Room temperature exciton-polariton resonant reflection and suppressed absorption in periodic systems of InGaN quantum wells

Abstract

We studied the optical properties of periodic InGaN/GaN multiple quantum well systems with different numbers of periods. A resonant increase in the optical reflection and simultaneous suppression of the optical absorption have been revealed experimentally at room temperature when the Bragg and exciton resonances were tuned to each other. Numerical modeling with a single set of parameters gave a quantitatively accurate fit of the experimental reflection and transmission spectra in a wide wavelength range and various angles of the light incidence. The model included both exciton resonance and non-resonant band-to-band transitions in the InGaN quantum wells, as well as Rayleigh light scattering in the GaN buffer layer. The analysis also involved x-ray diffraction and photoluminescence data. It allowed us to determine the key parameters of the structure. In particular, the radiative broadening of the InGaN QW excitons was evaluated as 0.20 ± 0.02 meV.

Long coherent dynamics of localized excitons in (In,Ga)N/GaN quantum wells

“…Since both signals were measured in transmission, the PL spectrum may be in effect redshifted due to the QW absorption. A Stokes shift as large as 20 meV was observed earlier at room temperature by comparison of the optical absorption and PL spectra for similar samples [17].…”

“…The sample under study was grown with special care to reduce the compositional broadening [6]. Nevertheless, the Stokes shift as large as 20 meV at room temperature [17] indicates a strong lateral localization of the QW excitons. Origin and scale of the potential fluctuations in (In,Ga)N/GaN QWs were investigated by various methods, including transmission electron microscopy [5], near-field scanning optical microscopy [22], and scanning tunneling luminescence spectroscopy [23].…”

“…From the mapping and simulations of high-resolution X-ray diffraction curves described in Ref. [17], the averaged indium concentration and QW width are estimated to be 7.5% and 2.5 nm, respectively, and the measured period of the multiple QW system is about 72 nm, leading to 69.5 nm barrier width. As a result of the periodicity we observed a Bragg reflection peak in the stationary optical reflection spectra [6].…”

FORMATION OF A SUPERRADIANT EXCITON-POLARITON MODE IN A GaN/AlGaN RESONANT BRAGG STRUCTURE

“…Параметры радиационного и нерадиационного затухания в КЯ GaN составили 0.4±0.02 мэВ и 40±5 мэВ, соответственно. Отношение радиационного затухания экситона к нерадиационному в КЯ GaN/AlGaN оказалось в два раза больше, чем в КЯ InGaN/GaN [3,4].…”

Excitonic States and Related Optical Susceptibility in InN/AlN Quantum Well Under the Effects of the Well Size and Impurity Position

“…Added to geometric confinement, the Coulomb interaction between electron and hole ground and excited states leads to large exciton binding energy and a strong optical response for the exciton resonance. This is considered as a key parameter to interpret the experimental photoluminescence (PL) and reflectance spectra [21]- [23]. Recently, this latter is one of the most techniques used with great accuracy to identify exciton states as well as their radiative and nonradiative broadenings compared to the PL spectra.…”