Conductive and crack-free AlN/GaN:Si distributed Bragg reflectors grown on 6H-SiC(0Â 0Â 0Â 1)

We present n-type AlN/GaN:Si distributed Bragg reflectors grown on 6H-SiC(0 0 0 1) by plasma-assisted molecular beam epitaxy. The structures are free of cracks and exhibit a stopband centered around 450 nm with a FWHM between 40 and 50 nm. The measured reflectance is ⩾99%. A comparison between Si-doped and undoped structures shows no degradation of the reflectance due to the Si-doping. Vertical conductance measurements performed at room temperature on the samples show ohmic I-V behavior in the entire measurement range. The resistivity at 77 K is only two times larger than the resistivity at room temperature.