Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 15: III-V semiconductors II
HL 15.4: Vortrag
Dienstag, 28. März 2006, 11:45–12:00, POT 51
Evolution of N Defect States and Optical Transitions in Ordered and Disordered GaP1−xNx Alloys — •Eoin OReilly, Clive Harris, and Andrew Lindsay — Tyndall National Institute, Lee Maltings, Cork, Ireland
We show using an sp3s* tight-binding model that the band anti-crossing (BAC) model describes well the evolution of the lowest N-related conduction states in ordered GaP1−xNx alloys, including the evolution of the Γ character with increasing x. We obtain a good description of the lowest conduction states in disordered GaPN structures by explicitly treating the interaction between the GaP host Γ conduction band minimum and defect states associated with a random distribution of N atoms. We find a very similar value for the total Γ character mixed into the N levels in the ordered and disordered cases but a wider distribution of states with Γ character in the disordered case. We show that in the very dilute limit (<0.1%) inhomogeneous broadening of the N state energies prevents the band-gap reduction predicted by the BAC model, while the band-gap reduction at higher composition is determined by the increasing formation of N cluster states. Overall key features of the band structure can be well described using a modified BAC model which explicitly includes the broad distribution of N levels in disordered GaPN alloys.