Imaging hole-density inhomogeneity in arsenic-doped CdTe thin films by scanning capacitance microscopy

Jiang, Chun Sheng; Moseley, John; Xiao, Chuanxiao; Harvey, Steven P.; Farrell, Stuart; Colegrove, Eric M.; Metzger, Wyatt K.; Al-Jassim, Mowafak M.

doi:10.1016/j.solmat.2020.110468

Title: Imaging hole-density inhomogeneity in arsenic-doped CdTe thin films by scanning capacitance microscopy

Journal Article · Mon Feb 17 00:00:00 EST 2020 · Solar Energy Materials and Solar Cells

DOI:https://doi.org/10.1016/j.solmat.2020.110468· OSTI ID:1602696

Jiang, Chun Sheng ^[1]; Moseley, John ^[1]; Xiao, Chuanxiao ^[1];

^[1]; Farrell, Stuart ^[1];

^[1]; Metzger, Wyatt K. ^[1]; Al-Jassim, Mowafak M. ^[1]

National Renewable Energy Lab. (NREL), Golden, CO (United States)

We report nanometer-scale hole-density imaging in As-doped CdTe films by scanning capacitance microscopy (SCM). The hole-density profiling is validated by contrasting a CdTe cross-section sample made by molecular-beam epitaxy with systematically increased As doping in a staircase pattern over the range of 10¹⁵-10¹⁸/cm³ within a single film. In polycrystalline films, the carrier distribution is significantly nonuniform, with inhomogeneity ranging from several hundred nm to several um and hole density varying by one order of magnitude (low 10^16 to low 10¹⁷/cm³). This nonuniformity is distributed randomly, independent of the grain structure and grain boundaries (GBs). Kelvin probe force microscopy (KPFM) maps the surface potential and is correlated to cathodoluminescence (CL) and SCM by imaging over identical areas. Higher potential and lower CL intensity are found on GBs but not by SCM contrast; this indicates positive GB charging and recombination, but not GB-specific hole-density changes. The overall KPFM potential image is in rough agreement with the SCM carrier distribution and indicates band-edge potential fluctuations. Nonuniform carrier concentration, potential fluctuations, and defect recombination can all cause voltage and performance loss in As-doped CdTe solar technology.

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Research Organization:: National Renewable Energy Lab. (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:: 1602696

Alternate ID(s):: OSTI ID: 1599968

Report Number(s):: NREL/JA-5K00-76039

Journal Information:: Solar Energy Materials and Solar Cells, Vol. 209, Issue C; ISSN 0927-0248

Publisher:: ElsevierCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 7 works

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14 SOLAR ENERGY
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carrier concentration
As-doping
scanning capacitance microscopy
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cathodoluminescence

Title: Imaging hole-density inhomogeneity in arsenic-doped CdTe thin films by scanning capacitance microscopy

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