open access publication

Article, 2024

Overcoming the doping limit in GaAs by ion implantation and pulsed laser melting

Journal of Applied Physics, ISSN 0021-8979, 1089-7550, Volume 135, 4, Page 045703, 10.1063/5.0190600

Contributors

Yu, Kin Man 0000-0003-1350-9642 (Corresponding author) [1] [2] Scarpulla, Michael A 0000-0002-6084-6839 [3] Ho, Chun Yuen 0000-0001-6045-4715 [4] Dubon, Oscar D [2] [5] Walukiewicz, Wladek [2]

Affiliations

  1. [1] City University of Hong Kong
  2. [NORA names: China; Asia, East];
  3. [2] Lawrence Berkeley National Laboratory
  4. [NORA names: United States; America, North; OECD];
  5. [3] University of Utah
  6. [NORA names: United States; America, North; OECD];
  7. [4] University of Southern Denmark
  8. [NORA names: SDU University of Southern Denmark; University; Denmark; Europe, EU; Nordic; OECD];
  9. [5] University of California, Berkeley
  10. [NORA names: United States; America, North; OECD]

Abstract

Most semiconductors exhibit a saturation of free carriers when heavily doped with extrinsic dopants. This carrier saturation or “doping limit” is known to be related to the formation of native compensating defects, which, in turn, depends on the energy positions of their conduction band minimum and valence band maximum. Here, we carried out a systematic study on the n-type doping limit of GaAs via ion implantation and showed that this doping limitation can be alleviated by the transient process of pulsed laser melting (PLM). For n-type doping, both group VI (S) and amphoteric group IV (Si and Ge) dopants were implanted in GaAs. For comparison, p-type doping was also studied using Zn as the acceptor. Implanted dopants were activated by the PLM method, and the results are compared to rapid thermal annealing (RTA). Our results reveal that for all n-type dopants, while implantation followed by the RTA results in a similar saturation electron concentration of 2–3 × 1018 cm−3, the transient PLM process is capable of trapping high concentration of dopants in the substitutional site, giving rise to a carrier concentration of >1019 cm−3, exceeding the doping limit of GaAs. However, due to scatterings from point defects generated during PLM, the mobility of n-type GaAs after PLM is low (∼80–260 cm2/V s). Subsequent RTA after PLM (PLM + RTA) is able to remove these point defects and recover the mobility to ∼1000–2000 cm2/V s. The carrier concentrations of these PLM + RTA samples are reduced but are still a factor of 3 higher than RTA only GaAs. This can be understood as the dopants are already incorporated in the substitutional site after PLM; they are less likely to be “deactivated” by subsequent RTA. This work is significant to the understanding of doping mechanisms in semiconductors and provides a means for device applications, which require materials with ultra-high doping.

Keywords

GaAs, PLM process, Zn, acceptor, annealing, applications, band maximum, band minimum, carrier concentration, carrier saturation, carriers, cm-3, comparison, compensating defects, concentration, conduction band minimum, conductivity, defects, device applications, devices, dopants, doping, doping limit, doping mechanism, electron concentration, energy, energy position, extrinsic dopants, factors, formation, free carriers, group, group IV, group VI, higher concentrations, implantation, implanted dopants, ion implantation, ions, laser melting, limitations, materials, maximum, mechanism, melting, method, minimum, mobility, n-type GaAs, n-type dopant, n-type doping, p-type, p-type doping, position, process, pulsed laser melting, rapid thermal annealing, results, samples, saturation, scattering, semiconductor, sites, study, substitutional sites, systematic study, thermal annealing, transient process, trap high concentrations, valence, valence band maximum

Funders

  • Lawrence Berkeley National Laboratory
  • United States Department of Energy
  • Office of Basic Energy Sciences

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