Photovoltaic and Semiconductor Research:
Advancing Controlled Spalling for High-Performance Devices
Our research group is pioneering advancements in semiconductor fabrication with controlled spalling techniques, revolutionizing the way high-efficiency III-V solar cells and semiconductors are manufactured. By leveraging the principles of fracture mechanics, we’ve developed a precise method to exfoliate thin, high-quality semiconductor films from substrates like germanium and gallium arsenide, enabling innovative, cost-effective applications in photovoltaics, microelectronics, and semiconductor devices.
Why Controlled Spalling?
Traditional wafer preparation methods like wafering, chemo-mechanical polishing (CMP), and chemical etching are costly and waste critical materials. Controlled spalling overcomes these limitations by creating a controlled crack to exfoliate films leaving the wafer intact with no need for CMP, reducing production costs and allowing closed-loop reuse and recycling of critical materials.
High‐Efficiency Solar Cells Grown on Spalled Germanium for Substrate Reuse without Polishing
Applications and Impact:
– Reusable Substrates: Spalling enables substrate reuse, significantly lowering costs for III-V solar cells and semiconductors.
– High Device Performance: Devices grown on spalled surfaces achieve 23%+ efficiency, showing spalling’s potential despite morphological defects like arrest lines and river lines.
– Scalable Fabrication: We’re refining wafer-scale spalling for flexible, high-power-density solar cells and microelectronics, with precise control over layer thickness for custom device structures.
The Science:
Though removing devices by fracture might seem like magic, the process involves careful control of residual stress, crystallography that assists or complicates crack propagation, shaping applied stress fields, mixed mode fracture, anisotropic material properties, and surface characterization.
Graduate students in our group will work on advancing techniques in fracture mechanics, mechanics modeling, thin-film deposition, and material characterization. These efforts contribute to improvements in renewable energy and semiconductor technologies, with potential for scalable, cost-effective manufacturing solutions that appropriately steward our critical material resources.
Light-trapping structures fabricated in situ for ultrathin III-V solar cells 
Improving Performance of III-V Solar Cells Grown on Spalled Germanium with Ex Situ Substrate Planarization 
Facet suppression of gallium arsenide spalling using nanoimprint lithography and methods thereof 
Design of Planarizing Growth Conditions on Unpolished and Faceted (100)-Oriented GaAs Substrates Using Hydride Vapor Phase Epitaxy 
Design of Planarizing Growth Conditions on Unpolished and Faceted (100)-Oriented GaAs Substrates Using Hydride Vapor Phase Epitaxy 
Control of Surface Morphology during the Growth of (110)-Oriented GaAs by Hydride Vapor Phase Epitaxy 
Analysis of Crystalline Defects Caused by Growth on Partially Planarized Spalled (100) GaAs Substrates 
Analysis of Crystalline Defects Caused by Growth on Partially Planarized Spalled (100) GaAs Substrates 
In SItu Smoothing 
Planarization of Rough (100) GaAs Substrates via Growth by Hydride Vapor Phase Epitaxy 
Morphology Control of Growth by Hydride Vapor Phase Epitaxy on Faceted GaAs Substrates Produced by Controlled Spalling for Low Cost II-V Devices 
24% Single‐Junction GaAs Solar Cell Grown Directly on Growth‐Planarized Facets Using Hydride Vapor Phase Epitaxy