Carrier redistribution between different potential sites in semipolar (202¯1) InGaN quantum wells studied by near-field photoluminescence

Abstract

Scanning near-field photoluminescence (PL) spectroscopy at different excitation powers was applied to study nanoscale properties of carrier localization and recombination in semipolar (202¯1) InGaN quantum wells (QWs) emitting in violet, blue, and green-yellow spectral regions. With increased excitation power, an untypical PL peak energy shift to lower energies was observed. The shift was attributed to carrier density dependent carrier redistribution between nm-scale sites of different potentials. Near-field PL scans showed that in (202¯1) QWs the in-plane carrier diffusion is modest, and the recombination properties are uniform, which is advantageous for photonic applications.

Temporally and spatially resolved photoluminescence investigation of (112¯2) semi-polar InGaN/GaN multiple quantum wells grown on nanorod templates

“…Such a systematic study on ð11 22Þ semipolar InGaN/GaN MQW with high indium content has not yet been reported, even on very expensive free-standing semipolar GaN substrates. [9][10][11][12][13][14]21 The ð11 22Þ semi-polar GaN has been obtained by overgrowth on nanorod templates, which were fabricated using our self-organized nickel nano-mask technique. 6,7 Four samples, each with five periods of InGaN/GaN MQWs were grown on the overgrown ð11 22Þ GaN.…”

High spatial uniformity of photoluminescence spectra in semipolar (202¯1) plane InGaN/GaN quantum wells

“…Interestingly, recent NF measurements at different excitation powers have shown that lateral carrier transport between microscopic different potential sites in ð20 21Þ QWs is limited. 21 This suggests that hot spot formation, caused by the lateral carrier transport into lower potential areas, in ð20 21Þ QW photonic devices is unlikely, which should contribute to their longevity.…”

Polarization-Resolved Near-Field Spectroscopy of Localized States in m -Plane InxGa1−xIvanov1, Marcinkevičius2, Mensi3 et al. 2017Phys. Rev. Applied150100View full textAdd to dashboardCite

“…This indicates that the peak shift is primarily determined by the carrier redistribution between the localized states and not by the band-gap shrinkage. Increased thermal energy allows a carrier transfer across the potential maxima toward deeper states [12]; the full thermalization, however, is not achieved even at 300 K. This is evidenced by the large FWHM showing that carriers are not gathered at the lowest potential minima, as would be expected for the full thermalization case, but are distributed throughout localization minima of different energies [12,22,23].…”

“…Such a behavior would result in a smaller lowtemperature DLP. With increased temperature, hole redistribution toward deeper potential minima takes place [12], reducing the population of the second level and increasing the DLP. At high temperatures, the DLP increase changes to a decrease because of an increasing thermal population of the second VBL.…”

“…Scanning near-field optical microscopy (SNOM) has proven to be a powerful technique to study band potential fluctuations in ternary nitride epitaxial layers, quantum wells (QWs), and light-emitting devices. By providing information on the spatial variation of photo-or electroluminescence spectra with a subwavelength resolution, the technique has enabled studies of material growth mechanisms [1,2], revealed complex relations between band potential fluctuations and recombination [2][3][4][5][6][7][8][9][10], and enabled the exploration of carrier redistribution and band-filling effects [11,12]. Properties of localized states have been studied in QWs of nonpolar and semipolar crystallographic orientations, and correlations between the surface morphology and properties of photoluminescence (PL) parameters have been established [7][8][9][10].…”