Growth Process of GaAs Cap Layers on GaSb/GaAs Quantum Dot Surfaces

Self-assembled GaSb quantum dots (QDs) have been grown on GaAs(001) surface by metal-organic molecular beam epitaxy in the Stranski-Krastanow growth mode. The density of GaSb QDs in a wide range from 5times10⁸ cm^-2 to 4times10¹⁰ cm^-2 can be controlled by changing the growth temperature between 400degC and 510degC. Etching of GaSb QDs was observed by the supply of trisdimethylaminoarcenic and trisdimethylaminoantimony at the temperature above 450degC. Luminescence from the GaSb/GaAs QDs showed a blue shift by the replacement of Sb with As atoms during GaAs cap growth. To realize long-wavelength emission, 2-step growth of GaAs cap layer was proposed. After GaAs QD structure was grown on the terrace surface between neighboring GaSb QDs at 400degC, the GaAs layer was grown to bury the GaSb and GaAs QDs at 450degC. The red shift of the luminescence peak up to 1.22 mum and the improvement of luminescent efficiency of GaSb/GaAs QDs were observed.