm applications

Cubic GaN/AlN short-period multiple quantum well structures were grown at 720 degrees C by plasma-assisted molecular beam epitaxy on free standing 3C-SiC substrates. The samples consist of 100 nm thick GaN buffer and 20 periods of GaN/AlN active regions. The thickness of the AlN barrier is 1.35 nm for all samples, while the thickness of the GaN well varies between 1.6 nm-2.10 nm depending on the samples. The periodicity of the GaN/AlN active regions was confirmed by the presence of several peaks in the high resolution x-ray diffraction (HRXRD) spectra. The thickness of the total period was estimated by fitting the HRXRD data using a dynamic scattering theory. Room temperature measurements of the optical absorption spectra of the intersubband transitions were obtained using a Bruker IFS-125HR spectrometer. The peak position wavelengths of these transitions were observed in the spectral region of 1.5-2.0 mu m and confirmed theoretically by using a self-consistent Poisson-Schrodinger model.