Physics Seminar – Shengqiang Zhou on Pushing the Tellurium doping limit in Si by ion implantation for infrared optoelectronics

Tuesday, July 09, 2024 | By

Please join us on Thursday July 25th, from 11:00am-12:00pm in GSB 306 for Shengqiang Zhou’s seminar on Pushing the Tellurium doping limit in Si by ion implantation for infrared optoelectronics.

Physics Department Seminar

Shengqiang Zhou
Helmholtz-Zentrum Dresden-Rossendorf

Thursday July 25th, 2024
11:00am – 12:00pm, Room: GSB 306

Pushing the Tellurium doping limit in Si by ion implantation for infrared optoelectronics
Tellurium is one of the deep-level impurities in Si, leading to states of 200-400 meV below the conduction band.   Non-equilibrium methods allow for doping deep-level impurities in Si well above the solubility limit, referred as hyperdoping, that can result in exotic properties, such as extrinsic photo-absorption well  below the Si bandgap [1]. The hyperdoping is realized by ion implantation and pulsed laser melting. We will present the resulting optical and electrical     properties as well as perspective applications for infrared photodetectors. With increasing the Te concentration, the samples undergo an insulator to metal transition [2]. The electron concentration obtained in Te-hyperdoped Si is approaching 1021 cm-3 and does not show saturation [3]. It is even higher than that of P or As doped Si, and mid-infrared localized surface plasmon resonances (LSPR) are also observed [4]. Using Te-doped Si, we demonstrate the room-temperature operation of infrared photodetectors with both vertical and planar device geometries (see Figure 1) [5,6]. The key parameters, such as the detectivity, the bandwidth and the rise/fall time, show competitiveness with commercial products. To understand the microscopic picture, we have performed Rutherford backscattering/channeling angular scans and hard x-ray spectroscopies [4, 7]. The Te-dimer complex sitting on adjacent Si lattice sites is the most preferred configuration at high doping concentration. Those substitutional Te-dimers are effective donors, leading to the insulator-to-metal transition, the non-saturating carrier concentration as well as the sub-band photoresponse. Our results are promising for the integration of active and passive photonic elements on a single Si chip, leveraging the advantages of planar CMOS technology.
This work was financially supported by the German Research Foundation (WA4804/1-1, 445049905).