HETEROSTRUCTURES IN GAINP GROWN USING A CHANGE IN V III RATIO/

A natural monolayer {111} superlattice (the CuPt ordered structure) is formed spontaneously during metallic vapor phase epitaxial (OMVPE) gr owth of Ga0.52In0.48P. The extent of this ordering process is found to be a strong function of the input partial pressure of the phosphorus precursor during growth due to the effect of this parameter on the sur face reconstruction and step structure. Thus, heterostructures can be produced by simply changing the flow rate of the P precursor during gr owth. It is found, by examination of transmission electron microscope (TEM) and atomic force microscope (AFM) images, and the photoluminesce nce (PL) and PL excitation (PLE) spectra, that order/disorder (O/D) (r eally less ordered on more ordered) heterostructures formed by decreas ing the partial pressure of the P precursor during the OMVPE growth cy cle at a temperature of 620 degrees C are graded over several thousand s of Angstrom when PH3 is the precursor, The ordered structure from th e lower layer persists into the upper layer, Similarly, D/O structures produced by increasing the PH3 flow rate yield PL spectra also indica tive of a graded composition at the heterostructure. The grading is no t reduced by a 1 h interruption in the growth cycle at the interface. Similar heterostructures produced at 670 degrees C using tertiarybutyl phosphine (TBP) as the P precursor show a totally different behavior. Abrupt D/O and O/D heterostructures can be produced by abruptly changi ng the TBP flow rate during the growth cycle. PL and PLE studies show distinct peaks closely corresponding to those observed for the corresp onding single layers. TEM dark field images also indicate that the int erfaces in both for D/O and O/D heterostructures are abrupt. The cause of the difference in behavior for TBP and PH3 is not clear. It may be related to the difference in temperature. (C) 1997 American Institute of Physics.