The formation, stability, and suitability of n-type junctions in germanium formed by solid phase epitaxial recrystallization

Design and optimization of n-type doped regions in germanium by solid phase epitaxial recrystallization (SPER) have been studied by the authors. A systematic study is presented of process variables that influence activation and thermal stability, including preamorphization, coimplants, recrystallization temperature, and postrecrystallization thermal treatments. Unlike silicon, activation after recrystallization in germanium is not optimum where the postrecrystallization thermal budget is kept to a minimum. With the aid of modeling, a maximum peak activation of 7× 10¹⁹ cm^-3 was extracted. A steady increase in sheet resistance during postrecrystallization anneals confirms the formation of metastable activation by SPER. It is predicted that active concentrations of 6-8× 10¹⁹ cm^-3 are sufficient to meet targets for sub-20 nm technologies.