Abstract
A study of the effects of high temperature (1000 °C) thermal annealing for 1 h–16 h on undoped semi-insulating (SI) liquid encapsulated Czochralski GaAs, has been carried out using photo-induced current transient spectroscopy (PICTS), photoluminescence (PL) and Hall effect (HE) techniques. The PICTS data show the presence of a multitude of levels before annealing which are completely annihilated after treatment excepting for the traps EL2 and EL6. The concentration of these traps decrease with increasing annealing time. The authors suggest that this decrease results from the breakup of the arsenic antisite As Ga assumed to be the core of the EL2 and EL6 complexes. The PL results show an increase in the intensity of the 1.36 eV and 1.41 eV emissions, attributed to Cu and Mn impurities, after 16 h annealing. This behaviour is interpreted in terms of an increase of gallium vacancy V Ga concentration after the decomposition of As Ga. HE results show a little decrease in the net carrier concentration when the annealing time is increased up to 4 h. However, the long annealing time (16 h) induces a conversion of the studied sample from semi-insulating to p-type conducting. We suggest that the decrease of carrier concentration is due to the annihilation of the donor level at 0.13 eV. The conversion from SI to p-type is rather related simultaneously to the decrease of EL2 and EL6 and the generation of acceptor levels due to the presence of V Ga .
Published Version
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