High internal electric field in a graded-width InGaN/GaN quantum well: Accurate determination by time-resolved photoluminescence spectroscopy

Abstract

Time-resolved photoluminescence (PL), at T=8 K, is used to study a graded-width InGaN/GaN quantum well. Across the sample, the well width continuously varies from ∼5.5 to 2.0 nm corresponding to PL peak energies varying between 2.0 and 2.9 eV and to PL decay rates covering four orders of magnitude. The plot of decay times versus PL energies is very well fitted by a calculation of the electron–hole recombination probability versus well width. The only fitting parameter is the electric field in the well, which we find equal to 2.45±0.25 MV/cm, in excellent agreement with experimental Stokes shifts for this type of samples.

Polarization-induced confinement of continuous hole-states in highly pumped, industrial-grade, green InGaN quantum wells

“…We have measured the temporal decay of several samples at cryogenic and room temperature over a broad range of detection energies comprising the QW ground-state transition and the CHC luminescence. All decays are mono-exponential 23 and the corresponding decay times that result from a deconvolution with the instrument response function 24 are plotted in Fig. 4 (red squares) as a function of detection energy.…”

Femtosecond pump-probe spectroscopy of propagating coherent acoustic phonons inInxGa1−xN∕GaNheterostructures

“…2,3 These phonon oscillations were much stronger than folded acoustic phonon oscillations observed in other semiconductor superlattices. 4,5,6 InGaN/GaN heterostructures are highly strained at high In concentrations giving rise to large built-in piezoelectric fields, 7,8,9,10 and the large strength of the coherent acoustic phonon oscillations was attributed to the large strain and piezoelectric fields. 2 In this paper, we report the generation of strong localized coherent phonon wavepackets in strained layer In x Ga 1−x N/GaN epilayers and heterostructures grown on GaN and Sapphire substrates.…”

High spatial resolution picosecond cathodoluminescence of InGaN quantum wells

“…Because this high defect density should increase the nonradiative recombination of excited carriers, the high luminescence efficiency of InGaN based heterostructures was very surprising. In addition, InGaN exhibits large electric fields 2 ͑some MV/cm͒ in the ͓0001͔ direction in the nanostructures which results in a redshift ͑quantum confined Stark effect͒ of the emission energies 3, 4 and in a separation of the electron and the hole also expected to decrease the radiative recombination probability. A commonly accepted explanation for the high luminescence efficiency of InGaN based nanostructures is provided by random localization of excitons on quantum dots or at compositional fluctuations prohibiting nonradiative recombination.…”