Hall Effect Investigation on Lithium-Diffused Gallium Arsenide

Hall effect results on GaAs crystals into which Li is introduced at 500°C, as well as at higher temperatures, and subsequently removed in Ga or in air at 500°C are reported. Four acceptor ionization energies: 0.023 and 0.11 eV (previously reported), 0.05 eV and 0.14 eV are found. The two levels 0.023 and 0.05 eV are attributed to Li self-pairs. The 0.11- and 0.14-eV levels are associated with Cu possibly already present in the GaAs crystals. The 0.023-eV level is found in crystals produced by the floating-zone process at all temperatures of the Li diffusion. The 0.023-eV level is also found in the horizontal Bridgman crystals when diffusion is above ∼650°C. Below ∼500°C, however, the 0.05-eV level predominates in Bridgman crystals and the 0.023-eV level is not observed. The origins of the various levels are discussed.