No abstract

The use of tetraethyltin (TESn) and dimethylzinc (DMZn) as in situ n- and p-dopant precursors during particle-assisted growth of InP nanowires is reported. Gate voltage dependent transport measurements demonstrate that the nanowires can be predictably synthesized as either n- or p-type. These doped nanowires can be characterized based on their electric field response and we find that n-type doping scales over a range from 10(17) to 10(19) cm(-3) with increasing input TESn dopant molar fraction. On the other hand, the p-type doping using DMZn saturates at low levels, probably related to a strong increase in nanowire growth rate with increasing DMZn molar fractions. By optimizing growth conditions with respect to tapering, axial pn-junctions exhibiting rectifying behavior were fabricated. The pn-junctions can be operated as light emitting diodes.

Tandem InP nanowire pn-junctions have been grown on a Si substrate using metal-organic vapor phase epitaxy. In situ HCl etching allowed the different subcomponents to be stacked on top of each other in the axial extension of the nanowires without detrimental radial growth. Electro-optical measurements on a single nanowire tandem pn-junction device show an open-circuit voltage of 1.15 V under illumination close to 1 sun, which is an increase of 67% compared to a single pn-junction device.

We have investigated p-doping of InP nanowires using diethyl zinc. Two-terminal devices showed non-linear source-drain characteristics and p-type gate dependence. Electron beam induced current measurements were employed to determine minority carrier diffusion lengths. We used large-area tunnel diodes to demonstrate degenerate doping, showing peak current densities of up to 0.11 A/cm2 and room temperature peak to valley current ratios of 5.3. These results demonstrate that high p- and n-doping, paired with sharp doping profiles, can be achieved in InP nanowires.