Wuhan Univ, Key Lab Acoust & Photon Mat, Devices Minist Educ, Wuhan 430072, Peoples R China
; Chinese Acad Sci, Inst Semicond, Key Lab Semicond Mat Sci, Beijing 100083, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Lab Nucl Analysis Technol, Beijing 100083, Peoples R China
Self-organized InAs quantum dots (QDs) have been fabricated by molecular beam epitaxy. The authors try to use a slow positron beam to detect defects in and around self-organized QDs, and point defects are observed in GaAs cap layer above QDs. For the self-organized InAs QDs without strain-reducing layer, it is free of defects. However, by introducing a strain-reducing layer, the density of point defects around larger sized InAs QDs increased. The above results suggest that low energy positron beam measurements may be a good approach to detect depth profiles of defects in QD materials. (c) 2007 American Institute of Physics.