Dopant-dependent formation and annealing of the dominant native deep-level defect in liquid-phase epitaxial AlGaAs

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Abstract
In liquid-phase epitaxial GaAs the hole traps with levels at EV+0.40 eV and EV+0.70 eV (labeled A and B) are commonly observed. Here, AlGaAs LPE layers doped with Mg, Zn, Si, Ge, Sn, or Te are investigated in order to assess the solubility and the annealing characteristic of both hole traps. It is shown that the concentration of the traps is strongly dependent on the incorporated impurity. The formation of the underlying native defect is determined by the type of conductivity, the amount of the dopant, as well as the lattice site occupied by the impurity atom. The mechanism of dopant-induced solubility is clearly demonstrated for a particular deep-level defect in a semiconductor. Experimental evidence is given that the formation of the native defect in n-type material is enhanced by Ga-site dopants. The solubility characteristic unambiguously reveals that the native defect is mobile at temperatures above 550 °C and that the deep levels are of acceptorlike character. By incorporating high concentrations of As-site dopants the formation of the native defect is significantly suppressed in n-type as well as in p-type material. Therefore, it is suggested that the native defect studied here is linked with the As lattice site. The GaAs antisite defect model is corroborated with regard to the charge character, the defect site, and the two coupled charge states. Usually, the native defect is stable against thermal treatment. Annealing, most likely due to a defect reaction, is observed only in the presence of Ge or Si.