BeCaZnO quaternary alloy: thin films and ultraviolet photodetectors

Abstract

Enlightened by the quaternary alloy of BeMgZnO, we attempted the first study of BeCaZnO quaternary alloy in this work. We succeeded in the growth of single-phase BeCaZnO alloy films by pulsed laser deposition, and developed planar photoconductive-type ultraviolet (UV) photodetectors using BeCaZnO as the active layer. The structure, morphology, and optical bandgap of the alloy films were studied as a function of the substrate temperature, which revealed 525 °C as the suitable growth temperature. BeCaZnO-based photodetectors were then fabricated and systematically investigated using current-voltage, spectral photoresponse, and time-dependent photoresponse characterizations. At a bias voltage of 5 V, the device based on BeCaZnO film grown at 525 °C showed a low dark current of 0.49 nA with a cut-off wavelength at ∼400 nm. The peak responsivity of the device was 0.34 A/W located around 330 nm, and the specific detectivity approached 1.53 × 1011 cm∙Hz1/2/W (Jones). Compared with ZnO-based photodetectors, the BeCaZnO photodetectors possessed a significantly lower dark current and faster photoresponse speed. Our work indicates that BeCaZnO alloys are highly promising for future applications in optoelectronic devices such as UV photodetectors.