Abstract: An example method of forming a photonic device is described herein. The method can include providing a flexible polycrystalline substrate, and growing a nanowire heterostructure on the flexible polycrystalline substrate. Optionally, the method can further include fabricating a light emitting diode (LED), a photodiode, a laser, a solar cell, or a photocatalytic water splitter with the nanowire heterostructure.

Abstract: A nanowire comprises a polar semiconductor material that is compositionally graded along the nanowire from a first end to a second end to define a polarization doping profile along the nanowire from the first end to the second end. The polar semiconductor material may comprise a group IH-nitride semiconductor, such as an alloy of GaN and AlN, or an alloy of GaN and InN. Such nanowires may be formed by nucleating the first ends on a substrate, growing the nanowires by depositing polar semiconductor material on the nucleated first ends on a selected growth face, and compositionally grading the nanowires during growth to impart the polarization doping. The direction of the compositional grading may be reversed during the growing of the nanowires to reverse the type of the imparted polarization doping. In some embodiments, the reversing forms n/p or p/n junctions in the nanowires.

Abstract: A diode comprises nanowires compositionally graded along their lengths with an active region doped with gadolinium sandwiched between first and second compositionally graded AlxGa1-xN nanowire regions. The first graded AlxGa1-xN nanowire region is graded from gallium-rich to aluminum-rich with the compositional grading defining n-type polarization doping and the aluminum-rich end proximate the active region. The second graded AlxGa1-xN nanowire region is graded from aluminum-rich to gallium-rich with the compositional grading defining p-type polarization doping and with the aluminum rich end proximate the active region. The active region may include a GdN layer sandwiched between AlN layers, or an Al1-yGdyN layer with y?0.5.

Abstract: A diode comprises nanowires compositionally graded along their lengths with an active region doped with gadolinium sandwiched between first and second compositionally graded AlxGa1-xN nanowire regions. The first graded AlxGa1-xN nanowire region is graded from gallium-rich to aluminum-rich with the compositional grading defining n-type polarization doping and the aluminum-rich end proximate the active region. The second graded AlxGa1-xN nanowire region is graded from aluminum-rich to gallium-rich with the compositional grading defining p-type polarization doping and with the aluminum rich end proximate the active region. The active region may include a GdN layer sandwiched between AlN layers, or an Al1-yGdyN layer with y?0.5.

Abstract: A position sensor comprises a group III-nitride Hall effect sensor arranged to measure magnetic field from a magnet wherein the group III-nitride Hall effect sensor and the magnet are arranged to move relative to one another in response to movement of an element whose motion is to be monitored. The electrically conductive layer of the group III-nitride Hall effect sensor may comprise a two-dimensional electron gas (2DEG) defined by an AlxGa1-xN/GaN interface where x>0 and in some embodiments x=1 (i.e. an A1N/GaN interface). Disclosed position measurement methods comprise measuring position or speed of the element being monitored using such a position sensor in an environment at a temperature of at least 300° C., and in some embodiments at least 350° C.

Abstract: A nanowire comprises a polar semiconductor material that is compositionally graded along the nanowire from a first end to a second end to define a polarization doping profile along the nanowire from the first end to the second end. The polar semiconductor material may comprise a group IH-nitride semiconductor, such as an alloy of GaN and AlN, or an alloy of GaN and InN. Such nanowires may be formed by nucleating the first ends on a substrate, growing the nanowires by depositing polar semiconductor material on the nucleated first ends on a selected growth face, and compositionally grading the nanowires during growth to impart the polarization doping. The direction of the compositional grading may be reversed during the growing of the nanowires to reverse the type of the imparted polarization doping. In some embodiments, the reversing forms n/p or p/n junctions in the nanowires.