Organometallic vapor-phase epitaxy growth and characterization of Bi-containing III/V alloys

Abstract

For potential infrared detector applications, single-crystalline InAsBi and InAsSbBi have been grown by atmospheric pressure organometallic vapor-phase epitaxy. The precursors used were trimethylindium, trimethylantimony, trimethylbismuth, and arsine at growth temperatures of 375 and 400 °C. Good quality epilayers with smooth surface morphologies were obtained by properly controlling the key growth parameter, the V/III ratio. The variation of lattice constant with solid composition for the InAs1−xBix system, a=6.058+0.966x, provides evidence that Bi atoms indeed incorporate substitutionally into the As sites of the sublattice in the InAs zinc-blende structure. An extrapolated lattice parameter for the hypothetical zinc-blende InBi is 7.024 Å. Thermodynamic calculations of the InAs-InBi and InSb-InBi pseudobinary phase diagrams were carried out using the delta-lattice-parameter model using the lattice constant for zinc-blende InBi of 7.024 Å. The results agree well with experimental data. The calculations predict that the solid solubility limit of Bi in InAs is less than 0.025 at. %. The calculated maximum solubility limit is 2.1 at. % for Bi in InSb at the eutectic temperature of 132 °C. Thus, tremendously large miscibility gaps exist in both alloy systems. The critical temperature was predicted to be 2569 °C for the InAs-InBi system and 496 °C for the InSb-InBi system. The miscibility gap is the major factor limiting Bi incorporation into the InAsSb alloys. Nevertheless, metastable InAsBi and InAsSbBi alloys were grown with concentrations far exceeding the solubility limit. For example 3.1 at. % Bi was incorporated into InAs. Infrared photoluminescence measurements show a decrease of peak energy with increasing Bi concentration in the alloys, with dEg/dx=−55 meV/at. %Bi.