Fast and Uncooled Semiconducting Ca-Doped Y-Ba-Cu-O Thin Film-Based Thermal Sensors for Infrared

• Published in: Sensors (Basel, Switzerland) Vol. 23; no. 18; p. 7934
• Main Authors: Dégardin, Annick, Alamarguy, David, Brézard Oudot, Aurore, Beldi, Samir, Chaumont, Christine, Boussaha, Faouzi, Cheneau, Antoine, Kreisler, Alain
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.09.2023; MDPI
• Subjects: amorphous thin films; Bandwidths; calcium doping in Y-Ba-Cu-O; Engineering Sciences; Imaging systems; noise measurements; pyroelectric detectors; Quantum dots; Radiation; Scanning electron microscopy; Sensors; Thin films; uncooled near-infrared sensors; Y-Ba-Cu-O semiconductor; France
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s23187934

YBa2Cu3O6+x (YBCO) cuprates are semiconductive when oxygen depleted (x < 0.5). They can be used for uncooled thermal detection in the near-infrared: (i) low temperature deposition on silicon substrates, leading to an amorphous phase (a-YBCO); (ii) pyroelectric properties exploited in thermal detectors offering both low noise and fast response above 1 MHz. However, a-YBCO films exhibit a small direct current (DC) electrical conductivity, with strong non-linearity of current–voltage plots. Calcium doping is well known for improving the transport properties of oxygen-rich YBCO films (x > 0.7). In this paper, we consider the performances of pyroelectric detectors made from calcium-doped (10 at. %) and undoped a-YBCO films. First, the surface microstructure, composition, and DC electrical properties of a-Y0.9Ca0.1Ba2Cu3O6+x films were investigated; then devices were tested at 850 nm wavelength and results were analyzed with an analytical model. A lower DC conductivity was measured for the calcium-doped material, which exhibited a slightly rougher surface, with copper-rich precipitates. The calcium-doped device exhibited a higher specific detectivity (D*=7.5×107 cm·Hz/W at 100 kHz) than the undoped device. Moreover, a shorter thermal time constant (<8 ns) was inferred as compared to the undoped device and commercially available pyroelectric sensors, thus paving the way to significant improvements for fast infrared imaging applications.