SURFACE-STRUCTURE CHANGE BETWEEN INGAAS DOTS AND INGAASP FLAT SURFACE-INDUCED BY IN-SITU ARSENIC PHOSPHORUS REPLACEMENT/

In situ arsenic/phosphorus partial pressure control has been examined in order to modify coherent dot structure prepared by self-organized m echanism. The switching of AsH3/PH3 supply onto InGaAs coherent dots a t 480 degrees C causes the replacement of arsenic/phosphorus of the se veral topmost monolayers (MLs), which results in the surface parameter change of the dots. Since strain accumulated between the dots and a s ublayer is changed by the in situ arsenic/phosphorus replacement, the InGaAs dot structure is transformed into a InGaAsP flat surface. The c hange is found reversible, that is, the InGaAs dot structure is brough t back from a flattened surface via the replacement of phosphorus --> arsenic. This in situ arsenic/phosphorus replacement technique is usef ul to make clear the dot formation process, as improved by the ex situ observation of transitional surfaces metastabilized during the dot fo rmation/flattening by a high resolution scanning electron microscope ( HR-SEM). The step by step formation of dots is also demonstrated using the pulse supply of AsH3, which leads advanced dot controls including modulation doping in the dots or composition modulation of the dots. (C) 1998 Elsevier Science B.V. All rights reserved.