Crack-free and conductive Si-doped AlN∕GaN distributed Bragg reflectors grown on 6H-SiC(0001)

We demonstrate Si-doped $n$ -type $\mathrm{Al}\mathrm{N}∕\mathrm{Ga}\mathrm{N}$ distributed Bragg reflectors grown on 6H-SiC(0001). The structures are crack-free and have a stopband centered around $450\mathrm{nm}$ with a full width at half maximum between 40 and $50\mathrm{nm}$ . The maximum measured reflectance is $⩾99\%$ . A comparison between Si-doped and undoped structures reveals no degradation of the reflectance due to the Si doping. Vertical conductance measurements at room temperature on the samples show an ohmic $I\text{–}V$ behavior in the entire measurement range. The measured resistivity at $77\mathrm{K}$ is only a factor of 2 larger than the resistivity measured at room temperature.