Si-doped AlxGa1-xN(0.56≤ x ≤1) layers grown by molecular beam epitaxy with ammonia -: art. no. 132106

We describe experiments on Si doping in AlxGa1-xN grown by gas source molecular beam epitaxy with ammonia and silane. Growth conditions that minimize self-compensation were used to assure Si incorporation at a level of 2x10(20) cm(-3) for the entire range of compositions investigated, from x=0.56 to 1.0. These conditions resulted in donor concentrations of similar to 1x10(19) cm(-3) up to x=0.85. Layers of AlxGa1-xN up to x=0.85 show good mobility and low resistivity. In these layers, the activation energy, E-a, of Si stays below similar to 25 meV and Si can be considered a shallow donor. For AlN content above x=0.85 the donor activation energy increases to E(a)similar to 250 meV in AlN. The change in donor activation energy correlates with increased incorporation of oxygen and carbon. (C) 2005 American Institute of Physics.