Contribution of long lived metastable states to the PL of InP dots in indirect band-gap barrier layers

¹ Groupe d'Étude des Semiconducteurs – CNRS – Université Montpellier II. CC074, 34095 Montpellier Cedex 5, France
² School of Electric and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA

Corresponding author: thierry.taliercio@ges.univ-montp2.fr

Received: 13 July 2006
Revised: 19 September 2006
Accepted: 13 October 2006
Published online: 26 January 2007

Abstract

We report continuous wave and time resolved photoluminescence studies of self-assembled InP quantum dots grown by metalorganic chemical vapor deposition. The quantum dots are embedded into indirect band-gap In_0.5Al_0.5P layers or In_0.5Al_0.3Ga_0.2P layers with a conduction band line-up close to the direct-to-indirect crossover. As revealed by photoluminescence spectra, efficient interdiffusion of species from the barrier layers produces (Al,In)P or (Al,Ga,In)P-dots. This interdiffusion creates potential barriers that are repulsive for electrons of X valleys around the QDs. Both samples show a fast exponential decay component with a time constant between 0.5 and 0.7 ns. In addition, the sample with indirect band gap matrix shows a slow non-exponential time-decay, which is still visible after more than 100 µs. The fast component is attributed to direct recombination of electron-hole pairs in the dots whilst the slow component, which follows a power law t^−0.75 results from recombination of holes in the dots and electrons in metastable states around the dots.