Quasi-one Dimensional P-type ZnSe Nanostructure With Controlled Doping And The Heterojunctions Devices

ZnSe is an important II–VI compound semiconductor with wide direct band-gap of².70eV at room temperature. Due to their excellent optical and optoelectronic properties,it is regarded as one of most promising materials for optoelectronic applications, includinglight emitting diodes, photovoltaics, photodetector and so on. But ZnSe nanostructureusually suffer from the serious self-compensation effect, as a result, most of them showunipolar conduction behavior, i.e., only n-or p-type doping could be achieved. To date,p-type doping in ZnSe nanostructures has been accomplished by substituting Se2-ions withgroup V elements such as boron （B） and phosphorus （P），but it always suffer from lowconductivity and controllability. The synthesis of quasi one-dimensional ZnSenanostructures with controlled p-type doping and nanoscale devices is in great need.Silicon is of special interest due to its key role in the modern semiconductor industry.Nevertheless, the low emission efficiency caused by the indirect bandgap obstructs itsapplications in light emission devices. By combining it with ZnSe nanostructures, ZnSe/Sinano-heterostructures may offer an alternative way to realize Si-based optoelectronicintegration. The research of ZnSe nanostructures with controlled p-type doping and theZnSe/Si nano-heterostructures is significant.Here we accomplished p-type ZnSe nanowires （NWs） by using silver sulfide （Ag₂S）as the p-type dopant via a thermal evaporation method, and a host of ZnSe/Sinano-heterostructures based on it were also fabricated. The main achievements in our jobare as following:（1） The p-type ZnSe nanowires （NWs） has been accomplished by using silver sulfide（Ag₂S） as the p-type dopant via a thermal evaporation method. The results reveals that theZnSe:Ag NWs are clean and uniform with diameter in the range of50-300nm and lengthfrom tens of micrometers up to hundreds of micrometers, and NWs are zinc blende singlecrystals with [111] growth orientation.（2） The conductivities of the NWs could be tuned in9orders of magnitude byadjusting the Ag doping levels. Field-effect transistors （FETs） constructed from theZnSe:Ag NWs verified their p-type nature with a hole concentration up to2.1×10¹⁹cm^-3.Schottky barrier diodes （SBDs） based on the ZnSe:Ag NW/ITO junctions exhibitedremarkable rectifying behaviors with a rectification ratio>10⁷and a small ideality factor of ¹.29at320K.（3） The heterojunctions devices based on p-type ZnSe:Ag NW array/n-type Si werefabricated by three different ways.a) The heterojunctions devices was fabricated by parallelly aligning the p-typeZnSe:Ag NWs on n-Si substrate via a contact printing method, and thenpolymethylmethacrylate （PMMA） with thickness of²00nm was spin-coated on thesubstrate as the insulator layer. It exhibited remarkable photovoltaic characteristics with alarge fill factor （FF） of61%and a power conversion efficiency of¹.04%.b) The heterojunctions devices was fabricated by growing p-type ZnSe:Ag nanowireson n-type Si substrate. The heterojunction shows excellent stability and reproducibility towhite light irradiation with a fast response time （<0.1s） and a high Ilight/Idarkratio （>10³）.And the photovoltaic characteristics of it exhibit a fill factor of about24%and a highpower conversion efficiency of0.89%.c) ZnSe/Si core/shell nanowires were successfully produced by a simple two-stepgrowth method, and the p-n junction were fabricated based on the nanowires. Exceptremarkable rectifying behaviors, the p-n junction also shows excellent memorycharacteristics, with a resistance on/off ratio exceeding five orders of magnitude, a longretention time of over18h.