Time-resolved gain saturation dynamics in InGaN multi-quantum well structures
Physica Status Solidi C: Conferences 1:10 (2004) 2508-2511
Abstract:
Transient gain spectra were measured for an In0.02Ga 0.98N / In0.16Ga0.84N multiple quantum well using the variable stripe length method (VSLM) in combination with the ultrafast optical Kerr gate (OKG) technique. Gain dynamics were measured for a range of excitation lengths from short (50 μm) to long (350 μm) stripes with the sample under femtosecond photoexcitation. Analysis of the temporal behaviour of gain and chemical potential suggests that stimulated emission originates from a photoexcited electron-hole plasma at early times; at later times localized states dominate as the electron-hole plasma becomes exhausted. Gain reduction at early times is attributable to coupling of the electron-hole plasma with photons along the stripe, whilst localized states are less susceptible to gain saturation. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Carrier relaxation in GaAs v-groove quantum wires and the effects of localization
Physical Review B - Condensed Matter and Materials Physics 70:19 (2004) 1-8
Abstract:
Carrier relaxation processes have been investigated in GaAs/Al xGa1-xAs v-groove quantum wires (QWRs) with a large subband separation (ΔE ≃ 46 meV). Signatures of inhibited carrier relaxation mechanisms are seen in temperature-dependent photoluminescence (PL) and photoluminescence-excitation measurements; we observe strong emission from the first excited state of the QWR below ∼50 K. This is attributed to reduced intersubband relaxation via phonon scattering between localized states. Theoretical calculations and experimental results indicate that the pinch-off regions, which provide additional two-dimensional confinement for the QWR structure, have a blocking effect on relaxation mechanisms for certain structures within the v groove. Time-resolved PL measurements show that efficient carrier relaxation from excited QWR states into the ground state occurs only at temperatures ≳30 K. Values for the low-temperature radiative lifetimes of the ground- and first excited-state excitons have been obtained (340 ps and 160 ps, respectively), and their corresponding localization lengths along the wire estimated.Scanning near-field photoluminescence mapping of (110) InAs-GaAs self-assembled quantum dots
Applied Physics Letters 85:13 (2004) 2535-2537
Abstract:
Scanning near-field optical spectroscopy measurements were carried out for photoluminescence mapping of (110) InAs-GaAs self-assembled quantum dots. Complex line spectra were observed to arise from ground state and excited state ecition complexes. The dot density was found to be about two orders of magnitude lower than in conventional (100) GaAs structures. It was observed that the InAs wetting layer (WL) was relatively rough which may indicate that the thin stress-matching AlAs pre-wetting layer that induced dot growth was not entirely effective.Time-resolved gain saturation dynamics in InGaN multi-quantum well structures
PHYS STATUS SOLIDI C (2004) 2508-2511
Formation of self-assembled InAs quantum dots on (110) GaAs substrates
Applied Physics Letters 83:24 (2003) 5050-5052