High p-type doping, mobility, and photocarrier lifetime in arsenic-doped CdTe single crystals

Journal Article · 07 May 2018 · Applied Physics Letters

DOI: https://doi.org/10.1063/1.5029450 · OSTI ID:1437102

Nagaoka, Akira ^[1]; Kuciauskas, Darius  ^[2]; McCoy, Jedidiah  ^[3]; Scarpulla, Michael A.  ^[4]

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1. Kyoto Univ., Kyoto (Japan); Univ. of Utah, Salt Lake City, UT (United States)
2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
3. Washington State Univ., Pullman, WA (United States)
4. Univ. of Utah, Salt Lake City, UT (United States)

Here, Group-V element doping is promising for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe for thin film solar cells, but there are roadblocks concerning point defects including the possibility of self-compensation by AX metastability. Herein, we report on doping, lifetime, and mobility of CdTe single crystals doped with As between 10¹⁶ and 10²⁰ cm^–3 grown from the Cd solvent by the travelling heater method. Evidence consistent with AX instability as a major contributor to compensation in samples doped below 10¹⁷ cm^–3 is presented, while for higher-doped samples, precipitation of a second phase on planar structural defects is also observed and may explain spatial variation in properties such as lifetime. Rapid cooling after crystal growth increases doping efficiency and mobility for times up to 20–30 days at room temperature with the highest efficiencies observed close to 45% and a hole mobility of 70 cm²/Vs at room temperature. A doping limit in the low 10¹⁷/cm³ range is observed for samples quenched at 200–300 °C/h. Bulk minority carrier lifetimes exceeding 20 ns are observed for samples doped near 10¹⁶ cm^–3 relaxed in the dark and for unintentionally doped samples, while a lifetime of nearly 5 ns is observed for 10¹⁸ cm^–3 As doping. These results help us to establish limits on properties expected for group-V doped CdTe polycrystalline thin films for use in photovoltaics.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
• Grant/Contract Number: AC36-08GO28308
• OSTI ID: 1437102
• Report Number(s): NREL/JA--5900-71157
• Journal Information: Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 19 Vol. 112; ISSN 0003-6951
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English