Correlative study of defects in semiconductors (Research Topic Area: 4.3 Electronic Sensing)
Abstract
Defects in semiconductors can have major adverse effects on device performance. However, the exact role of a specific type of defect in disrupting a device, or exactly how the same defect behaves in different applications (e.g. solar cell vs. laser), or under different device operation conditions, is hardly ever known. Detailed studies of defect structures are commonly reported but usually without making any direct connection to the real impact of the particular defect. Conversely, the detrimental effects of defects are often clearly shown, but the exact nature of the defect is usually unknown. The PIs of this proposal have in the past carried out semiconducting defect research in this fashion, but the approach is clearly not the most efficient nor the most effective way of using both personnel and facility resources: it has also prevented us from extracting the desired information, namely, the direct correlation between defect structure and device function, and possible failure mode. In this project, the PIs propose to combine their collective expertise in material growth, device fabrication, structural, optical, and device characterization, and theoretical modeling. The primary motivation is to develop and demonstrate a new and different approach that will overcome past obstacles and most effectively use available resources. Specifically, we will first identify individual defects on functional devices and investigate their effects, then obtain structural information about the defect(s) and perform theoretical modeling for complete determination of properties. Thus, the general goals of this project are: (1) to achieve a comprehensive understanding of specific types of structural defect (e.g., threading dislocations) in terms of their microscopic structure and impact on electronic and optical properties; (2) to understand how a collection of defects can affect the mesoscale (or macroscale) electrical and optical behavior of optoelectronic materials; and (3) to explore the potential impact of defects on device performance in different applications and under different operating conditions. In order to achieve these goals, several key activities have been identified: (1) target model systems, initially based on GaAs and CdTe, which are well-understood for their intrinsic properties, have broad technology interest, and can be grown with controllable quality (e.g., defect density). Then identify individual defects (focusing on extended defects) that are electrically and/or optically active during device operation, and subsequently determine their atomic structure. (2) understand the possible evolution of the defect structure under device operating conditions. For example, it is well-known that defects often mutate or propagate under intense light illumination or strong carrier injection, and thereby cause device degradation. (3) apply the most advanced modeling tools, based on first-principles density-functional theory (DFT) and related methods, combined with the atomic structure derived by experiment, to calculate the optoelectronic properties, carrier capture rate, radiative and non-radiative recombination rates of the defect. (4) reach an understanding of the functional interplay between different defects and structural imperfections (e.g., point and extended defects) and the resulting mesoscale optoelectronic properties under different device operating conditions.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1610263
Entities
People
- Yong Zhang
Organizations
- Army Contracting Command
- United States Army
- University of North Carolina at Chapel Hill