Abstract
A key challenge in cadmium-telluride (CdTe) semiconductors is obtaining stable and high hole density. Group-I elements substituting Cd can form acceptors but easily self-compensate and diffuse quickly. For example, CdTe photovoltaics have relied on copper as a dopant, but this creates stability problems and hole density that has not exceeded 1015 cm-3. If hole density can be increased beyond 1016 cm-3, CdTe solar technology can exceed multicrystalline silicon performance and provide levelized costs of electricity below conventional energy sources. Group-V elements substituting Te offer a solution, but they are very difficult to incorporate. Using time-of-flight secondary-ion mass spectrometry, we examine bulk and grain-boundary diffusion of phosphorus (P) in CdTe in Cd-rich conditions. We find that in addition to slow bulk diffusion and fast grain-boundary diffusion, there is a critical fast bulk-diffusion component that enables deep P incorporation in CdTe. Detailed first-principle 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 is sufficient to manipulate P incorporation. In addition to an increased physical understanding, these results open up experimental possibilities for group-V doping in CdTe applications.
Original language | American English |
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Article number | 054014 |
Number of pages | 7 |
Journal | Physical Review Applied |
Volume | 5 |
Issue number | 5 |
DOIs | |
State | Published - 19 May 2016 |
Bibliographical note
Publisher Copyright:© 2016 American Physical Society.
NREL Publication Number
- NREL/JA-5K00-65666
Keywords
- CdTe
- diffusion
- grain boundary
- group V
- polycrystalline
- single crystal