Optical and electrical characteristics of erbium doped solids for quantum technology applications

Theoropoulou, Nafsika

Abstract

This thesis explores the potential of Er:Si for quantum technology applications. The
unique optical transitions of erbium in the 1.5 μm region make it a suitable candidate
for both telecommunication and silicon photonics applications and the properties of the
4I13/2→4I15/2 optical transition in Er:Si have been extensively studied. However, despite
improvements on excitation efficiency and device fabrication there is limited understanding
on the origin and role of defects in the interaction with the silicon matrix and its
effects in the overall material properties. In this work, we investigate the optical and
electrical characteristics of 166-Erbium implanted in intrinsic silicon. The site structure
of the Er:Si ions is analysed and the existence of at least two sites, one of cubic and one
of orthorhombic symmetry is determined. For a series of different concentrations and
annealing recipes variation in photoluminescence (PL) is reported and linked to different
ratios of the two erbium symmetry sites in the samples. Further evidence of unreported
negative thermal quenching of the PL of erbium in any material is presented. In addition
this work reports the first recording of ultra-fast nanosecond relaxation measurements
of erbium in a bulk semiconductor with lifetime τ < 5 ns. Formation of a new electronic
defect state with activation energy Ea ≈ 0.6 eV acting as a middle state between
erbium’s upper excited and ground state is proposed. The optimal temperature for luminescence
emission and maximum lifetime is found to be 850 ◦C. Seebeck measurements
indicate n-type behaviour in the samples with typical coefficient values in the range of
- 1.2 mVK−1. Conductivity is found to reach a maximum for annealing temperatures
of 750 ◦C. No correspondence between optical and electrical measurements was made.
These findings combined with previous optically modulated magnetic resonance and electron
spin resonance studies open new questions on the nature of erbium defect centre
formation and suggest a potential optical spin manipulation which could pave the way for
high temperature quantum platform and sensing applications. Finally, this study is complemented
with proof-of-concept two-pulse photon echo experiments on an Er3+:Y2SiO5
crystal. Low magnetic field wavelength dependent photon-echo was performed following
Zeeman-splitting observation using the photon-echo sequence. Optical coherence of two
energy transitions of site 1 yielded T2 = (2.53±0.3) μs and T2 = (1.14±0.21) μs for two
sites at B = 0.1 T.

Citation

Theoropoulou, N. (2023). Optical and electrical characteristics of erbium doped solids for quantum technology applications. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Oct 6, 2023
• Publicly Available Date: Oct 30, 2023
• Award Date: Sep 29, 2023