Systems and methods for nanowire growth

A method for axially doping one or more desired portions of a nanowire along a length of the nanowire during growth of said nanowire comprising:

• (a) providing a substrate material having one or more nucleating particles deposited thereon in a reaction chamber;
• (b) contacting the nucleating particles with at least one precursor gas to initiate nanowire growth;
• (c) introducing at least one dopant gas into the reaction chamber during said nanowire growth to dope said one or more desired portions of the nanowire;
• (d) during and/or prior to said dopant introduction, introducing a non-precursor etchant gas into the reaction chamber at a certain pressure, wherein the etchant gas at the certain pressure is capable of substantially minimizing uncatalysed growth resulting from the at least one precursor gas on a sidewall of the nanowire during said nanowire growth and hindering incorporation of the at least one dopant on a sidewall of the nanowire;
• and
• (e) controlling the amount of said introduced non-precursor etchant gas to aid in axial dopant modulation of the nanowire.

A method for axial doping modulation of a nanowire during growth of said nanowire comprising:

• (a) providing a substrate material having one or more nucleating particles deposited thereon in a reaction chamber;
• (b) contacting the nucleating particles with at least one precursor gas to initiate nanowire growth;
• (c) intermittently introducing at least one dopant as into the reaction chamber during said nanowire growth to axially modulate the nanowire doping;
• and
• (d) introducing a non-precursor etchant gas into the reaction chamber during step (c), wherein the etchant gas is capable of hindering incorporation of the at least one dopant on a sidewall of the nanowire, wherein the non-precursor etchant gas is introduced at a relatively low pressure compared to the pressure of the at least one precursor gas.

A method for axial doping modulation of a nanowire during growth of said nanowire comprising:

• (a) providing a substrate material having one or more nucleating particles deposited thereon in a reaction chamber;
• (b) contacting the nucleating particles with at least one precursor gas to initiate nanowire growth;
• (c) intermittently introducing at least one dopant gas into the reaction chamber during said nanowire growth to modulate the nanowire doping;
• (d) introducing a non-precursor etchant, gas into the reaction chamber during step (c), wherein the etchant gas is capable of hindering incorporation of the at least one dopant on a sidewall of the nanowire;
• and
• (e) controlling the amount of the etchant gas introduced in step (d) depending on the dopant gas to hinder incorporation of the dopant on a sidewall of the nanowire during said axial modulation of the nanowire doping.