Nitrogen-related intermediate band in P-rich GaNxPyAs1\u2212x\u2212y alloys

K. Zelazna,S. Almosni,O. Durand,W. Walukiewicz,A. Létoublon,M. Gladysiewicz,R. Kudrawiec,C. Cornet,M. P. Polak

doi:10.1038/s41598-017-15933-1

Abstract

The electronic band structure of phosphorus-rich GaNxPyAs1−x−y alloys (x ~ 0.025 and y ≥ 0.6) is studied experimentally using optical absorption, photomodulated transmission, contactless electroreflectance, and photoluminescence. It is shown that incorporation of a few percent of N atoms has a drastic effect on the electronic structure of the alloys. The change of the electronic band structure is very well described by the band anticrossing (BAC) model in which localized nitrogen states interact with the extended states of the conduction band of GaAsP host. The BAC interaction results in the formation of a narrow intermediate band (E− band in BAC model) with the minimum at the Γ point of the Brillouin zone resulting in a change of the nature of the fundamental band gap from indirect to direct. The splitting of the conduction band by the BAC interaction is further confirmed by a direct observation of the optical transitions to the E+ band using contactless electroreflectance spectroscopy.

Highlights

Where x is the mole fraction of substitutional N atoms and CNM is a constant, which describes the interaction between the nitrogen level and the conduction band
EM(k) is the energy dispersion of the lowest conduction band of the III-V host, which can be calculated using kp method[11], and EN is the energy of N-related states, all referenced to the top of the valence band of the III-V semiconductor host
The interaction of dispersionless N-related states with the conduction band states leads two highly non-parabolic subbands, E−(k) and E+(k), which are given by Eq (5): E±(k)

Summary

Introduction

Where x is the mole fraction of substitutional N atoms and CNM is a constant, which describes the interaction between the nitrogen level and the conduction band. EM(k) is the energy dispersion of the lowest conduction band of the III-V host, which can be calculated using kp method[11], and EN is the energy of N-related states, all referenced to the top of the valence band of the III-V semiconductor host. The interaction of dispersionless N-related states with the conduction band states leads two highly non-parabolic subbands, E−(k) and E+(k), which are given by Eq (5): E±(k)

Results

Conclusion