Origins of Spectral Diffusion in the Micro-Photoluminescence of Single InGaN Quantum Dots

Abstract

We report on optical characterization of self-assembled InGaN quantum dots (QDs) grown on three GaN pseudo-substrates with differing threading dislocation densities. QD density is estimated via microphotoluminscence on a masked sample patterned with circular apertures, and appears to increase with dislocation density. A non-linear excitation technique is used to observe the sharp spectral lines characteristic of QD emission. Temporal variations of the wavelength of emission from single QDs are observed and attributed to spectral diffusion. The magnitude of these temporal variations is seen to increase with dislocation density, suggesting locally fluctuating electric fields due to charges captured by dislocations are responsible for the spectral diffusion in this system.

Growth of non-polar (11-20) InGaN quantum dots by metal organic vapour phase epitaxy using a two temperature method

“…Non-polar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) InGaN quantum dots (QDs) were grown by metal organic vapour phase epitaxy. An InGaN epilayer was grown and subjected to a temperature ramp in a nitrogen and ammonia environment before the growth of the GaN capping layer.…”

“…It is not clear whether this is a measure of the true linewidth of the emission, or whether the measurement is affected by spectral diffusion. In this letter, an alternative method for the growth of non-polar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) InGaN QDs by metal organic vapour phase epitaxy (MOVPE) is reported, utilising a temperature ramp in an ammonia and nitrogen environment to achieve improved luminescence properties. Low temperature cathodoluminescence (CL) and micro-photoluminescence (µPL) show the presence of sharp peaks in the collected spectra, whose linewidth is limited by the resolution of the detection system.…”

Surface morphology and optical properties of InGaN quantum dots with varying growth interruption time

“…A variety of methods have been developed to grow InGaN QDs. These methods include the surface treatment of the template before QDs growth [6][7][8], the growth parameters adjustment [9][10][11][12][13], the patterned template [14][15][16] and growth interruption method [17][18][19]. By using anti-surfactant or roughing the template surface one will get the InGaN QDs with relatively weak photoluminescence (PL) intensity (the PL intensity of the GaN bandgap peak is even comparable with the intensity of InGaN emission peak).…”

Observations of Rabi oscillations in a non-polar InGaN quantum dot

“…Demonstration of coherent control of quantum dot qubit states in the III-nitride system has been hampered by spectral diffusion caused by intrinsic electric field present in IIInitride quantum dots [10][11] [12]. The non-centrosymmetric nature of the wurtzite crystal structure causes a polarisation discontinuity at the base of the quantum dot and thus an internal electric field which acts to decrease the oscillator strength of the exciton optical transition.…”

“…[28][29] as observed after 2π in figure 3 (c).Another contribution to dephasing comes from the problem of spectral diffusion[10][12] …”