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DOE OSTI · 2583633

Nm-scale electrical resistance imaging on CdTe by scanning spreading resistance microscopy

Jiang, Chun -Sheng [National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000302307500)·Lott, Hongling [National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000157586645)·Mathew, Andrea T. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Colorado School of Mines, Golden, CO (United States)] (ORCID:0009000969028654)·Nardone, M. [Bowling Green State University, OH (United States)] (ORCID:000000034410623X)·Colegrove, Eric [National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000238112193)·Reese, Matthew O. [National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000199275984)
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Abstract

Local resistance imaging can provide information on nm-scale carrier distribution in semiconductor devices. Scanning spreading resistance microscopy (SSRM), an atomic force microscopy-based nm-scale resistance mapping technique, has been developed for carrier delineation in Si microdevices. We report on the development and validation of SSRM on CdTe materials, by testing on molecular beam epitaxy (MBE) grown CdTe films. The probe/CdTe contact resistance was suppressed sufficiently below sample's spreading resistance by pressing the probe into the sample with ∼mN contact force and applying a large sample/probe forward bias voltage (V s ), which was understood by analyzing current-voltage (I-V) involving a serially connected insulating top layer with underlying spreading resistance. The carrier concentration as deduced from the resistance measurement, using a single mobility value, is consistent with Hall measurement with a standard deviation of 14% based on a set of MBE films with carrier concentrations in the range of 10 15 –10 16 /cm 3 . The doping polarity was readily identified by flipping V s polarity, where the resistance with reverse V s is orders of magnitude larger than forward V s . While focusing on the SSRM technique validation, we also show an example on an As-doped Cd(Se,Te) polycrystalline thin film of a high-performance CdTe solar cell, which illustrates the local resistance nonuniformity with up to two orders of magnitude differences, indicating if local mobility is roughly constant, local carrier concentration can have significant nonuniformity.

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14 SOLAR ENERGY72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDSatomic force microscopyelectrical properties and parameterselectrical resistivityepitaxypolycrystalline materialscanning spreading resistance microscopysemiconductorsthin films

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Jiang, Chun -Sheng [National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000302307500), Lott, Hongling [National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000157586645), Mathew, Andrea T. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Colorado School of Mines, Golden, CO (United States)] (ORCID:0009000969028654), Nardone, M. [Bowling Green State University, OH (United States)] (ORCID:000000034410623X), Colegrove, Eric [National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000238112193), Reese, Matthew O. [National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000199275984). 2025-07-30. Nm-scale electrical resistance imaging on CdTe by scanning spreading resistance microscopy. https://doi.org/10.1063/5.0268718

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