Process Optimization Of The Absorption Layer And Interface Of Cu₂Cd_xZn_(1-x)SnSe₄ Based Short-wave Infrared Detector

Short-wave infrared detectors have the advantages of strong atmospheric penetration,high image quality and resolution,and little environmental impact,which leads to great application potential and development prospects in the field of consumer electronics.At present,the commercial Hg Cd Te-type detectors with a huge equipment system,need to be operated in a low temperature environment.For In Ga As-type detectors,it's manufacturing process involves complicated epitaxial growth and undercut welding processes.Furthermore,the low yield rate makes the price staying at a high level.The above-mentioned devices are difficult to satisfy the application requirements of high-volume consumer electronic products.In contrast,the copper-based multi-element compound material Cu₂Cd_xZn_(1-x)Sn Se₄ proposed by our laboratory considered to be an important material for making low-cost infrared detectors.It has the advantages of adjustable band gap(0.78?1.3 e V),low cost of raw material,simple preparation process,easy integration with integrated circuits and large-scale production.However,the Cu₂Cd_xZn_(1-x)Sn Se₄ based infrared detectors still have the problems of high dark current and low detectivity,which are two major problems that need to be solved urgently as a detector.In response to these issues,this article has carried out the following series of research work:1.Obtaining high-quality crystalline of absorption layer is the key to improving the performance of the detectors.The Se annealing process is used to control the carrier concentration and defect of the absorption material.Se-annealing process at different temperatures was performed on the absorb film,and it was found that the higher the annealing temperature,the better the crystallinity of the CCZTSe absorption layer,and the better the grain size and uniformity.At the annealing temperature of 540?,the Sn Se₂ impurity in the film decreased.However,the excessively high temperature causes serious loss of Sn elements,resulting in a large number of holes in the film,which reduces the photoelectric conversion efficiency of the detector.The devices with better performance among the fabricated devices were fabricated at 510?,with the dark current is 126?A/cm²,and the EQE is maintained at 30-40%in the 400-1400 nm.2.Different annealing heating rates was applied to the absorption layer.And shows that the faster the heating rate,the easier to form flake-shaped Sn Se₂,which leads to the heterogeneity of component,brings to the EQE drops in infrared light.While the heating rate slows down,Sn Se₂ will continue to participate in the reaction and be absorbed into the CCZTSe,but it will also cause the loss of Sn.When the annealing time is 60 min,the device perform well,with the dark current is 73?A/cm²,and the EQE is stable at about 40%in the 400-1400 nm.3.Reducing the defect state of the crystal interface of the absorber layer is a common method to improve the performance of the device.Atomic layer deposition method(ALD)was used to grow Al₂O₃ barrier layers with different thicknesses on the surface of the annealed absorber layer in order to reduce the dark current and improve detectivity of the devices.When the thickness of the barrier layer is 7 nm,the dark current of the device is reduced by nearly two orders of magnitude,and the switching of the device is two orders of magnitude higher than that of I_light/I_dark.4.Performing the H₂S post-anneal passivation process on the absorber layer,passivate the absorption layer interface to remove the dangling bonds,thereby reducing the density of states and reducing the photoelectric loss.As the concentration of H₂S increases,the detectivity of the device has a tendency to increase first and then decrease,due to the high H₂S concentration causing a high-resistance layer on the surface,which affects the performance of the device.In summary,this article focuses on the selenization annealing process and crystal interface passivation process of Cu₂Cd_xZn_(1-x)Sn Se₄ absorption layer,and the relevant process parameters for the preparation of high-performance near-infrared detectors are obtained.