Single Quantum Dot Nanowire LEDs

Abstract

We report reproducible fabrication of InP-InAsP nanowire light emitting diodes in which electron-hole recombination is restricted to a quantum-dot-sized InAsP section. The nanowire geometry naturally self-aligns the quantum dot with the n-InP and p-InP ends of the wire, making these devices promising candidates for electrically-driven quantum optics experiments. We have investigated the operation of these nano-LEDs with a consistent series of experiments at room temperature and at 10 K, demonstrating the potential of this system for single photon applications.Nanowire light emitting diodes (NW LEDs) offer exciting new possibilities for opto-electronic devices. Growth of direct-bandgap NWs on Si 1, 2 will allow optically active elements to be integrated with already highly mature Si technology. For solid-state lighting applications, broad-area LEDs made from NW arrays have higher light-extraction efficiency than traditional planar LEDs 3 , and in the field of quantum optics, NWs offer the possibility to control electron transport at the single-electron level 4 and light emission at the single-photon level 5 .1Since the first demonstration of GaAs NW LEDs in 1992 6 , different geometries and materials have been used to produce NW LEDs operating over a wide range of wavelengths 3, 7-10 . Single-NW LEDs with doping modulation in the axial direction, which is the most interesting geometry for many applications, have been fabricated using GaN-GaInN multi-junctions 3 and a proof-of-principle device has been shown using InP 7 . In this letter we describe the fabrication and characterization of reproducible axial InP NW LED devices, and show that an active InAsP quantum dot region can be incorporated into these devices. The axial geometry allows for controllable injection of electrons and holes into the precisely defined active region, with the additional advantage of high light-extraction efficiency since the optically active region is not embedded in a high refractive index material. Unlike GaInN, InAsP emission can be tuned to infra-red telecommunications wavelengths where there is strong interest in electrically driven single-photon sources 11 .Nanowire p-n junctions were reproducibly grown in the vapor-liquid-solid (VLS) growth mode 12 by use of low-pressure metal-organic vapour-phase epitaxy (MOVPE). 20 nm colloidal Au particles were dispersed on (111)B InP substrates, after which the samples were transferred to a MOVPE system (Aixtron 200), and placed on a RF-heated gas foil rotated graphite disc on a graphite susceptor. The samples were heated to a growth temperature of 420 °C under phosphine (PH 3 ) containing ambient at molar fraction χ PH3 = 8.3×10 -3 , using hydrogen as carrier gas (6 l/min H 2 at 50 mbar). After a 30 s temperature stabilization step, the NW growth was initiated by introducing trimethyl-indium (TMI) into the reactor cell at a molar fraction of χ TMI = 2.2×10 -5 . During the first 20 minutes, hydrogen sulfide (χ H2S = 1.7×10 -6 ) was used for n-type doping, after which the p-type NW part was g...

Quantum dots in the GaAs/AlxGa1−xAs core-shell nanowires: Statistical occurrence as a function of the shell thickness

“…[1][2][3][4][5][6][7][8][9] The integration of QDs in one-dimensional crystals (nanowires, NWs) has increasingly gained interest because of the improvement in the photon extraction efficiency and overall functionality. [10][11][12][13][14][15][16][17][18][19] Recently, it has been shown that self-segregation processes in ternary Al x Ga 1Àx As shells lead to the observation of luminescence stemming from 3D confined excitons. Several high-resolution imaging methods have demonstrated that the Al x Ga 1Àx As shells are indeed not homogeneous and contain nanoscale Ga-rich islands.…”

Single Electron Charging in Optically Active Nanowire Quantum Dots

“…Prior to the work presented here, we have shown that a single InAsP quantum dot grown in an InP nanowire geometry is optically active, exhibits narrow emission lines, spin polarization memory effects, 10 and can be embedded in a LED device geometry. 11 Furthermore, it is predicted that NW-QDs are ideal sources of entangled photons due to the nanowire symmetry. 12 Recently, an electron spin-to-charge conversion read-out scheme has been proposed, 13 which is compatible with controlled storage of carriers up to microseconds.…”

“…Nanowire Growth and Device Fabrication. The nanowire quantum dots were grown in the vaporliquid-solid mode 28 by means of metal-organic vaporphase epitaxy in a similar manner as reported by Minot et al 11 Colloidal Au particles of 20 nm diameter were used to first grow an InP section for 20 min (∼2 µm) followed by 1 s of InAsP growth. The ∼4 µm long nanowires were completed by another 20 min of InP growth.…”

Ferromagnetic GaAs/GaMnAs Core−Shell Nanowires Grown by Molecular Beam Epitaxy

“…[12][13][14] Semiconductor nanowires have been intensively studied due to their great potential for nanoscale electronics and photonics. 4,15 The growth of III-V nanowires using a metal (usually gold) as a catalyst is commonly explained within the vapor-liquid-solid (VLS) mechanism. 16 For a long time chemical vapor deposition (CVD) or chemical beam epitaxy (CBE) were the common techniques used.…”