Amorphous semiconducting Y-Ba-Cu-O: a siliconcompatible material for IR uncooled sensitive detection with microsecond response time
Résumé
The yttrium-barium-copper oxide cuprate (YBCO) is well-known to exhibit superconducting properties in its YBa2Cu3O(6+x) phase for x close to 1. Oxygen depletion (x ≈ 0.3-0.5) of this compound leads, however, to a semiconductor. An unusual although promising application of YBCO in this semiconducting form can be sought in the field of uncooled thermal detectors of the bolometer type due to its large temperature coefficient of resistance (TCR = 1/R (dR/dT) = -3 to -4 %/K). Besides, semiconducting YBCO films can be deposited without substrate heating in amorphous semiconducting form (a-YBCO), which makes the integration of this material compatible with already processed signal readout electronics (e.g. a CMOS chip). In the present work, we consider two a-YBCO bolometric geometries, i.e. planar (#Si-pla) or trilayer (#Si-tri), and compare their detection performance with reference to already reported semiconducting devices, mainly designed for room temperature operation. For both detector devices, the response was measured at 850 nm wavelength for experimental convenience. The response of device #Si-pla exhibited a low-frequency regular low-pass bolometric behavior (30 Hz cut-off), followed by a high-pass behavior (60 kHz cut-off / 3 μs time constant) that could be assigned to the pyroelectric state of a-YBCO. The response of device #Si-tri exhibited the high-pass behavior only. Detectivity values up to 3.5×108 cm⋅Hz1/2⋅W−1 have been measured. The high frequency sensitivity offers a promising solution for fast imaging applications, especially in the far IR / THz range where moderate cost systems should be considered.