Measurement of the zinc oxide–molybdenum specific contact resistance for applications in Cu(In,Ga)Se2-technology

We developed an improved measuring structure based on the transmission line model (TLM) which allows us to determine the specific contact resistance between rf-sputtered aluminum doped zinc oxide (ZnO:Al) and dc-sputtered molybdenum despite inhomogeneities in film thickness and conductivity which normally prevent an accurate determination of this value with the TLM. The improvement was achieved by an interchange between the contact and the conduction bar material to get a lower resistance of the conduction bar. Using this structure, the specific contact resistance is ascertained to be (1.37 ± 0.14) × 10− 5 Ω cm2. In addition, the effects of variations of certain sputter deposition parameters and their influence on the specific contact resistance are demonstrated. In particular, a small amount of oxygen in the sputter gas during the molybdenum sputter process remarkably increases the specific contact resistance.