Photoluminescence Excitation Spectroscopy of InxGa1xN/GaN Multiple Quantum Wells with Various In Compositions

Sasaki, Chiharu; Iwata, M.; Yamada, Yo; Taguchi, Toshihiko; Watanabe, Satoshi; Minsky, M.S.; Takeuchi, T.; Yamada, Noriyuki

doi:10.1002/1521-3951(200111)228:1<133::aid-pssb133>3.3.co;2-y

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“…When the excitation photon energy drops below 3.5 eV the only significant carrier excitation occurs in the optically thin InGaN QWs which leads to a reduction in the excited carrier density and a subsequent drop in PL intensity. The absorption spectrum of InGaN/GaN QWs is subject to significant inhomogeneous broadening, which is attributed to a combination of the QCSE, the quantum confined Franz-Keldysh effect, [31][32][33] and the effects of alloy disorder, 29,34 and thus as the excitation photon energy is reduced further (below 3.3 eV), the PL intensity falls off progressively rather than exhibiting a sharp cut off at the sub band edge as might be expected. The oscillations observed on the PLE spectra at photon energies below 3.5 eV occur as a consequence of multiple beam interference effects in the sample.…”

Section: Resultsmentioning

confidence: 93%

A comparison of the optical properties of InGaN/GaN multiple quantum well structures grown with and without Si-doped InGaN prelayers

Davies

Hammersley

Massabuau

et al. 2016

Journal of Applied Physics

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In this paper, we report on a detailed spectroscopic study of the optical properties of InGaN/GaN multiple quantum well structures, both with and without a Si-doped InGaN prelayer. In photoluminescence and photoluminescence excitation spectroscopy, a 2nd emission band, occurring at a higher energy, was identified in the spectrum of the multiple quantum well structure containing the InGaN prelayer, originating from the first quantum well in the stack. Band structure calculations revealed that a reduction in the resultant electric field occurred in the quantum well immediately adjacent to the InGaN prelayer, therefore leading to a reduction in the strength of the quantum confined Stark effect in this quantum well. The partial suppression of the quantum confined Stark effect in this quantum well led to a modified (higher) emission energy and increased radiative recombination rate. Therefore, we ascribed the origin of the high energy emission band to recombination from the 1st quantum well in the structure. Study of the temperature dependent recombination dynamics of both samples showed that the decay time measured across the spectrum was strongly influenced by the 1st quantum well in the stack (in the sample containing the prelayer) leading to a shorter average room temperature lifetime in this sample. The room temperature internal quantum efficiency of the prelayer containing sample was found to be higher than the reference sample (36% compared to 25%) which was thus attributed to the faster radiative recombination rate of the 1st quantum well providing a recombination pathway that is more competitive with nonradiative recombination processes.

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