Co-doping approach for p-type ZnO with combinatorial laser MBE method

We show here three different ways of combinatorial experiments for achieving precise control of dopant concentration in ZnO thin films. Alternating ablation of highly pure single crystal target and ceramics target doped with concentrated Ga dopant yielded in a systematic control of Ga concentration with keeping minimal contamination of undesired impurity. Secondary ion mass spectroscopy for a stack of several ZnO films grown at different temperatures under a constant exposure of N radical gave us a systematic calibration curve for the N concentration. With using a special heating method to give a controlled temperature gradient on a substrate, we demonstrate that continuous spread of N concentration can be built in a film on a substrate with keeping constant Ga concentration. Such systematic experiments taking into account the "combinatorial" concept enable us to make ZnO films with controlled dopant concentrations.