Heterostructures in GaInP grown using a change in V/III ratio

A natural monolayer {111} superlattice (the CuPt ordered structure) is formed spontaneously during organometallic vapor phase epitaxial (OMVPE) growth of Ga_0.52In_0.48P. 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 surface reconstruction and step structure. Thus, heterostructures can be produced by simply changing the flow rate of the P precursor during growth. It is found, by examination of transmission electron microscope (TEM) and atomic force microscope (AFM) images, and the photoluminescence (PL) and PL excitation (PLE) spectra, that order/disorder (O/D) (really less ordered on more ordered) heterostructures formed by decreasing the partial pressure of the P precursor during the OMVPE growth cycle at a temperature of 620 0C are graded over several thousands of Å when PH₃ is the precursor. The ordered structure from the lower layer persists into the upper layer. Similarly, D/O structures produced by increasing the PH₃ flow rate yield PL spectra also indicative of a graded composition at the heterostructure. The grading is not reduced by a 1 h interruption in the growth cycle at the interface. Similar heterostructures produced at 670 °C using tertiarybutylphosphine (TBP) as the P precursor show a totally different behavior. Abrupt D/O and O/D heterostructures can be produced by abruptly changing the TBP flow rate during the growth cycle. PL and PLE studies show distinct peaks closely corresponding to those observed for the corresponding single layers. TEM dark field images also indicate that the interfaces 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.