Characterization of nanowire light-emitting diodes grown by selective-area metal-organic vapor-phase epitaxy

Abstract

We report a systematic study on the current injection and radiative carrier recombination in InP nanowire (NW) light-emitting diodes (LEDs). The InP NWs with axial p-n structures, grown by selective-area metal organic vapor-phase epitaxy, had mixed crystal structures between those of zincblende and wurtzite, mainly in the p-regions. The temperature dependence of the currentvoltage (I-V ), electroluminescence (EL), and current-light output (I-L) characteristics was investigated. The temperature dependence of the I-V characteristics revealed that tunneling was the main mechanism of carrier transport through the p-n junction in the present NW-LEDs. The temperature and bias voltage dependences of EL showed a complex but systematic behavior, where peaks exhibiting bias-dependent and independent energy positions coexisted and the relative intensity showed a transition with increasing temperature. The external quantum efficiency showed a droop at low temperatures, indicating a reduced injection efficiency at low temperatures. These observations were explained by the radiative and nonradiative tunneling, and suggested a strong effect of the nonradiative tunneling at low temperatures.

n‐Doped InGaP Nanowire Shells in GaAs/InGaP Core–Shell p–n Junctions

“…To further substantiate the assumed tunneling processes, low‐temperature EL measurements with varying bias are conducted at a fixed temperature T = 79 K. The resulting spectra are displayed in Figure b. As previously observed for radiative tunneling processes in abrupt p–n‐homojunctions, the maximum peak intensities shift to higher energies with increasing excitation current, and the low‐energy side of the spectrum is saturated while the peak itself broadens with rising current . The observed sub‐band gap EL at low temperatures and its shift with applied bias are strong indications for dominant radiative tunneling currents through the p–n‐heterojunction under forward bias.…”

“…Simultaneously, underlying peaks at the low‐energy side increase in intensity and shift to lower energies. Pronounced sub‐bandgap EL has been observed in heavily doped GaAs p–n‐homojunctions in layers and axial NWs and was reported in compositionally graded planar GaAs/AlGaAs heterojunctions previously . This luminescence is linked to radiative tunneling mechanisms, such as band‐filling or photon‐assisted tunneling.…”

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

“…[2] The synthetic approaches control their composition, size and electronic structure (energy levels, density of states within the bands and in the bandgap) and the charge-carrier transport. For this reason, nanowires and nanotubes are particularly attractive in nanoelectronics and optoelectronics as functional interconnects, building blocks of nanotransistors, [4,5] light-emitting diodes [6] or detectors of radiation. Its great importance stems from the fact that it is a noncontact method and, owing to its high frequency and broadband character, it is capable of characterizing charge transport properties within individual nano-objects but also among them.…”

“…Terahertz Conductivity Spectra Dr. P. Kužel the advantages of small size and efficient charge transport along the axial direction. For this reason, nanowires and nanotubes are particularly attractive in nanoelectronics and optoelectronics as functional interconnects, building blocks of nanotransistors, [4,5] light-emitting diodes [6] or detectors of radiation. [7,8] The dimensions can be pushed further down toward the molecular level.…”

Tunneling‐Related Leakage Currents in Coaxial GaAs/InGaP Nanowire Heterojunction Bipolar Transistors

“…The transfer of the properties of modulation‐doped compound semiconductor homo‐ and heterostructures with charge‐separating pn‐junctions into nanowire (NW) device topologies is of profound interest as NWs can be considered to serve as low‐cost, versatile building blocks for future electronic and optoelectronic applications. [ 1–3 ] A multitude of benefits stemming from the NW's small dimensions and high aspect ratio in combination with the optical and electronic properties of the III–V material system have already been demonstrated in pn‐based NW devices such as light emitting diodes (LEDs), [ 3–10 ] solar cells, [ 3,11–14 ] photodetectors, [ 3,15,16 ] and optically pumped lasers. [ 17,18 ] Utilizing compound semiconductor heterostructures in pn‐junctions allows for device designs with enhanced functionalities.…”