Transport properties of highly conductive n-type Al-rich Al _xGa _1-xN (x≥0.7)

We report here the growth and transport studies of conductive n-type Al _xGa _1-xN alloys with high Al contents (x ≥ 0.7). Si-doped Al _xGa _1-xN alloys were grown by metalorganic chemical vapor deposition on AlN-epilayer/sapphire substrates with very smooth surface. Low n-type resistivities have been obtained for Al-rich Al _xGa _1-xN alloys. The resistivity was observed to increase rapidly with increasing x due to the deepening of the Si donor energy level. Transport measurements have indicated that we have achieved n-type conduction in pure AlN. From the temperature dependence of the resistivity, the donor activation energy was estimated to vary from 23 to 180 meV as x was increased from 0.7 to 1.0.