Semiconducting Amorphous Y-Ba-Cu-O: An Attractive Material For Fast And Sensitive Thermal Sensing In The Nir To Thz Range

Since the observation of pyroelectric properties in oxygen depleted semiconducting Y-Ba-Cu-O, the interest of its amorphous phase (a-YBCO) obtained at low deposition temperature (150 degrees C) has been demonstrated for near-infrared (NIR) detection. At the core of the uncooled thermal detector development, there is the material choice for sensing the incoming radiation. Apart from its manufacturing compatibility with silicon technologies for further integration with readout electronics, a low noise level and a high value of the pyroelectric coefficient are highly desirable material properties. In the first part of this paper, we investigate room temperature noise performances of planar and trilayer detectors fabricated on silicon substrates. The best noise equivalent power (NEP) and detectivity D*, which are at the state of the art, were observed at 10 kHz modulation frequency: NEP = 2.0 pW/Hz(1/2) and D* = 6.6x10(9) cm.Hz(1/2)/W for planar structures; NEP = 2.6 pW/Hz(1/2) and D* = 5.7 x10(9) cm.Hz(1/2)/W for trilayers. These detectors also exhibit a very fast response (time constant tau = 1.9 mu s for planar, and tau = 0.12 mu s for trilayer devices) as compared to commercially available pyroelectric sensors. In the second part, we examine the pyroelectric response of a-YBCO to extract the pyroelectric coefficient p. A first estimate of p gave a value as high as 600 mu C.m(-2).K-1 at 300 K. The pyroelectric figure of merit F-d which takes into account dielectric properties of the material (dielectric constant and dielectric losses) is also discussed with respect to results published for pyroelectric oxide thin films sputtered on silicon substrates.