Correlative Study of Defects in Semiconductors

Project: Research project

Description

The general goals of this project are: (1) to achieve a comprehensive understanding of specific types of defect (e.g., threading dislocation) in terms of their microscopic structure and impact on electronic and optical properties; (2) to understand how a collection of defects may 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 order to achieve these goals, several specific objectives have been identified:

(1) Select a couple of model systems that 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 under realistic device operation conditions, and subsequently determine their atomic structure.
(2) Understand the possible evolution in the defect structure under realistic device operation conditions. For example, it is well-known that defects often mutate 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, with atomic structures derived from experiment, to calculate the optoelectronic properties, carrier capture rate, radiative and non-radiative recombination rates of the defect.
(4) Understand 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.
Our specific tasks are broken down into two areas as follows:
(1) Material growth with controlled defect densities and device fabrication. The control of defect formation and densities is required for us to study not only the individual defects but also their collective behavior, and predictions of potential for improvement. The primary reason for some device fabrication is not to achieve new performance records or to develop new device structures, but rather to use these devices and their properties to determine which defects most affect device performance and to provide insights into how best to mitigate them in future effort.
(2) Atomic-resolution structural study. What sets our effort apart from many previous efforts is that the defects to be characterized structurally are known to have well-defined electronic and optoelectronic properties, and the atomistic knowledge gained in this thrust will be used as input to the next thrust for theoretical modeling to complete the understanding cycle. Since structural characterization can be challenging, our approach will limit this task to the few types of extended defects that can also be well-characterized by optical means. We will unambiguously answer questions such as: why, for two etch pits, one is manifested as a dark spot in PL but the other is not? We will rely primarily on TEM, complemented by other techniques such as SEM, EDS.
StatusFinished
Effective start/end date5/2/165/1/19

Funding

  • DOD-ARMY-ARL: Army Research Office (ARO): $530,103.00

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defects
atomic structure
thrust
fabrication
carrier injection
radiative recombination
electronics
point defects
illumination
degradation
density functional theory
optical properties
transmission electron microscopy
cycles
scanning electron microscopy
causes
predictions