Raytheon/SBRC has demonstrated high quality Si:As IBC IR FPAs for both ground-based and space-based Mid-IR astronomy applications. These arrays offer in-band quantum efficiencies of approximately 50 percent over a wavelength range from 6 micrometers to 26 micrometers and usable responses from 2 micrometers to 28 micrometers . For high background, ground-based applications the readout input circuit is a direct injection (DI) FET, while for low background, space-based applications a source follower per detector (SFD) is used. The SFD offers extremely low noise and power dissipation, and is implemented in a very small unit cell. The DI input circuit offers much larger bucket capacity and better linearity compared with the SFD, and is implemented in a 50 micrometers unit cell. SBRC's Si:As IBC detector process results in very low dark current sand our Raytheon/MED readout process is optimized for very low redout noise at low temperature operation. SBRC is committed to achieving still better performance to serve the future needs of the IR astronomy community.

Semiconductor pixel detectors hold great promise for replacing scintillation cameras in nuclear medicine; improvements in spatial resolution, energy resolution and sensitivity should result. The current status of this subject is briefly reviewed. The fabrication of hybrid, 48 × 48 CdZnTe pixel arrays for use in gamma-ray imaging is described. Each detector array is indium-bump bonded to a Hughes 48 × 48 multiplexer chip; the design is similar to that of an infrared focal-plane array. The 48 × 48 CdZnTe array is shown to perform well as a gamma-ray imaging system with 125 μm spatial resolution (at 60 keV), equivalent to the pixel spacing. A correction technique for charge spreading between pixels is demonstrated. The implications of macroscopic crystal defects on array performance are briefly discussed.

We are developing an imaging technique for nuclear medicine that makes use of semiconductor arrays having a large number of separate pixels on a single slab that are read out by a monolithic integrated circuit called a multiplexer. The device is similar to a focal-plane array used for infrared imaging. Here we present results verifying the concept by using a Hughes 48×48 Ge PIN focal-plane array as a gamma-ray imaging system. The performance of this device as an imaging spectrometer was extraordinary, with a spatial resolution of 125 μm at 30 keV and an energy resolution of 2 keV FWHM (25-140 keV). The device performed well over a temperature range of 136-200 K. It is concluded that semiconductor detector arrays with multiplexer readout are a very attractive approach for a new generation of nuclear medicine imaging systems

We report on the construction and initial testing of a 48 × 48 CdZnTe array with 125 μm pixel spacing and multiplexer readout. Large portions of the array function well but there was a loss of pixels near one corner of the array due to non-interconnecting indium bumps. This problem is readily correctable. Excellent single-pixel spectra were obtained with a 99mTc source using an adjustment technique that accounts for energy deposited in neighboring pixels. A point-spread function (PSF) taken at 140 keV yielded a spatial resolution of 230 μm, much better than required for nuclear medicine applications. No problems were found that are not readily correctable or of much less significance for CdZnTe arrays having larger pixel spacing. We are now constructing 64 × 64 CdZnTe arrays with 380 μm pixel spacing for use in an ultra-high resolution brain SPECT imaging system.

We report results of gamma-ray imaging and energy-resolution tests of a 48x48 CdZnTe array. Our detectors have 125 mu m square pixel electrodes produced by photolithography and are indium-bump-bonded to a multiplexer readout circuit. Using a collimated beam of 140 keV gamma rays of 120 mu m diameter centered on one pixel, we found that the majority of events produced significant charge deposition in nearby pixels. Charge and energy are transported out of the pixel by charge diffusion, photoelectron range, Compton scattering, and escape of K x rays. These effects also distort single-pixel spectra, although photopeaks are still discernible at 140 keV. When signals from neighboring pixels are summed together to correct for this charge spreading, an energy resolution of 10 keV is obtained at 140 keV. Corrections will be simple; and energy resolution should be better for the 380 mu m pixels of the 64x64 CdZnTe arrays we are constructing for an ultra-high-resolution brain imager.

Hughes has designed a large-area staring Si:As impurity band conduction (IBC) focal plane array specifically for high- background longwave infrared (LWIR) astronomy applications. We derived the design parameters by surveying leading astronomers for their requirements. This paper describes summary results of these requirements and how they were implemented in the design. We discuss preliminary detector and readout data that confirm satisfactory operation. We define current status and plans for fabrication and test of detector/readout hybrids.

