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Title: Phosphorus Diffusion Mechanisms and Deep Incorporation in Polycrystalline and Single-Crystalline CdTe

A key challenge in cadmium telluride (CdTe) semiconductors is obtaining stable and high hole density. Group I elements substituting Cd can form ideal acceptors but easily self-compensate and diffuse quickly. For example, CdTe photovoltaics have relied on copper as a dopant, but copper creates stability problems and hole density that has not exceeded 1015 cm-3. If hole density can be increased beyond 10^16 cm-3, CdTe solar technology can exceed multicrystalline silicon and provide levelized costs of electricity below conventional energy sources. Group V elements substituting Te offer a solution, but are very difficult to incorporate. Using time-of-flight secondary-ion mass spectrometry, we examine bulk and grain boundary (GB) diffusion of phosphorous (P) in CdTe in Cd-rich conditions. We find that in addition to slow bulk diffusion and fast GB diffusion, there is a fast bulk diffusion component that enables deep P incorporation in CdTe. Detailed first-principles calculations indicate the slow bulk diffusion component is caused by substitutional P diffusion through the Te sublattice, whereas the fast bulk diffusion component is caused by P diffusing through interstitial lattice sites following the combination of a kick-out step and two rotation steps. The latter is limited in magnitude by high formation energy, but ismore » sufficient to manipulate P incorporation. In addition to an increased physical understanding, this result opens up new experimental possibilities for Group V doping in CdTe materials.« less
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Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 2331-7019
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Applied; Journal Volume: 5; Journal Issue: 5
American Physical Society
Research Org:
NREL (National Renewable Energy Laboratory (NREL), Golden, CO (United States))
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
14 SOLAR ENERGY; 36 MATERIALS SCIENCE CdTe; diffusion; group V; grain boundary; polycrystalline; single crystal