From visible to white light emission by GaN quantum dots on Si(111) substrate

Abstract

GaN quantum dots (QDs) in an AlN matrix have been grown on Si(111) by molecular-beam epitaxy. The growth of GaN deposited at 800 °C on AlN has been investigated in situ by reflection high-energy electron diffraction. It is found that a growth interruption performed at GaN thicknesses larger than three molecular monolayers (8 Å) instantaneously leads to the formation of three-dimensional islands. This is used to grow GaN/AlN QDs on Si(111). Depending on their sizes, intense room-temperature photoluminescence is observed from blue to orange. Finally, we demonstrate that stacking of QD planes with properly chosen dot sizes gives rise to white light emission.

Internal quantum efficiency of III-nitride quantum dot superlattices grown by plasma-assisted molecular-beam epitaxy

“…9 The possible role of V-shaped pit defects in circumventing carrier dislocations and preventing nonradiative recombination has also been discussed. 10 In order to control and fully exploit the advantages of carrier localization, several groups reported the controlled fabrication of self-assembled InGaN quantum dots [11][12][13][14][15][16] (QDs) and GaN QDs, [17][18][19][20][21][22][23] making use of the lattice-mismatch-induced Stranski-Krastanov growth mode. Due to the presence of strong compressive strain, a film of a few monolayers (ML) of GaN(InGaN) on AlN(GaN) tends to relax elastically via the formation of three-dimensional (3D) islands interconnected by a thin ($1 to 2 ML), highly strained twodimensional (2D) wetting layer.…”

Polarized emission from GaN/AlN quantum dots: Single-dot spectroscopy and symmetry-based theory

“…The wurtzite symmetry generally induces internal electric fields of several MV/cm along the (0001) growth axis. This results in giant quantum-confined Stark effect that, when the QD height is increased over ~2-3 nm, red-shifts exciton energies over hundreds of meV [11,12], yields non-conventional recombination dynamics [13], increasing radiative lifetimes over several orders of magnitude [14] and induces strong electron-hole dipoles that are especially sensitive to their electrostatic environment [15].…”

“…In spite of these challenging experimental conditions, single-dot spectroscopy has been performed on wurtzite GaN/AlN QDs either grown along the (0001) direction [15][16][17][18][19] or along the non-polar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) direction [20,21], which reduces electric field effects. Biexcitonic recombination was identified and studied [16,19,22], as well as spectral diffusion effects [15], Stark shift [23,24], and controlled single photon emission has proven to be at hand [17].…”

Progress in the optical studies of single InGaN/GaN quantum dots

“…Selfassembled QDs were grown using metalorganic chemical vapour deposition (MOCVD) [13,14] and molecular beam epitaxy (MBE) [15][16][17]. Whilst the mechanism of formation of InGaN nanostructures using MBE growth is commonly attributed to a 2D-to-3D transition in the well known Stranski-Krastanow mode, the mechanism associated with the MOCVD growth seems to be more complex and may involve phase separation.…”