Research On Transparent N/P Type Semiconductor Thin Film Transistors

Thin film transistors(TFTs)are the core components of the new panel display technology.With the continuous innovation and breakthrough of display technology,the performance requirements of TFTs are also increasing.Silicon-based TFTs have been unable to meet the needs of the market.Oxide thin film transistors are widely used in the flat panel display industry due to their advantages of transparency,low cost,low temperature process and high mobility.ZnO-TFTs have excellent electrical properties,low cost,no pollution,and visible light transparency,making them one of the most promising n-type devices for transparent electronics.However,the stability of ZnO-TFTs has become an important factor that restricts its practical application.In this article,the ZnO film was grown by atomic layer deposition(ALD).The effects of precursor dose and growth temperature during ZnO growth on the properties of ZnO-TFTs during ZnO growth were studied.The optimal preparation process was determined.The device has excellent electrical properties:carrier saturation mobility of up to 36.4 cm2/Vs,switching ratio of 2.86x109,and turn-on voltage of-0.98 V.Secondly,and stability of the device were systematically tested and analyzed,including:bias voltage stability,photosensitivity,repeatability and uniformity.The ZnO-TFTs prepared by our process exhibit small shifts in threshold voltages such as positive gate bias stress,negative gate bias stress,hot carrier stress,and self-heating stess,and exhibit high stability.The transfer characteristic test is carried out 1500 times in succession,and the voltage offset change does not exceed 0.1 V,and the device also resists the influence of moisture and oxygen in the air.The electrical properties of the devices prepared in different batches or in the same batch are also similar,which ensures the yield of ZnO-TFTs is also very good.The counters based on ZnO-TFTs also have good stability.The output frequency curve is still not offset when running continuously for 15000 s.The research content of this part lays the foundation for the practical application of ZnO-TFTs.We have prepared high performance and stable ZnO-TFTs.In a series of research work,we fully realize that although all N-type integrated circuits can achieve certain basic functions,to further improve circuit performance,CMOS circuits are essential.That is to say,it is necessary to have stable N-type and P-type thin film transistors at the same time.Cuprous iodide(y-Cul)is an intrinsic P-type semiconductor with a band gap of 3.1 ev.Compared with other P-type semiconductors,cuprous iodide has the advantages of low growth temperature,high Hall mobility,and transparent film visible light,become our preferred P-type semiconductor material.Referring to the growth mode of several Cul,the thermal evaporation method was chosen by us.The transparent Cul film was prepared by thermal evaporation method,and the electrical properties of films were tested.Secondly,the effect of annealing temperature on the conductivity and Hall mobility of cuprous iodide film was studied.The transparent Cul film was prepared by thermal evaporation method,and the electrical properties of the film were tested.Secondly,the influence of the subsequent inert gas annealing temperature on the electrical conductivity and Hall mobility of the cuprous iodide film was studied.On this basis,the preparation process of heterojunction based on P-CuI/N-ZnO and the fabrication process of CuI-TFTs were explored.The PN junction has a preliminary rectification effect,and the rectification ratio has reached 103.The CuI-TFTs we have prepared have exhibited P-type device characteristics,but the voltage of the device near OV is difficult to turn off,which need to be optimized.