Electrical characterization of hydrogenated n-type AlGaN

We investigated two series of MOCVD-grown Al_xGa1-xN samples with Al compositions x=0.1 and x=0.3 before and after hydrogenation. Shallow and deep centers were investigated using electrical characterization methods. We observe a dominant donor level with a larger binding energy in the sample with x=0.3. We also observe interface defects between An and the AlGaN layer which become more significant with increasing x. Their presence is related to the high Al mole fraction which creates potential fluctuations at the surface of the sample. Hydrogenation results in (i) a partial passivation of the shallow donors, (ii) disappearance of interface defects, and (iii) creation of a new shallow donor center.