GROWTH OF ORDER DISORDER HETEROSTRUCTURES IN GAINP USING A VARIATION IN V/III RATIO/

CuPt ordering, resulting in formation of a natural monolayer {111} sup erlattice, occurs spontaneously during organometallic vapor phase epit axial growth of Ga0.52In0.48P. The degree of order is found to be a fu nction of the input partial pressure of the phosphorus precursor (P-p) during growth. This is thought to be mainly due to the effect of P-p on the surface reconstruction. A change in order parameter is associat ed with a change in the bandgap energy. Thus, a practical application of ordering is the production of a heterostructure by simply changing the now rate of the P precursor during growth. Examination of transmis sion electron microscopy data and photoluminescence spectra indicates that order/ disorder (O/D) (really less ordered on more ordered) and D /O heterostructures formed by growth using PH3 at a temperature of 620 degrees C are graded over several thousands of Angstrom: The ordered structure from the lower layer persists into the upper layer. Similar results were obtained at 620 degrees C when the first layer was grown using PH3 (V/III = 160) and the second using tertiarybutylphosphine (T BP) (V/III = 5). The use af a temperature of 670 degrees C to produce heterostructures using either PH3 or TBP yields a totally different be havior. Abrupt D/O and O/D heterostructures can be produced by changin g P-p during the growth cycle. The cause of this difference in behavio r is not entirely clear. However, it appears to be related to a very s low change in the surface reconstruction, measured using surface photo absorption, when the PH3 partial pressure is changed at 620 degrees C .