Optical properties of Si-doped GaN

TLDR

The study examined n‑type GaN with Si doping from 5×10¹⁶ to 7×10¹⁸ cm⁻³, modeling photoluminescence broadening as potential fluctuations caused by the random distribution of donor impurities. Photoluminescence linewidth widens from 47 to 78 meV as Si concentration rises, with intensity increasing monotonically, and the experimental data agree with the potential‑fluctuation model, while no Stokes shift at room temperature confirms the intrinsic nature of the near‑band‑edge transition.

Abstract

The optical properties of n-type GaN are investigated for Si doping concentrations ranging from 5×1016 to 7×1018 cm−3. The photoluminescence linewidth of the near-band gap optical transition increases from 47 to 78 meV as the doping concentration is increased. The broadening is modeled in terms of potential fluctuations caused by the random distribution of donor impurities. Good agreement is found between experimental and theoretical results. The intensity of the near-band-gap transition increases monotonically as the doping concentration is increased indicating that nonradiative transitions dominate at a low doping density. The comparison of absorption, luminescence, reflectance, and photoreflectance measurements reveals the absence of a Stokes shift at room temperature demonstrating the intrinsic nature of the near-band edge transition.