Emission mechanisms in Al-rich AlGaN/AlN quantum wells assessed by excitation power dependent photoluminescence spectroscopy

Abstract

The optical properties of Al-rich AlGaN/AlN quantum wells are assessed by excitation-power-dependent time-integrated (TI) and time-resolved (TR) photoluminescence (PL) measurements. Two excitation sources, an optical parametric oscillator and the 4th harmonics of a Ti:sapphire laser, realize a wide range of excited carrier densities between 1012 and 1021 cm−3. The emission mechanisms change from an exciton to an electron-hole plasma as the excitation power increases. Accordingly, the PL decay time is drastically reduced, and the integrated PL intensities increase in the following order: linearly, super-linearly, linearly again, and sub-linearly. The observed results are well accounted for by rate equations that consider the saturation effect of non-radiative recombination processes. Using both TIPL and TRPL measurements allows the density of non-radiative recombination centers, the internal quantum efficiency, and the radiative recombination coefficient to be reliably extracted.

AlxGa1−xN‐Based Quantum Wells Fabricated on Macrosteps Effectively Suppressing Nonradiative Recombination

“…Figure b shows that the RT PL lifetime of the MS‐QW on AlN increases with the excitation energy density per pulse. This observation is attributed to the state filling effect of nonradiative recombination centers with photogenerated carriers . The longest lifetime exceeds 2 ns with an energy density of 25 nJ cm −2 , which is comparable to the RT lifetime of InGaN visible QWs.…”

“…PL was detected by a CCD camera through a monochromator. In this study, we selected a weak excitation condition (≈5 nJ cm −2 ) because under such a condition, nonradiative recombination centers are nearly unoccupied, and their influences on the carrier recombination process are clearly observable …”

The effect of plasmonic near field tuning on spontaneous emission intensity of dual emitting ZnO:Er3+ nanoparticles

“…The temporal decay curves exhibit two major decay components that could be fitted into a double exponential equation of the form, Fit = A fast exp (Àt/s fast ) + A slow exp (Àt/s slow ) where fast and slow decay times are represented as s fast and s slow respectively [21]. The inverse of the slow decay time (s slow -À1 ) can be taken as the radiative recombination probability while the inverse of the fast decay component (s fast À1 ) comprise non radiative and radiative recombination probabilities (s fast À1 = s nr À1 + s slow À1 ).…”

“…The inverse of the slow decay time (s slow -À1 ) can be taken as the radiative recombination probability while the inverse of the fast decay component (s fast À1 ) comprise non radiative and radiative recombination probabilities (s fast À1 = s nr À1 + s slow À1 ). The internal quantum efficiency (g) measured from the PL decay curve [21] is calculated [g = (A fast s fast + A slow s slow )/As slow ] to be 15%. The PL emission spectra suggest donor acceptor pair recombination resulting in blue emission.…”

A novel model on time-resolved photoluminescence measurements of polar InGaN/GaN multi-quantum-well structures

“…Also there are some reports attributing this nature to a bi-exponential decay. The work on ultraviolet MQW carried out by Iwata et al 9. suggested that the fast and slow decay components were due to nonradiative and radiative recombination respectively, and the non-exponential nature indicates that IQE is quite low instead of 100% at LT. Ngo et al .…”