Controlling morphology of NiSb needles in InSb through low temperature gradient horizontal gradient freeze

Abstract

Indium Antimonide (InSb) has been historically grown as poly or single crystals for a variety of electro-optical applications, including infrared windows, Hall sensors, and magnetoresistor devices. When Nickel Antimonide (NiSb) is added to InSb, NiSb needles (hexagonal wurtzite structure) form in the InSb (zincblende F43 m structure) matrix due to a quasi-binary eutectic phase diagram. The size and morphology of the NiSb needles in the InSb can be manipulated and used in devices that have a tunable magnetoresistance.In this work, InSb alloyed with 1.8 wt.% NiSb was grown in a Horizontal Gradient Freeze (HGF) furnace with low thermal gradients (1.5–2.5 °C cm−1) and growth rates ranging from 0.05 cm h−1 to 1 cm h−1 in attempts to grow both single crystals and short, high density needles in polycrystalline material. Altering the growth rate resulted in changes to both the InSb grain size as well as the NiSb needle morphology and distribution. The density of NiSb needles in the InSb matrix and the needle length were shown to be predominantly dependent on growth rate, which was subsequently optimized for the final magnetoresistor application. Undoped InSb crystals were also grown at 0.05 cm h−1 via HGF and demonstrated good IR transmission at room temperature.