Electron–hole liquid in GaP the influence of the isoelectronic impurity nitrogen

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Abstract
The radiative recombination of isoelectronic (nitrogen)‐doped GaP is investigated at high optical excitations and low temperatures (T = 2 K). Extensive experimental results on the luminescence in dependence on the excitation intensity, the nitrogen concentration (NN) and its decay behaviour are presented. At low nitrogen concentrations (NN ≦ 1017 cm−3) and highest excitation levels the radiative recombination from an electron–hole liquid (EHL) accompanied by momentum conserving phonons analogous to undoped GaP can be confirmed. At higher nitrogen concentrations in the range of NN = 3 8 × 1017 cm−3 a radiative no‐phonon transition appears from an EHL induced by the isoelectronic impurity nitrogen. The influence of the latter on the energy of the EHL is studied. The rising nitrogen density yields an increase in the EHL work function. At medium and high nitrogen concentrations (NN ≦ 1018 cm−3) a further up to now unknown luminescence band becomes visible arising from the radiative recombination of a “plasma‐like” phase which is strongl influenced by the isoelectronic impurity nitrogen and coexists with the EHL. Its density (np1) depends on the nitrogen concentration. The use of a simplified model basing on the polarization energy of the carriers caused by the short‐range isoelectronic potential enables the understanding of the experimental findings.