Nitrogen and copper doping in MgxZn1−xO films and their impact on p-type conductivity

Abstract

We report on nitrogen (N) and copper (Cu) doping in MgxZn1−xO films grown via remote-plasma-enhanced metalorganic chemical vapor deposition and their impact on p-type conduction. The MgxZn1−xO films showed a transformation of conductivity from n-type to p-type with increasing Mg content (x), which occurred at x = 0.078 with N2 carrier gas and x = 0.106 with H2 carrier gas. A comparison of the temperature dependent photoluminescence and the Hall effect measurement data revealed that the transformation of the conduction type with the increasing Mg content of MgxZn1−xO films is due to a conduction band up shift that causes the enhancement of the activation energy of donor states and the reduction of n-type residual electron concentrations. The p-type conductivity of MgxZn1−xO films with a low value of Mg content with N2 carrier gas was due to the contribution from the (N)O acceptor. Though N doped MgxZn1−xO (MgxZn1−xO:N) films showed p-type conductivity for x > 0.078, the N and Cu co-doped MgxZn1−xO (MgxZn1−xO:Cu,N) films showed n-type conduction with larger electron concentrations. Despite being a good acceptor, Cu doped MgxZn1−xO films had an n-type conductivity that was due to the contribution from shallow donors such as Cui and CusZni. Moreover, the reduction of the Mg content of MgxZn1−xO:Cu,N films led to an increase in the residual electron concentrations and contributed to the n-type conductivity.