Optimized Laser Thermal Annealing on Germanium for High Dopant Activation and Low Leakage Current

Abstract

In this paper, state-of-the-art laser thermal annealing is used to fabricate Ge diodes. We compared the effect of laser thermal annealing (LTA) and rapid thermal annealing (RTA) on dopant activation and electrical properties of phosphorus and Arsenic-doped n+/p junctions. Using LTA, high carrier concentration above 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> was achieved in n-type doped regions, which enables low access resistance in Ge devices. Furthermore, the LTA process was optimized to achieve a diode I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</sub> ratio ~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> and ideality factor (n) ~1.2, as it allows excellent junction depth control when combined with optimized implant conditions. On the other hand, RTA revealed very high I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</sub> ratio ~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> and n ~1, at the cost of high dopant diffusion and lower carrier concentrations which would degrade scalability and access resistance.