Ultrathin type-II GaSb/GaAs quantum wells grown by OMVPE

Critical thickness of the 2-dimensional to 3-dimensional transition in GaSb/GaAs(001) quantum dot growth

“…This can unintentionally occur, because the exchange process does not show a well defined signature in RHEED. In this way, the strongly deviating y c values published in the literature can be explained [4][5][6][7][8][9].…”

“…In contrast, for the GaSb/GaAs(001) system widely varying values of y c are reported, ranging over one order of magnitude from 0.4 ML up to 4.0 ML [4][5][6][7][8][9]. This raises the question, whether the GaSb/GaAs system exhibits a different growth mechanism or the determination of reliable y c values is more complicated.…”

Onset of GaSb/GaAs quantum dot formation

“…Since the deposition of only 1 ML GaSb at sample 4 leads to the formation of QDs, as monitored by RHEED, the critical thickness of QD formation, at least at these growth conditions, has to be less than 1 ML, which is in the range of the lowest values reported yet [6,7]. However, this value is only valid for the amount of directly deposited GaSb.…”

“…Antimony is known as surfactant in several material systems [9], exhibiting strong segregation. Thus, during overgrowth of the GaAsSb layers, some Sb atoms may be completely removed from the investigated areas as they remain at the growth front [6,8,9], and some Sb atoms segregate from the deposited layer but get incorporated into the GaAs cap layer [6,8], as can be seen in Fig. 3.…”

“…The critical thickness for QD formation is still under discussion, the reported values vary between about 1 and 4 monolayers (ML) [1,[5][6][7]. Due to the strong segregation of Sb atoms [8,9], a massive change of the shape and chemical composition of QDs and quantum wells (QWs) during overgrowth has to be expected.…”