STEP SOURCES IN MICROCHANNEL EPITAXY OF INP

In microchannel epitaxy (MCE) of InP by liquid phase epitaxy (LPE) on InP and InP-coated Si substrates, steps are found as a result of eithe r a misoriented surface or screw dislocations. An atomically flat and step free MCE layer on the InP substrate has been obtained when no scr ew dislocation exists in the microchannel. However, usually as-grown s urfaces of the MCE layer are covered by monolayer steps as a result of spirals, which have been found frequently located at the edges of the MCE layers where locally high interface supersaturation is expected. A single screw dislocation existing in a central area usually cannot g enerate spiral steps, but only perturb the local flow of steps. The ex periment with InP-coated Si substrate which has different widths of th e microchannels has been carried out. The result shows that the thickn ess of the MCE layer is irrelevant to the width of the microchannel. I t is concluded that this happens because the growth is conducted by th e steps from the single-fold spiral generated by only one screw disloc ation usually located near the end of the microchannels. (C) 1998 Publ ished by Elsevier Science B.V. All rights reserved.