Strong normal-incidence infrared absorption in self-organized InAs/InAlAs quantum dots grown on InP(001)

InAs self-assembled quantum dots in InAlAs matrix grown on InP(001) substrates have been fabricated using Stranski-Krastanov growth mode. A strong in-plane polarized intraband absorption in the 10.6-20 mu m wavelength region has been observed and ascribed to a transition from the ground electron state to an excited state confined in the layer plane along the [110] direction. The absorption at normal-incidence reaches 7.8% for ten layers of n-doped quantum dots. The oscillator strength of the intraband transition is comparable to that achieved in quantum wells for a conduction band intersubband transition. The dependence of the intraband absorption on carrier concentration and temperature suggests a quantum-wire type confinement potential. (C) 1999 American Institute of Physics. [S0003-6951(99)04803-2].