Investigation of Hyperdoped Si for Short Wavelength Infrared Focal Plane Array Detectors
Abstract
Investigation of Hyperdoped Si for Short Wavelength Infrared Focal Plane Array Detectors. Infrared detection in Si detectors is limited to the near-IR by the relatively high band gap of Si. One approach to solving this issue is to form an intermediate band (IB) in between the valence and conduction bands, thereby creating a pathway for absorption of photons with energies below the band gap. One way to form an IB in Si is to incorporate impurities at concentrations near the insulator-metal transition (~1019 cm-3). The required concentrations are typically above the solid solubility limits for the impurities in Si, so novel methods to incorporate these dopants at such high levels, which we refer to as hyperdoping, have been the subject of recent research. The method of ion implantation followed by pulsed laser melting (II-PLM) has been shown to achieve the dopant concentrations necessary for IB formation. Recent work on hyperdoping has revealed at least two promising dopant candidates for hyperdoped Si materials: Au and Ti. Si that has been hyperdoped with Au or Ti has been shown to create infrared photoconductivity well below the band gap of pure Si, and prototype photodetectors from these materials have demonstrated the capability of these materials for infrared detection in the SWIR region. The goal of this project is to investigate the feasibility of creating focal plane array (FPA) systems from hyperdoped Si for infrared imaging applications. In order to determine whether hyperdoped Si could be suitable for FPA systems, we will need to determine the optimum dopant and concentration, develop device fabrication protocols, and finally fabricate and test prototype photodetectors from the resulting materials. We will first fabricate a variety of Si samples that have been hyperdoped with Au or Ti at differing concentrations, and then measure structural, optical, and electrical properties. Next, we will use standard complementary metal-oxide-semiconductor (CMOS) processing to fabricate device structures in order to develop recipes for Ohmic contacts to the materials and to make temperature-dependent conductivity measurements. From these results, the optimum dopant and concentration will be chosen for further development, and prototype photodetectors will be fabricated and tested. The dark currents and optical responsivities of the detectors will be measured, and these results will be compared with standard metrics used for evaluation of materials for FPA systems. These results should answer the question of whether Si hyperdoped with Au or Ti is suitable for FPAs. We also present several options for further work toward the goal of hyperdoped Si FPAs.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 23, 2016
- Source ID
- N000141612864
Entities
People
- Jay Mathews
Organizations
- Office of Naval Research
- United States Navy
- University of Dayton