Coaxial Circular Test Structure Applicable to both Ohmic and Schottky Characteristics for ZnO/Si Heterojunctions Assessment

Characterizing junction is essential in new devices research. We are investigating a hybrid infrared-sensitive opto-electronic device on silicon-based large scale integrated circuits, among others, PbS colloidal quantum dots/ZnO/Si hybrid IR detector. To assess such new materials we propose a coaxial circular test structure. The structure is composed of common-central inner (circular) and outer (doughnut) electrodes. In addition to traditional Circular TLM (CTLM) test structure, which was used for ohmic contact, the junction type (ohmic or Schottky) can be identified and quantitatively be analyzed by measuring various gaps and surface areas of the proposed structure (Coaxial CTLM, CCTLM). The measurement using test structure on our n-type ZnO / n-type Si heterojunction sample revealed that the junction was Schottky type, which was opposite to our expectation.