A new high resolution and ultra wide field of view imaging high energy x-ray and low energy gamma ray detector is proposed for a future space mission. XMAS is expected to combine are minute angular resolution with 2 or 3 pi field-of-view for continuous monitoring of all sky. It will also have wide energy range from about 10 keV to over 250 keV with excellent energy resolution on the order of a few %. XMAS will be built in the form of a fine coded aperture in a geodesic dome format over a two-dimensional high resolution CdZnTe pixel detector array. It will be designed to have accurate timing information. The major scientific aim of this mission is to observe and monitor continuously gamma-ray bursts, AGNs, transient phenomenon and isolated pulsars with high position, time and energy resolutions.

Hughes has designed a large-area staring Si:As impurity band conduction (IBC) focal plane array specifically for high-background longwave infrared (LWIR) astronomy applications. We derived the design parameters by surveying leading astronomers for their requirements. This paper describes summary results of these requirements and how they were implemented in the design. We discuss preliminary detector and readout data that confirm satisfactory operation. We define current status and plans for fabrication and test of detector/readout hybrids.

The Hughes Technology Center (HTC) has developed a family of high-performance Si:As impurity-band conduction (IBC) hybrid focal plane arrays (FPAs) optimized for low background applications: 58×62 pixels (76-μm pitch), 128×128 pixels (75- and 120-μm pitch), and 256×256 pixels (30-μm pitch). These FPAs exhibit state-of-the-art low noise (<100e-) achieved by using readout arrays fabricated on HTC's CryoCMOS process line. The IBC detector arrays, also fabricated at HTC, exhibit high quantum efficiency over a wide waveband with operating temperature of 4–12 K. In addition, Hughes is developing a 256×256 Si:As IBC FPA for high background applications as well as a 512×512 FPA. Readout development includes design and fabrication of 256×256 readouts with large well size of 1×107e- for the high-background FPA and 512×512 readouts with moderate well size (1×106e-).

We are developing a new kind of gamma-ray imaging device that has sub-millimeter spatial resolution and excellent energy resolution. The device is composed of a slab of semiconductor detector partitioned into an array of detector cells by photolithography and connected to a monolithic circuit chip called a multiplexer (MUX) for readout. Our application is for an ultra-high-resolution SPECT system for functional brain imaging using an injected radiotracer. We report here on results obtained with a Hughes 48 × 48 Ge PIN-photodiode array with MUX readout, originally developed as an infrared focal-plane-array imaging sensor. The device functions as an array of individual gamma-ray detectors with minimal interpixel crosstalk. Linearity of energy response is excellent up to at least 140 keV. The array exhibits excellent energy resolution, ∼ 2 keV at ≤ 140 keV or 1.5% FWHM at 140 keV. The energy resolution is dominated by MUX readout noise and so should improve with MUX optimization for gamma-ray detection. The spatial resolution of the 48 × 48 Ge array is essentially the same as the pixel spacing, 125 μm. The quantum efficiency is limited by the thin Ge detector (0.25 mm), but this approach is readily applicable to thicker Ge detectors and room-temperature semiconductor detectors such as CdTe, HgI2 and CdZnTe.

An extensive material characterization facility has been developed to support a modern epitaxial silicon growth laboratory. The growth laboratory provides material for producing impurity band conduction (IBC) IR detector arrays. The laboratory consists of two sections. Material from the research section is used for producing advanced IBC detectors. Material from the manufacturing section is used for producing detector arrays for producibility studies The characterization facility currently includes a computer-controlled variable temperature Hall effect system, a spreading resistance system, and an electrochemical capacitance-voltage dopant profiling device. A low frequency capacitance-voltage system has been assembled from components for specific use with heavily doped silicon exhibiting impurity band conduction. The variable temperature Hall effect measurement allows determination of majority dopant species and concentration, carrier mobility, and total compensation concentration. Spreading resistance yields rapid doping profile measurement of .1 μm to 100 μm thick epitaxial layers. The electrochemical C-V system allows accurate measurement of sharp doping transitions with the capability of 10 Å resolution. The low frequency C-V system can perform measurements on test samples or completed devices to determine compensation concentration for material doped so heavily that impurity band conduction interferes with the ability of the Hall measurement to provide this information. Representative data from each system will be shown and discussed. Application of each measurement to implement material quality control as well as material development will be examined.