1 Optoelectronics, Department of Photonics Engineering, Technical University of Denmark2 Department of Photonics Engineering, Technical University of Denmark3 École Polytechnique Fédérale de Lausanne4 Universität Dortmund5 Department of Micro- and Nanotechnology, Technical University of Denmark
We present a comprehensive study of the structural and emission properties of self-assembled InAs quantum dots emitting at 1.3 mum. The dots are grown by molecular beam epitaxy on gallium arsenide substrates. Room-temperature emission at 1.3 mum is obtained by embedding the dots in an InGaAs layer. Depending on the growth structure, dot densities of 1-6 x 10(10) cm(-2) are obtained. High dot densities are associated with large inhomogeneous broadenings, while narrow photoluminescence (PL) linewidths are obtained in low-density samples. From time-resolved PL experiments, a long carrier lifetime of approximate to1.8 ns is measured at room temperature, which confirms the excellent structural quality. A fast PL rise (tau (rise) = 10 +/-2 ps) is observed at all temperatures, indicating the potential for high-speed modulation. High-efficiency light-emitting diodes (LEDs) based on these dots are demonstrated, with external quantum efficiency of 1% at room temperature. This corresponds to an estimated 13% radiative efficiency. Electroluminescence spectra under high injection allow us to determine the transition energies of excited states in the dots and bidimensional states in the adjacent InGaAs quantum well.
Ieee Journal of Qantum Eectronics, 2001, Vol 37, Issue 8, p. 1050-1058