First Principle Calculation of the DX-Center Ground-States in GaAs,Al_xGa_<1-x>As Alloys and AlAs/GaAs Superlattices

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The atomistic nature of the deep donor levels referred to as DX centers in GaAs,Al.Ga. ,As alloys and AIAs/ GaAs superlattices is investigated by applying the ab initio self-consistent pseudopotential method to 64-atom super cells. The total energyand force calculations reveal that the most stable state is the I,-distorted atomic con-figuration around a substitutional donor with the neighbouring bond relaxation givenby the effective ionic radius (0.7% for Si..). On the contrary, a negatively chargeddonor with broken-bond configuration is shown to give a metastable state and not theground state even under high hydrostatic pressures. It is found that a deep A. level at-tributable to the DX center is induced by a simple substitutional donor with the ob-tained optimal lattice configuration. The theory successfully explains experimentalresults on the thermal and optical ionization energies for the DX centers.
社団法人日本物理学会の論文
1991-09-15