Large ferro-pyro-phototronic effect in 0.5Ba(Zr_(0.2)Ti_(0.8))O_(3)-0.5(Ba_(0.7)Ca_(0.3))TiO_(3)thin films integrated on silicon for photodetection

Coupling together the ferroelectric,pyroelectric,and photovoltaic characteristics within a single material is a novel way to improve the performance of photodetectors.In this work,we take advantage of the triple multifunctionality shown by 0.5Ba(Zr_(0.2)Ti_(0.8))O_(3)-0.5(Ba_(0.7)Ca_(0.3))TiO_(3)(BCZT),as demonstrated in an Al/Si/SiOx/BCZT/ITO thin-film device.The Si/SiOx acts as an n-type layer to form a metal-ferroelectric-insulator-semiconductor heterostructure with the BCZT,and with Al and ITO as electrodes.The photo-response of the device,with excitation from a violet laser(405 nm wavelength),is carefully investigated,and it is shown that the photodetector performance is invariant with the chopper frequency owing to the pyro-phototronic effect,which corresponds to the coupling together of the pyroelectric and photovoltaic responses.However,the photodetector performance was significantly better than that of the devices operating based only on the pyro-phototronic effect by a factor of 4,due to the presence of ferroelectricity in the system.Thus,after a poling voltage of−15 V,for a laser power density of 230mW/cm^(2)and at a chopper frequency of 400Hz,optimized responsivity,detectivity,and sensitivity values of 13.1mA/W,1.7×10^(10)Jones,and 26.9,respectively,are achieved.Furthermore,ultrafast rise and fall times of 2.4 and 1.5μs,respectively,are obtained,which are 35,000 and 36,000 times faster rise and fall responses,respectively,than previous reports of devices with the ferro-pyro-phototronic effect.This is understood based on the much faster ferroelectric switching in ferroelectric thin films owing to the predominant 180°domains in a single direction out of plane.