The Study On The Application Of Indium Gallium Zinc Oxide Interlayer In Nonvolatile Pentacene Organic Field-effect Transistor Memory Devices

As the carrier of information storage,memory has always been an indispensable part of electronic equipment.Inorganic flash memory with charge trapping dielectric occupies the majority of the storage-device market.But with the continuous development of semiconductor manufacturing technology,inorganic flash memory devices gradually approach the physical limit,and will not be able to meet the increasing needs of storage devices.On the other hand,the development of organic semiconductors provides another brand-new possibility for semiconductors.After the development for more than half a century,more and more organic semiconductors have been used in different fields,organic memory based on organic electronics is one of the very important research fields.As a very important organic memory,the OFET nonvolatile memory with polymer electret as the charge-trapping layer has attracted widespread attention.Because it has a lot of advantages such as large storage window,the device structure and the preparation process is simple,low cost and large area printing preparation,it shows a good prospect of application in the radio frequency identification tags,flexible and large area display.etc.Pentacene is a kind of organic semiconductor with high mobility and stable chemical properties,so it is widely used in OFET devices.However,the operating voltage of the existing pentacene OFET memory device is often as high as hundreds of volts,which is far from the actual standard of modern electronic device application.The programing/erasing pulse time of the device is often dozens of seconds,and the programing/erasing speed needs to be improved.In addition,the number of effective programing/erasing operation of the device is also lower.These shortcomings seriously limit the application of pentacene OFET memory devices.Both theoretical and experimental studies have shown that there are positively charged defects associated with the external environment(e.g.,hydrogen and oxygen)at the boundary of pentacene near the interface of pentacene/polymer.The thickness of the positively charged defect layer is about 1.5 nm.Due to the defects,the thin layer is no longer of semiconductor characteristics.The electric field formed by the positive charges in thin layer points to p-type semiconductor pentacene,and impedes the transfer of holes from pentacene to polymer.The positively charged defects act as a positivecharge barrier layer,which results in the high working voltage of pentacene OFETs using polymer films as charge trapping dielectric.In this work,we propose a new IGZO intercalated pentacene OFET nonvolatile memory device on the basis of the existing research.Then fabricated the pentacene OFET nonvolatile memory devices with different thickness of IGZO film and different carrier concentration in IGZO film,and analyzed the effect on the memory performance of the device.The main results are summarized as follows:1.Design a new kind of OFET non-volatile memory device: An IGZO n-type semiconductor thin film was set between the insulating layer and the polymer electret in the OFET memory devices with the structure of gate-electrode/insulating layer/polymer/pentacene/source(drain)electrode.The induced electrons at the interface of IGZO film and polymer electret lead to the reduction of the height of the hole-barrier formed at the interface of polymer and pentacene,thus effectively reducing the programming/erasing (P/E)gate voltages of pentacene OFET memory device.2.The nonvolatile pentacene OFET memory devices with different thickness of IGZO intercalators were fabricated.The experimental results show that the IGZO interlayer can make the memory windows of the device larger,the P/E speed faster,and the operating voltage lower.And with the increase of the thickness of IGZO interlayer,the memory windows of the device are larger,but the retention performance of the device decays obviously.The results verified that the potential barrier of pentacene /PVN interface would decrease significantly due to the IGZO interlayer,and the thicker the IGZO interlayer,the more the potential barrier of pentacene /PVN interface would decrease,which was consistent with the device design expectation.3.The nonvolatile pentacene OFET memory devices with different carrier concentration in IGZO interlayer was fabricated.The experimental results further show that the IGZO interlayer can make the memory windows of the device larger,the P/E speed faster,and the operating voltage lower.And with the increase of IGZO carrier concentration,the memory windows of the device become larger,but the retention characteristic of the device decays obviously.This result effectively verified the effect of IGZO intercalation on the significant decrease of the barrier height at the interface of pentacene/PVN again,and the higher the IGZO intercalation concentration,the more the potential barrier decrease at the pentacene /PVN interface.