INASSBBI ALLOYS GROWN BY ORGANOMETALLIC VAPOR-PHASE EPITAXY

A major remaining challenge for III/V semiconductor materials is the development of materials for photonic devices operating in the infrared region of the spectrum. Atmospheric transmission windows exist in the wavelength ranges from 2 to 4.5 and from 8.5 to 12 mum. Thus, emitters and, particularly, detectors operating in these wavelength ranges are important for many applications. Materials for devices operating in the longer-wavelength 8-12 mum region have typically not been III/V semiconductors because the lowest-band-gap conventional III/V alloy is InAsSb, with a 77 K band gap of 0.145 eV, corresponding to a wavelength of 8.5 mum. Previous work has shown that the addition of Bi to InAsSb alloys grown by organometallic vapor-phase epitaxy results in a rapid reduction in the band-gap energy. However, very low temperatures were required to obtained significant levels of Bi incorporation into the solid, due to the immiscibility of Bi in InAsSb. The low growth temperatures result in high carbon contamination levels using conventional precursors. Clearly, new precursors are required for low-temperature growth of these alloys without excessive levels of carbon contamination. New results for the organometallic vapor-phase-epitaxy growth of InAs1-x-ySbxBiy alloys are presented using the novel precursors tertiarybutylarsine, tertiarybutyldimethyl-antimony, and ethyldimethylindium. Alloys have been studied over the entire range of Sb/As ratios in the solid. For growth at 350-degrees-C, the maximum Bi concentration yielding layers without the presence of a liquid second phase was found to be highest for x = 0 (y = 0.045) and lowest for x = 0.7 (y = 0.015). These levels of Bi incorporation yield calculated 77 K band gaps of 0.08 eV for the alloy with x = 0. 5 and y = 0.015. These layers have several orders of magnitude lower levels of carbon contamination than reported previously.