InSb: A Key Material for IR Detector Applications
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ABSTRACT InSb has served as an important mid-wave IR (,=-3-5pm) detector material for several decades. In this presentation, we will briefly review General Electric's InSb Charge Injection Device technology. Emphasis will be placed on device performance as a function of material parameters. A new InSb materials technology utilizing liquid phase epitaxy will be described. This epitaxial growth technology improves InSb material parameters and increases minority carrier lifetimes by more than two orders of magnitude to near the Auger limit. Comparisons will be made between available bulk material parameters and that of the epitaxial material.
INTRODUCTION Indium Antimonide photodiodes have found numerous applications in the defense industry for more than 20 years. Perhaps the best known (and most successful) of these systems has been the Sidewinder air to air antiaircraft missile. The sensor in this system typically employs one single element InSb photodiode that is cooled by an argon gas Joule-Thompson cooler. More recently, single element diodes have also been employed in commercially available scanned thermal imaging systems. However, progress in penetrating the commercial market has been slow as a result of high detector costs and the necessity of cryogenic cooling for higher performance. To increase the sensitivity and resolution of an infrared imaging system, more high performance detectors are required on the focal plane. This may be achieved by adding additional detectors with a signal wire out of the dewar for each element in the focal plane. At some point, the number of dewar penetrations will become impractical from a thermal loading and packaging standpoint. This has led to the development of advanced focal planes where the signals from many detectors are multiplexed in the dewar to reduce the complexity of the focal plane packaging. At General Electric (GE), the development of focal plane detector arrays consisting of InSb Charge Injection Devices (CID) was initiated in the early 1970's to address these issues'. In addition, silicon integrated circuits have been developed for operation at cryogenic temperatures to perform the signal preamplification and multiplexing functions. One of these advanced focal plane detectors is shown in figure 1.
InSb CHARGE INJECTION DEVICES The InSb CID is a simple Metal Insulator Semiconductor (MIS) capacitor that integrates photogenerated charge in a potential well formed beneath a semi-transparent metal gate. This is shown schematically in figure 2. The potential well is formed by pulsing the gate into deep depletion; at this time charge integration begins. Both photogenerated minority carriers and minority carriers due to dark current are collected beneath the gate during integration. These carriers change the surface potential of the gate
Mat. Res. Soc. Symp. Proc. Vol. 90. ' 1987 Materials Research Society
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electrode. The well is then collapsed by returning the gate voltage to the inversion level causing the integrated charge to recombine (charge injection). T
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