Effects of Te additions and stirring in the In segregation in Ga1-xInxSb alloys

Abstract

The influence of tellurium in the indium segregation of Ga1-xInxSb:Te ingots obtained by the conventional vertical Bridgman method (CVBM), under stirred and nonstirred conditions, was investigated. Three Te-doped ingots and three no-doped ingots were unidirectionally solidified at a constant speed of 2.0 mm/hour, inside quartz ampoules, closed under argon, and with a conical tip. The furnace temperature was set for overheating between 73.5 – 93°C, and temperature gradients between 3.0 – 3.3°C/mm. The tellurium doped ingots showed a smaller number of grains and no cracks in the middle region of the ingots, right after the tip, in comparison with the no-doped ingots. Moreover, when comparing the stirred with the non-stirred ingots, the EDS experimental profile of indium in Te-doped synthetized without melt stirring ingot showed a better agreement with the Scheil–Gulliver equation than the stirred Tedoped ingots. The Te-doped ingots when stirring the melt during synthesis showed a more constant axial indium distribution, up to 85% of their lengths. The constant lattice estimated from TEM diffraction images are respectively 6.29 Å for the non-doped sample and 6.17 Å for the Te-doped sample. A qualitative account for the increase of the lattice parameter and the Hall measurements results is that the tellurium compensates for the native acceptor defects, contributing to the microstructural quality in the Ga1-xInxSb ingots.