Thermodynamic explanation to the enhanced diffusion of base dopant in AlGaAs-GaAs n p n bipolar transistors
1990; American Institute of Physics; Volume: 56; Issue: 4 Linguagem: Inglês
10.1063/1.102788
ISSN1520-8842
Autores Tópico(s)Semiconductor materials and devices
ResumoA model is presented which accounts for the anomalous diffusion of the p-type base dopant during the growth of AlGaAs-GaAs npn bipolar transistors. The model is based upon Fermi level pinning at the crystal surface during epitaxial growth which leads to an increased concentration of column III interstitial defects in heavily n-type AlGaAs or GaAs. The excess column III interstitials generated in the n-type crystal flow into the p+ base region causing a transfer of the p-type impurity atoms from column III lattice sites to interstitial positions through a ‘‘kick-out’’ mechanism. Once in interstitial positions the impurity atoms are known to diffuse rapidly. The model is consistent with previously proposed mechanisms for both impurity diffusion and column III self-diffusion.
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