Increasing throughput and quality of large area GaSb substrates used in infrared focal plane array production

In this paper we report our success in increasing length of n-type region and decreasing EPD in doped GaSb crystals grown with new oriented seed method. The importance and challenges of growing high quality (low and high doped) GaSb crystals suitable for the routine production of large area focal plane arrays is discussed. Also comparisons and advantages of using oriented seed growth method suitable for wafer production is elucidated. The purity and the stoichiometric ratio of the starting charge has been designed in such a way, the grown crystals have an improved yield of n-type single crystal. This is attributed to the stoichiometric optimization mechanism with respect to the grown-in acceptors, which additionally, has also favoured by decreasing the EPD levels in the grown crystals. Also, we report our recent developments in the bulk growth of large size (up to 25 kg) higher doped crystals grown with oriented seed method, these being required for a new applications of GaSb where very low resistivity substrates are required. The results of quantitative measurements (EDX) as well as structural (dislocation density by EPD assessments and X-Ray analyses) and electrical (carrier concentration by Hall measurements) are presented. High quality crystals (both low and high doped) using the oriented seed method were grown. This work constitutes an important milestone in the development of higher throughput production processes for GaSb substrates which are based upon the volume production of single crystal GaSb boules which meet not only meet well established quality requirements for infrared focal plane array applications but also an emerging set of new GaSb based device technologies which place additional demands on the quality of bulk crystals grown.