Growth Mode and Defect Evaluation of GaSb on GaAs Substrate: A Transmission Electron Microscopy Study

We use transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) techniques to confirm and analyze the interfacial misfit (IMF) and non-IMF growth modes for GaSb epilayers on GaAs substrates. Under optimized IMF growth conditions, only pure 90 dislocations are generated along both [110] and [1-10] directions and located exactly at the epi-substrate interface, which leads to very low density of misfit dislocations propagating from the GaSb/GaAs interface along the growth direction, compared to the non-IMF growth condition. The mechanism of defect annihilation indicates that this IMF mergence process happens without formation of threading dislocations into the GaSb epilayer, which is a completely relaxed growth mode with extremely low defect density. Based on scanning several sets of wafer surfaces, plan-view TEM confirms that the misfit defect densities are estimated to be ∼5 × 10⁵ cm^–2 for IMF growth mode and ∼10⁹ cm^–2 for non-IMF growth mode.