Growth and properties of digitally-alloyed AlGaInP by solid source molecular beam epitaxy

Digital alloying using molecular beam epitaxy (MBE) was investigated to produce AlGaInP quaternary alloys for bandgap engineering useful in 600-nm band optoelectronic device applications. Alternating Ga_0.51In_0.49P/Al_0.51In_0.49P periodic layers ranging from 4.4 monolayers (ML) to 22.4 ML were used to generate 4,000-Å-thick (Al_0.5Ga_0.5)_0.51In_0.49P quaternary materials to understand material properties as a function of constituent superlattice layer thickness. High-resolution x-ray diffraction (XRD) analysis exhibited fine satellite peaks for all the samples confirming that digitally-alloyed (Al_0.5Ga_0.5)_0.51In_0.49P preserved high structural quality consistent with cross-sectional transmission electron microscopy (X-TEM) images. Low-temperature photoluminescence (PL) measurements showing a wide span of luminescence energies ～ 170 meV can be obtained from a set of identical composition digitally-alloyed (Al_0.5Ga_0.5)_0.51In_0.49P with different superlattice periods, indicating the bandgap tunability of this approach and its viability for III-P optoelectronic devices grown by MBE.