| As an important semiconductor electronic components,diodes have a wide range of ap-plications in microelectronics and optoelectronics.Traditional silicon diode devices with low mobility and high threshold voltage limit their use in high frequency applications and where low on-state bias voltage is required.And,as the diode size shrinks,its device performance and processing levels are close to the theoretical limits.Therefore,the adoption of ideal materials and excellent device structures is highly desirable for making high-performance diodes.Among nanomaterials,semiconductor single wall carbon nanotubes(SWNTs)has a unique structure and excellent performance,is expected to be used to make high-performance diode in place of or in addition to some of the silicon-based diodes.Compared to the traditional silicon diode,SWNT diode has higher device performance,lower power consumption and smaller device size.The paper proposes two new SWNT diodes based on asymmetric Schottky junctions and p-i-n junctions.In the asymmetric Schottky junction SWNT diode,Pd and Al contacts were fabricated on opposite ends of a single SWNT to form p-type and n-type Schottky contacts,respectively,resulting in a strong built-in electric field within the SWNT.In the p-i-n junction SWNT diode,the opposite ends of the individual SWNT channels were doped selectively by triethyloxonium hexachloroantimonate(OA)and polyethylene imine(PEI)to obtain stable p-and n-type SWNT segments respectively,while the middle segment of the SWNT was kept intrinsic,causing the formation of an intra-tube p-i-n junction.Structure design,key production technology,device characteristics and working principle for these two kinds of device were conducted in-depth systematic research in this paper.First,the paper innovatively develops a Schottky junction diode with a high work function metal/SWNT/low work function metal structure.We used the high work function metal Pd and the low work function metal Al as contact metals to investigate their contact characteristics with SWNTs.Studies have shown that they can form p-type and n-type Schottky contacts with SWNTs,respectively.Using this characteristic,a Pd/SWNT/Al asymmetric metal-contact Schottky junction diode was fabricated by contacting Pd and Al with SWNT at opposite ends.Under gate voltage regulation,the device exhibits good rectification characteristics with a rec-tification ratio of up to 103.Secondly,the thesis proposes and develops a SWNT p-i-n junction diode based on local selective doping.Long-term stable p-type and n-type doping of SWNTs was achieved by using triethyloxonium hexachloroantimonate(OA)as a p-type dopant and polyethylenimine(PEI)as an n-type dopant.Doping SWNTs film and single SWNT in device were investigated.It is shown that OA and PEI can effectively doping SWNTs into p-type and n-type,respectively.Using this feature,we use OA and PEI to selective dope the opposite sides of the SWNT channel,while the middle section of the SWNT is protected by the PMMA to maintain the intrinsic state,thereby successfully achieved SWNT intramolecular p-i-n junctionin diode.The presence of intrinsic region(i region)favor the formation of a strong internal electric field in the entire SWNT,thereby improving the rectifying characteristics of the devices,the rectification ratio of up to 1.2×103.In order to further improve output current and stability of the diode,the paper first studies p-i-n junction diode based on disordered network SWNT.An electrostatic self-assembly tech-nique was used to achieve a controlled production of a monolayer disordered SWNT network.The resulting diode can be greater output current,up to milliampere level.This disordered SWNT network p-i-n junction diode delivers a current of 12.2μA at a forward bias of 1V while achieving a rectification ratio of up to～1.3×10~4.Based on this,the photovoltaic characteristics of SWNT p-i-n junction diodes were studied.Photovoltaic performance of p-i-n junction SWNT diode devices based on local selection doping was measured using a 1550 nm laser.The photovoltaic device exhibited a high open circuit voltage of 0.36 V and a power conversion efficiency of 3.9%.The research on SWNT diode based on asymmetric Schottky junction and p-i-n junction not only has far-reaching theoretical significance,but also provides a new direction for the ap-plication of SWNT.The research shows its great potential in the field of photovoltaics.It also has a wide range of applications in the fields of high-frequency signal processing,high-speed microelectronic circuits,optoelectronic devices and sensors. |
