Self-assembled nanoholes and lateral QD bi-molecules by molecular beam epitaxy and atomically precise in situ etching

We present a systematic study of nanoholes formation on top of capped InAs quantum dots (QDs) by using AsBr3 in situ etching. The etching. process can be divided into two regimes depending on the nominal etching depth and the thickness of the GaAs cap layer. In the first regime, 6-nm deep and 50-nm wide nanoholes are formed, which we ascribe to a strain selectivity of the etchant. Further supply of the etching gas causes the hole diameter to increase, while the depth stays approximately constant. Photoluminescence (PL) was used to confirm the removal of the buried InAs QDs during etching. The holes can be overgrown with InAs such that an atomically flat surface is recovered. Further InAs deposited on the filled-hole layer forms into pairs of self-assembled QDs-so-called lateral QD bi-molecules. These QD bi-molecules show narrow and intense PL signal at room temperature. (C) 2003 Elsevier Science B.V. All rights reserved.