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) substra tes 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 sta te to an excited state confined in the layer plane along the [110] directio n. The absorption at normal-incidence reaches 7.8% for ten layers of n-dope d quantum dots. The oscillator strength of the intraband transition is comp arable to that achieved in quantum wells for a conduction band intersubband transition. The dependence of the intraband absorption on carrier concentr ation and temperature suggests a quantum-wire type confinement potential. ( C) 1999 American Institute of Physics. [S0003-6951(99)04803-2].