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

Abstract

We investigate industrial-grade InGaN/GaN quantum wells (QWs) emitting in the green spectral region under high, resonant pumping conditions. Consequently, an ubiquitous high energy luminescence is observed that we assign to a polarization field Confined Hole Continuum (CHC). Our finding is supported by a unique combination of experimental techniques, including transmission electron microscopy, (time-resolved) photoluminescence under various excitation conditions, and electroluminescence, which confirm an extended out-of-plane localization of the CHC-states. The larger width of this localization volume surpasses the QW thickness, yielding enhanced nonradiative losses due to point defects and interfaces, whereas the energetic proximity to the bulk valence band states promotes carrier leakage. Published by AIP Publishing.

Recombination from polar InGaN/GaN quantum well structures at high excitation carrier densities

“…The TIPL and TRPL spectra shown in Figs. 1 and 4, respectively, are similar to those reported by Sun et al 16 and Nippert et al 21 . In order to investigate further the temporal behavior of the HEB, PL decay transients were measured at various detection energies across the spectrum at a peak excited carrier density of 2.2 × 10 13 cm -2 per pulse and are shown in Fig.…”

“…This observation was explained as being due to the greater electron/hole wave function overlap of the delocalized holes and electrons. Central to the arguments presented by Schulz et al 20 and Nippert et al 21 is that at the high excitation carrier densities localized state saturation occurs resulting in Pauli state blocking similar to that reported in semiconductor quantum dots (QDs) [22][23][24][25][26] . Furthermore, Shahmohammadi et al 27 attributed the high energy emission band observed at high excitation densities to recombination involving an electron-hole plasma whose dynamics were dominated by Auger recombination.…”

“…Following Ref. 21 , we use a Coulomb scattering time of 1 ps. We apply for the lifetimes, τ rec,i , those values for the exponential portions of the decays shown in Fig.…”

“…Importantly, this model neglects the effects of carrier localization as the experiments were performed at room temperature where the authors claim that localization is not important. More recently, Nippert et al 21 reported an in-depth study of a similar high energy emission in green emitting InGaN/GaN multiple QW samples which they attributed to recombination involving a confined hole continuum. Of particular note is that the PL decay curves of the high energy band were single exponentials whose time constants decreased with increasing detection energy.…”

Suppression of the quantum-confined Stark effect in polar nitride heterostructures

“…Therefore, the QCSE in the whole ND series becomes negligible, resulting in the convergence of the total energy shifts against 12 meV (visible in Fig. 3) indicating an ND-band-filling effect [54][55][56] . Hence, the overall emission-peak positions of the confinement regime samples in Fig.…”