MoGe Josephson junctions

We have fabricated and characterized MoGe/Al/AlO_x/(Al)MoGe Josephson junctions (JJs) using amorphous MoGe thin films with superconducting transition temperatures up to 7 K. Amorphous MoGe films are known to have very smooth and uniform surfaces, which allows us to achieve high quality tunnel barriers and excellent uniformity of the junction properties when using a very thin Al overlayer to form the barrier. Our experimental results and comparisons with the theoretical calculations confirm these behaviors. High uniformity of the characteristics of the MoGe junctions, which exceeds that of Nb/Al/AlO_x/(Al)/Nb junctions fabricated using the same equipment, is important for practical applications involving superconducting electronics. In particular, we suggest that MoGe junctions are especially suitable for applications where vertical stacking of multiple JJs is desirable, e.g., in voltage standards and Josephson oscillators. Exploiting these junctions in qubits is also expected.