High dopant activation in arsenic doped single-crystal CdTe thin films: Insights from MBE growth and rapid thermal processing

Journal Article · Tue Jul 29 20:00:00 EDT 2025 · APL Materials

DOI: https://doi.org/10.1063/5.0260313 · OSTI ID:2584014

Lott, Hongling  ^[1]; Mathew, Andrea T.  ^[2]; Young, Matthew R.  ^[1]; Goldstone, Alexander  ^[3]; Rice, Anthony D.  ^[1]; Reese, Matthew O.  ^[1]; Colegrove, Eric  ^[1]

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1. National Renewable Energy Laboratory (NREL), Golden, CO (United States)
2. National Renewable Energy Laboratory (NREL), Golden, CO (United States); Colorado School of Mines, Golden, CO (United States)
3. Sivananthan Laboratories, Bolingbrook, IL (United States)

Single-crystal model systems are valuable tools to investigate fundamental material properties. In this work, we use molecular beam epitaxy to deposit in situ arsenic (As) doped single-crystal CdTe films on large area Si substrates to better understand As doping for photovoltaic applications. We found that As incorporation is highly temperature dependent: a substrate temperature difference of 50 °C can lead to several orders of magnitude difference in As concentration. Cd overpressure during in situ doping may limit out-diffusion of As but decrease As incorporation, especially at lower growth temperatures. Carrier concentrations greater than 10¹⁶ cm⁻³ can be achieved with or without Cd overpressure when annealed at temperatures above 500 °C. However, unlike the low (∼1% to 5%) dopant activation commonly observed in polycrystalline CdTe, our films achieve significantly higher activation ratios—exceeding 50%, and in some cases approaching 80%. These values are consistent with or exceed prior reports in single-crystal CdTe systems. In addition to as-deposited arsenic concentrations, we also consider arsenic distribution after different rapid thermal processing temperatures. We propose a detailed definition and description of how arsenic incorporation is considered and calculated. Due to carrier concentration saturation, As incorporation also needs to be controlled to average levels of 10¹⁷ cm⁻³ to achieve high activation. These findings suggest that higher annealing temperature regimes may be beneficial to polycrystalline CdTe based PV devices.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
• Grant/Contract Number: AC36-08GO28308
• OSTI ID: 2584014
• Report Number(s): NREL/JA--5K00-92888
• Journal Information: APL Materials, Journal Name: APL Materials Journal Issue: 7 Vol. 13; ISSN 2166-532X
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English