Impact of Dopant-Induced Band Tails on Optical Spectra, Charge Carrier Transport, and Dynamics in Single-Crystal CdTe

Patrik Scajev, Algirdas Merkys, Liudvikas Subacius, Sandra Stanionyte, Darius Kuciauskas, Kelvin Lynn, Santosh Swain

Research output: Contribution to journalArticlepeer-review

11 Scopus Citations

Abstract

Cadmium telluride (CdTe) semiconductors are used in thin-film photovoltaics, detectors, and other optoelectronic applications. For all technologies, higher efficiency and sensitivity are achieved with reduced charge carrier recombination. In this study, we use state-of-the-art CdTe single crystals and electro-optical measurements to develop a detailed understanding of recombination rate dependence on excitation and temperature in CdTe. We study recombination and carrier dynamics in high-resistivity (undoped) and arsenic (As)-doped CdTe by employing absorption, the Hall effect, time-resolved photoluminescence, and pump-probe in the 80–600 K temperature range. We report extraordinarily long lifetimes (30 µs) at low temperatures in bulk undoped CdTe. Temperature dependencies of carrier density and mobility reveal ionization of the main acceptors and donors as well as dominant scattering by ionized impurities. We also distinguish different recombination defects. In particular, shallow AsTe and deep VCd−AsCd acceptors were responsible for p-type conductivity. AX donors were responsible for electron capture, while nonradiative recombination centers (VCd−AsTe, As2 precipitates), and native defects (VCd−TeCd) were found to be dominant in p-type and n-type CdTe, respectively. Bimolecular and surface recombination rate temperature dependencies were also revealed, with bimolecular coefficient T−3/2 temperature dependence and 170 meV effective surface barrier, leading to an increase in surface recombination velocity at high temperatures and excitations. The results of this study allowed us to conclude that enhanced crucible rotation growth of As-doped CdTe is advantageous to As activation, leading to longer lifetimes and larger mobilities and open-circuit voltages due to lower absorption and trapping.

Original languageAmerican English
Article number12851
Number of pages10
JournalScientific Reports
Volume12
Issue number1
DOIs
StatePublished - Dec 2022

Bibliographical note

Publisher Copyright:
© 2022, The Author(s).

NREL Publication Number

  • NREL/JA-5900-82747

Keywords

  • cadmium telluride
  • carrier dynamics
  • CdTe
  • electro-optical measurements
  • recombination
  • single crystals

Fingerprint

Dive into the research topics of 'Impact of Dopant-Induced Band Tails on Optical Spectra, Charge Carrier Transport, and Dynamics in Single-Crystal CdTe'. Together they form a unique fingerprint.

Cite this