Spatial carrier distribution in InP/GaAs type II quantum dots and quantum posts

Abstract

We performed a detailed investigation of the structural and optical properties of multi-layers of InP/GaAs quantum dots, which present a type II interface arrangement. Transmission electronic microscopy analysis has revealed relatively large dots that coalesce forming so-called quantum posts when the GaAs layer between the InP layers is thin. We observed that the structural properties and morphology affect the resulting radiative lifetime of the carriers in our systems. The carrier lifetimes are relatively long, as expected for type II systems, as compared to those observed for single layer InP/GaAs quantum dots. The interface intermixing effect has been pointed out as a limiting factor for obtaining an effective spatial separation of electrons and holes in the case of single layer InP/GaAs quantum-dot samples. In the present case this effect seems to be less critical due to the particular carrier wavefunction distribution along the structures.

Optical properties of multi-layer type II InP/GaAs quantum dots studied by surface photovoltage spectroscopy

“…In accordance with the discussion of these PL peaks, presented in Ref. 4, the low-energy SPV band is ascribed to optical transitions in the InP QDs, coupled in QPs, due to the narrow spacers, while the high-energy one is attributed to optical transitions, related to the WL. This conclusion is supported by the simultaneous analysis of the SPV amplitude and phase spectra, performed by means of our vector model 17 for the representation of the SPV signal.…”

“…Transmission electron microscopy (TEM) images reveal that the QDs in the first layer are smaller than the measured thickness of the GaAs spacer layer, which is $3 nm. 4 Therefore these QDs are physically separated from the next InP layer. This separation decreases for the subsequent layers and the dots after the fourth layer coalesce into a quantum post (QP)like 19 structure.…”

“…More details about the structural characterization of the samples are given elsewhere. 4 Typical SPV amplitude and phase spectra of the QD sample, measured at 73 K, are presented in Fig. 2.…”

“…The electron-hole wave function spatial overlap is also much smaller for type II QDs, resulting in relatively long carrier lifetimes. 3,4 Due to these properties and their near-infrared ($0.95 pm) optical transition energies, InP/ GaAs QDs are promising candidates for optical memories and optical communication devices.…”

Estudo De Pontos Quânticos De in as P Ingap Para Compor Uma Célula Solar De Banda Intermediária

“…Capítulo 3. Simulações e resultados Na simulação dos pontos quânticos de InP, a wetting layer era fixa em 2 nm (21). Já para pontos quânticos de InAsP, a WL varia com a quantidade de de As no PQ.…”