Low density 1.55 μm InAs/InGaAsP/InP (100) quantum dots enabled by an ultrathin GaAs interlayer

Abstract

The authors report the formation of low density InAs/InGaAsP/InP (100) quantum dots (QDs) by metalorganic vapor phase epitaxy enabled by an ultrathin GaAs interlayer. For small InAs amount and low group-V flow rate, the QD density is reduced to below 10 QDs/μm2. Increasing the group-V flow rate slightly increases the QD density and shifts the QD emission wavelength into the 1.55 μm telecommunication region. Without GaAs interlayer, the QD density is drastically increased. This is attributed to the suppression of As/P exchange during QD growth by the GaAs interlayer avoiding the formation of excess InAs.

InAs quantum dot growth on planar InP (1 0 0) by metalorganic vapor-phase epitaxy with a thin GaAs interlayer

“…1(d). This reveals suppression of As/P exchange during InAs growth by the GaAs interlayer on InP, as previously shown on InGaAsP [9,10], resulting in better QD quality and smaller size, before the quality of the QDs worsens for too large GaAs interlayer thickness, i.e., tensile strain. In addition to the absence of Ga intermixing in the QDs shown by X-STM [12], intermixing would rather result in an increase of the QD size with GaAs interlayer thickness though also in a PL blueshift.…”

“…This results in too big QDs with too long emission wavelength, rough interfaces, and photoluminescence (PL) line broadening [5,7]. In order to efficiently suppress the As/P exchange reaction, an ultrathin GaAs interlayer was introduced on InGaAsP underneath the InAs QDs [8][9][10].…”

Single InAs1−xPx/InP quantum dots as telecommunications-band photon sources

“…17 However, attempts to grow such dots by molecular beam epitaxy (MBE) did not give the desired results, as growth on (001)-InP substrate generally leads to the formation of quantum dashes or quantum wires, 18,19 while growth on a (311)-InP oriented substrate 20 is not compatible with the standard processes used in the fabrication of photonic devices such as microcavities. Use of metal-organic chemical vapor deposition (MOCVD), on the other hand, has made it possible to grow small InAs 1−x P x /InP islands on a (100)-InP oriented substrate, as it allows for the spontaneous formation of a two-dimensional wetting layer on which small islands can grow, [21][22][23] while their spectral distribution 24 or density 25 can be adjusted during growth. Transmission electron microscopy (TEM) studies on MOCVD-grown samples have shown that the islands are truncated pyramids of diamond-shaped cross section with diagonals of the order of 30 to 40 nm at the top.…”

“…Transmission electron microscopy (TEM) studies on MOCVD-grown samples have shown that the islands are truncated pyramids of diamond-shaped cross section with diagonals of the order of 30 to 40 nm at the top. 24 Although these islands are small enough to have discrete electronic states, sharp spectral lines (identified as exciton and biexciton lines [25][26][27][28] ) are observed only in the short-wavelength side of the luminescence spectrum, from 1.3 μm up to 1.45 μm. By contrast, the emission spectrum around 1.55 μm generally exhibits a large number of low-intensity peaks lying on a broad and intense background, a feature that may be interpreted as corresponding to a continuum of electron-hole states in the InAs 1−x P x island.…”

Design and realization of low density InAs quantum dots on AlGaInAs lattice matched to InP(001)

“…Consequently, to realize a single photon emitting device working in the telecommunications band, quantum dots that emit around 1.55 mm are required with a low surface density (o5 mm À 2 ). The growth of low quantum dot densities (around 10 mm À 2 ) in the InAs/InGaAsP/InP-system was recently demonstrated by MOVPE [12].…”