Free Carrier Reduction in Vacuum‐Annealed S‐, Sn‐, and Ge‐Doped (100) InP

Abstract

Raman scattering has been utilized to examine variations in the free‐carrier concentration of S‐, Sn‐, and Ge‐doped (100) and Si‐doped (100) induced by vacuum annealing the wafers at 500°–550°C for periods ranging from 30 to 60 min. Corrections for the concentration dependence of the conduction electron effective mass have been incorporated analytically. After annealing, reduction of the free‐carrier concentration is observed in all cases; for , the magnitude of the reduction varied from ∼20% for S‐doped material annealed at 550°C for 30 min to 20%–50% for Sn‐ and Ge‐doped samples annealed at 500°C for 1h. A 1h anneal of Si‐doped at 500°C reduced the net free‐carrier density by roughly a factor of 4. Our measurements indicate that if annealing induced dopant “pile up” occurs at the surface because of gettering or the dynamics of surface evaporation, then the dopants either (i) are not electrically active, (ii) have been compensated by defects generated during annealing, or (iii) are piled up within the space‐charge depletion region.