Glenn T. Hess

Modeling and test of pixel cross-talk in HgCdTe focal plane arrays

Mercury Cadmium Telluride focal plane arrays with well over 1000 pixels have been fabricated for a number of years. These FPAs have been built as large two-dimensional arrays of HgCdTe p-n junction diodes on a single CdTe or CdZnTe substrate. Sensitivity of each pixel to impinging radiation is one of the most important quality factors for these devices. However, material parameters, which give diode high sensitivity, are the same as those that cause cross talk between adjacent diodes in the array. This cross talk causes a blurred image and in general is a detrimental factor for the FPA system. The cross talk modeling is done in a two- dimensional simulation format to achieve high accuracy. In addition, the output information can be generated as a statistical function of the material and design parameter variations. Actual heterojunction FPA devices have been fabricated and tested for cross talk. In the paper, this data is compared to the simulation results. This design method and its algorithms are encapsulated in a software program called IRSIM. This physics-based simulator allows the engineer to use versatile geometries and material concentrations.

HgCdTe double-layer heterojunction detector device

Researchers have studied the use of double layer heterojunction HgCdTe devices for application in focal plane arrays (FPAs). Such devices are built with a wide bandgap semiconductor on top of a narrow bandgap semiconductor. With a highly doped p-type material at the surface, these devices enhance the ability to make contact with the anode side of the diode with interconnect metal. Optimizing FPA performance with heterojunction detectors has posed serious problems because many of the HgCdTes material parameters vary as a function of composition, temperature and doping concentration. AET, with funding from the US Army Night Vision Labs, has developed a new system for design of focal plane arrays using heterojunction HgCdTe detectors. By using this new software modeling technique, a double layer heterojunction detector device has been designed with consideration for many of the material and environmental variations. This paper develops the models employed in the simulation program and will compare the simulation results with experimental data.

Fabrication of thin-reliable multichip modules

The fabrication of thin, reliable multichip modules has been demonstrated by Florida Institute of Technology. This involved developing encapsulation techniques to build multichip modules (MCMs) with a thickness less than 0.05 inches. The ultimate goal of these encapsulation techniques is to provide hermetic performance at a low cost while meeting specific environmental conditions.<<ETX>>

Diamond Sensors with Silicon Technologies for Sensing in Harsh Environments

This paper presents the results of a research program aimed at developing passive and active circuit components to be used in air vehicle applications. The team of Advanced Engineering Technology (AET, Inc.) and Vanderbilt University is developing diamond sensors that will be integrated with a silicon-based integrated circuit for incorporation into air vehicles. Specifically, the team is developing the technology necessary to integrate chemical vapor deposited (CVD) diamond films with the silicon integrated circuit.

Two-color HgCdTe focal plane detector simulation

This paper describes a simulation technology for HgCdTe infrared detectors used in advanced IR focal plane array architectures. This model addresses the material processes needed for fabrication and the electrical characteristics of multi-layer structures covering a wide range of wavelengths from middle wavelength to very long wavelength.

HgCdTe focal plane array cost modeling

Focal plane arrays (FPAs) are used in many applications for detecting infrared (IR) radiation where normal sight with light in the visible spectrum is not possible. To effectively detect this IR radiation, complex semiconductor diodes, cooled to low temperatures, are usually used. The most common of these semiconductor materials is the II-VI alloy semiconductor system using HgCdTe, which is often called MCT. Focal plane arrays with over 1000 pixels have been fabricated. The cost of these very complex systems is becoming a very important consideration in decisions of where to use these FPAs. The focal plane array actually consists of two semiconductor parts with a sophisticated cooling assembly. The semiconductor parts are the MCT detector device itself and a companion device called the read-out circuit. The cost model presented in this paper consists of various expressions as functions of physical parameters that can be measured, calculated from data or estimated. Although accurate absolute cost data may not be available (because it does not exist or is proprietary to a company), cost estimates can be effectively used to determine relative cost between two designs or processes. In addition, when these cost models are coupled with the STADIUM design of experiments simulation methodology, accurate predictions of the most dominant cost drivers can be obtained. This cost model and its algorithms are coupled with a commercial software program called IR-SIM.

Focal plane array design using IR-SIM software system

Heterojunction HgCdTe detector chips are used in military and commercial focal plane array systems. These devices give improved performance because they are built with a wide bandgap semiconductor on top of a narrow bandgap semiconductor. Optimization FPA performance with heterojunction detectors has posed problems because many of the HgCdTe material parameters vary as a function of composition, temperature and doping concentrations. AET, with funding from the US Army Night Vision Labs, has developed a new simulator called IRSIM that automates the HgCdTe device analysis and design. This paper discusses the details of and operation of this simulator.

New IRFPA device model

Existing infrared IRFPA models lack simplicity for setting up the detectors architecture/structure and lack continuity between IR detector material, IR detector processes, detector architecture, and detector operation. Existing models also lack the ability to reveal spatially and quantitatively the full impact of the detectors material, process and architecture on IRFPA performance. This paper discusses the development of a new IRFPA computer model used to simulate existing and future IRFPAs. This model is the first model that evaluates the IR sensor system at the device physics level and provides enhanced quantitative and visual information allowing the device engineer to determine the impact of material quality, processing procedures and IR detector architecture on IRFPA performance in the SWIR-VLWIR region. This new model is combined with powerful statistical techniques that predict IRFPA performance as well as cost. Operation under virtually unlimited user specified conditions allows the engineer to project the performance of a newly designed IRFPA prior to fabrication. The complete model provides outputs at both the device physics and detector level. When interfaced with NVESDs FLIR92 and ACQUIRE, the model provides the ability to analyze effects at the device level of the detector that impact outputs at the system level such as NETD and range.

Heterojunction model for Focal Plane Array detector devices

Night vision systems for military and commercial applications usually use an Infrared Focal Plane Array (IRFPA) for its radiation detector. Existing IRFPA models lack simplicity for setting up the detectors architecture/structure and lack continuity between IR detector material, IR detector processes and detector architecture. This paper will discuss the first version a new IRFPA computer model which is to be used to simulate heterojunction IRFPAs with enhanced quantitative and visual information that allow the device engineer to access the impact of material quality, processing procedures and IR detector architecture on IRFPA performance. This new model will be combined with statistical simulation to enable IRFPA design which have high performance and lowest cost.

3D focal plane array modeling for IRFPA process, operation, and performance simulations

Existing Infrared IRFPA models lack simplicity for setting up the detectors architecture/structure and lack continuity between IR detector material, IR detector processes, detector architecture, and detector operation. The models also lack the ability to reveal spatially and quantitatively the full impact of the detectors material, process and architecture on IRFPA performance. This paper will discuss the development of a new IRFPA computer model which is used to simulate existing and future IRFPAs with enhanced quantitative and visual information that allow the device engineer to access the impact of material quality, processing procedures and IR detector architecture on IRFPA performance in the SWIR-VLWIR region. This new model will be combined with statistical simulation to provide high IRFPA performance and lowest cost.