Very Heavily Doped N-Type GaAs Obtained With Pulsed Laser Annealing

Abstract

A study of carrier activation and mobility was performed in pulsed laser annealed samples of GaAs implanted with doses of Si and Se from 2.2x1012 to 6.0x1014 cm-2. The samples were annealed using a pulsed XeCl excimer laser ( λ=308 nm) and a pulsed dye laser ( λ=728 nm) with energy densities from 0.1 to 0.9 J/cm2 and a 10 nsec pulse. Very high carrier concentrations of 3x1019 and 1.5x1019 cm-3 were obtained for best n-type GaAs samples annealed with the dye laser and excimer laser, respectively. Dye laser consistently produced higher activation than excimer laser annealing. A transient reflectivity experiment was performed to identify the GaAs melt threshold and the melt phase dynamics of the GaAs,under the nitride cap. The threshold energies for cap damage were 0.34 and 0.12 J/cm2 for excimer and dye lasers, respectively. High carrier activation, as measured by Van der Pauw method, was achieved even for lightly doped samples although the room temperature Hall mobility was low. Raman spectroscopy was used to identify the threshold energies for the GaAs implant layer recrystallization and for optimum carrier activation.