Photoluminescence and electronic transitions in cubic silicon nitride.

Luc Museur,Andrei Kanaev,Andreas Zerr

doi:10.1038/srep18523

Abstract

A spectroscopic study of cubic silicon nitride (γ-Si3N4) at cryogenic temperatures of 8 K in the near IR - VUV range of spectra with synchrotron radiation excitation provided the first experimental evidence of direct electronic transitions in this material. The observed photoluminescence (PL) bands were assigned to excitons and excited and centers formed after the electron capture by neutral structural defects. The excitons are weakly quenched on neutral and strongly on charged defects. The fundamental band-gap energy of 5.05 ± 0.05 eV and strong free exciton binding energy ~0.65 eV were determined. The latter value suggests a high efficiency of the electric power transformation in light in defect-free crystals. Combined with a very high hardness and exceptional thermal stability in air, our results indicate that γ-Si3N4 has a potential for fabrication of robust and efficient photonic emitters.

Highlights

A spectroscopic study of cubic silicon nitride (γ-Si3N4) at cryogenic temperatures of 8 K in the near IR VUV range of spectra with synchrotron radiation excitation provided the first experimental evidence of direct electronic transitions in this material
No direct measurements not requiring theoretical correction and/or intuitive extrapolations of the experimental points have been reported until now. In this communication we report on the first investigation of photoluminescence (PL) properties and optical electronic transitions in γ -Si3N4 by time- and energy resolved spectroscopy method
We have examined time- and energy- resolved luminescence of the spinel phase of silicon nitride (γ -Si3N4) at cryogenic temperatures in the near-IR-VUV range of spectra with synchrotron radiation (SR) excitation

Summary

Introduction

A spectroscopic study of cubic silicon nitride (γ-Si3N4) at cryogenic temperatures of 8 K in the near IR VUV range of spectra with synchrotron radiation excitation provided the first experimental evidence of direct electronic transitions in this material. The main part of the industrially used materials for fabrication of LEDs is based today on binary or ternary compounds of the group 13 and 15 elements such as GaN, InN, AlN, GaAs, GaP etc.[1,2] These compounds have a number of disadvantages: All of them are relatively expensive since the group 13 elements are rare in the nature, some of them are considered as toxic (e.g. GaAs), and almost all of them have relatively low efficiencies due to a low exciton binding energy. One of the key values is binding energy of free exciton, which is related to the probability of radiative relaxation of an electron from the conduction to valence band This physical parameter can be calculated from. The hydrogenic-type model adapted for Wannier excitons with a relatively small binding energy is not adequate to γ -Si3N4

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Conclusion