Photoluminescence study of CdTe ZnTe self-assembled quantum dots

We report on optical properties of CdTe self-assembled quantum dots (SADs) grown by molecular beam epitaxy on ZnTe. Formation of SADs was achieved by deposition of 1.5-2.5 monolayers of CdTe at a substrate temperature of 420 degrees C and by applying growth interrupts for few seconds in Cd flux. The resulting dots have a typical diameter of 2 nm and a sheet density of 10(1 2) cm(-2). At T=2 K the photoluminescence (PL) spectra consist of two emiss ion lines. The high-energy line originates from excitonic recombination in a wetting layer while the low-energy emission PL band is assigned to recomb ination in SADs. The increase in temperature up to 70 K does not affect the SADs-related emission intensity. It shifts, however, the PL peak energy to wards low energies and causes a significant narrowing of the PL linewidth, from 80 meV at 1.9 K to 50 meV at 130 K. The activation energy of the therm al quenching of SADs-related PL emission was found to be equal to 47 meV. T his value is three times greater than the one observed in CdTe/ZnTe quantum wells, that is, 12-17 meV. (C) 1999 American Institute of Physics. [S0003- 6951(99)05220-1].