Photoluminescence studies of surfactant modified microstructures in gallium indium phosphide

The use of surfactants is a new method of controlling the optical properties of epitaxial layers of III/V semiconductor alloys. During organometallic vapor phase epitaxy (OMVPE) growth of GaInP lattice matched to (001) GaAs substrates, a long range ordering of the Ga and In atoms on the (111) planes typically occurs. Another microstructure observed in GaInP under these conditions is lateral Composition Modulation (CM). Both microstructures reduce the observed band gap, causing an optical polarization, and both occur because of surface properties. Using a surfactant during growth presents a method of controlling the final optical properties of the epitaxial layer. This work investigates that structure-property relationship through photoluminescence of the surfactant modified epilayers of GaInP.; This work is organized into four main sections. First, four surfactant precursors are investigated to remove CuPtB ordering from GaInP, diethyltelluride which is an n-type dopant in GaInP, and three isoelectronic surfactants: triethylarsenic, triethylantimony and trimethylbismuth. Small amounts of these precursors in the vapor are shown to remove CuPtB ordering from GaInP. Arsenic is shown to incorporate strongly while disordering the epilayer. Above Sb/III(v) and Bi/III(v) = 0.016, the observed band gap energy decreases with surfactant concentration. Second, at Sb/III(v) = 0.064, the formation of an ordered phase with a period triple the normal lattice spacing along the [111] and [111] directions is observed. The formation of this new ordered structure is believed to be related to a change in the surface reconstruction. Third, the epilayers are investigated with polarization PL at 12 K which show that PL intensity along the [111] direction is as much as 41 times larger than along [1¯10]. Coincident with this result is the presence of CM along the [110] direction. Fourth, the epilayers modified by Sb are subjected to a detailed investigation using temperature dependent PL, power dependent PL, photoluminescence excitation and time-resolved PL to investigate the underlying source of the unusually high polarization. It is determined that the CM structure is responsible for the unusual polarization. The data is further extended to demonstrate an optical method of measuring the CM amplitude versus Sb concentration.