Control of Wigner localization and electron cavity effects in near-field emission spectra of In(Ga)P/GaInP quantum-dot structures

Structural and emission properties of few-electron In(Ga) P/GaInP quantum dots (QDs) representing natural Wigner molecules (WM) and whispering gallery mode (WGM) electron (e) cavities have been investigated. QD structures were grown using self-organized metal-organic vapor phase epitaxy and deposition from similar to 3 to 7 monolayers of InP at 700 degrees C. Using atomic force microscopy, transmission electron microscopy, near-field scanning optical microscopy (NSOM), and mu-photoluminescence (mu-PL) spectra we obtained In(Ga) P/GaInP QDs having lateral size 80-180 nm, height 5-30 nm, Ga content 0.0-0.4, density 2-10 mu m(-2), and electron population up to 20 and demonstrated control of their density and size distribution. Using high-spatial-resolution low-temperature PL spectra, NSOMimaging, and calculations of charge density distributions we observed Wigner localization and e-cavity effects for a series of dots having quantum confinement h omega(0) = 0.5-6 meV. We used these data together with time-resolved PL measurements to clarify the effect of Coulomb interaction and WM formation on emission spectra of few-electron QDs. We present direct observation of 2e, 6e, and 9e WMs; 2e and 4e WGMs; and Fabry-Perot e modes and establish conditions of e-WGM-cavity formation in these QDs.