Research On Doping And Radial Pn Junction Of Gallium Arsenide Nanowire

Semiconductor nanowires are ideal building blocks for functional nanoscale device and have been investigated extensively over the past few years. By now, nanowires from not noly group IV elements, but also III-V and II-VI compound semiconductors have been realized, including variation of composition and doping along their length. Among which, III-V semiconductor nanowires excite great research interest due to their direct and tunable band gap. GaAs is of significant interest for device applications because it possesses an intrinsically high electron mobility while controllable doping and pn-junction synthesis in a single nanowire is the key factor of device fabrication. In this paper, I research on GaAs nanowire doping and synthesis of radial pn-junction in a single GaAs nanowire. The main achievements are listed as follows:1. The research results of GaAs nanowire doping by foreign laboratories are studied, the dopants and common ways in GaAs nanowire doping are compared.2. The nanowire pn-junction width is modeled and simulated. The result shows the pn-junction width decreases by increasing the inflow flux of the first dopant or decreasing the inflow flux of the second dopant.3. P-type and n-type GaAs nanowires are grown on GaAs (111)B substrate by MOCVD via Au-catalyzed vapor-liquid-solid mechanism, using DEZn as p-type dopant and SiH4 as n-type dopant respectively. The experiment result shows that large DEZn flux(Ⅱ/Ⅲ>0.08%) will lead to nanowires’kinking and deformation. It is the same as the foreign laboratories reported. As the acceptor concentration NA is proportional to the II/III ratio, there exists a limit for p-type doping level. Because Si has no remarkable effect on nanowires’morphology, the experiment result shows that the nanowires are perpendicular to the substrate and uniform in diameter even under large SiH4 inflow flux(80sccm),4. Using MOCVD growth technology, two types of nanowire p-n junctions were fabricated by growing an n(p)-doped GaAs shell outside a p(n) GaAs core on p(n)-type GaAs(111)B substrate. The morphology, crystal structure and doping characteristics of samples under different DEZn inflow flux(10,40,70sccm) were investigated by FESEM, TEM and EDS. The result shows that radial pn-junction GaAs nanowire can tolerate much higherⅡ/Ⅲratio than that of axial ones. The p-type doping level is expected to be higher than the axial pn-junction GaAs nanowires due to the largerⅡ/Ⅲratio. The EDS analysis shows that both of the dopants were successfully incorporated into the nanowires and the result was in good agreement of the doping type on the investigated samples.5. The electrode post-craft disposal on radial pn-junction GaAs nanowires is processed and the morphology of the sample nanowires are investigated. The result shows that some nanowires gather and tilt slightly. It mainly meet the requirement of the electrode fabricating.