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Improved performance of small pixel infrared detector focal plane arrays via in situ mesa sidewall characterization.


OBJECTIVE: Demonstrate a process capable of in situ sidewall characterization allowing timely feedback for the development of processing and design modifications to improve small pixel infrared FPA performance. DESCRIPTION: Meeting the Army"s need to reduce the size, weight, and power requirements, while increasing the performance of infrared detectors, requires the fabrication of smaller FPA pixels. As the sizes of pixel mesas are reduced, leakage currents from mesa sidewalls become a much greater factor, especially in long and very long wavelength detectors. Small pixel infrared detectors will require passivation of etched sidewall surfaces to achieve higher sensitivity. The lifetime of these detectors or arrays will greatly rely on the long-term stability of the passivated surfaces. It is well known that surface chemistry and morphology play a major role in determining the electrical properties at the semiconductor air interface. However it is progressively more challenging to characterize the sidewall chemical and morphological properties as diode mesa dimensions are reduced to near wavelength dimensions. The ability to characterize these sidewalls in a timely and nondestructive manner will enable the further improvement of processing techniques and the development of robust passivation treatments. This topic solicits innovative ideas for in situ surface characterization techniques that would enable the development of improved sidewall passivation treatments. The proposed technology should have broad range of material applicability to include II-VI and III-V based devices and respective passivation materials. PHASE I: Develop a theoretically valid design for an instrument capable of in situ chemical analysis and morphology measurements of mesa sidewalls with angles>80 degrees and heights ranging from 1 micron to 10 microns in a nondestructive manner. The proposed innovative design must be viable for implementation in phase II. The techniques may include but are not limited to combinations of Raman spectroscopy, Photoluminescence spectroscopy, capacitance-voltage measurements, and surface probe microscopy (SPM). PHASE II: Optimize and implement the design developed in phase I by constructing a prototype instrument. Demonstrate the in situ characterization capabilities of the instrument on III-V and II-VI based long wavelength infrared detector mesas meeting the criteria set forth in phase I. Deliver the prototype instrument for testing. PHASE III: An instrument capable of sidewall characterization (in situ) allowing timely feedback for the development of processing and design will enable the manufacturing of high performance infrared focal plane arrays for improved targeting and detection. By improving the understanding of small pixel sidewalls could enable new commercial applications such as sensor arrays for high-resolution medical imaging, navigation, and fire/rescue aid. Demonstrate equipment at major semiconductor conference exhibitions. REFERENCES: 1. Kim, H. S.; Plis, E.; Gautam, N.; Myers, S.; Sharma, Y.; Dawson, L. R.; Krishna, S., Applied physics letters, 97, 143512, 2010 2. M. Herrera, M. Chi, M. Bonds, N. D. Browning, J. N. Woolman, R. E. Kvaas, S. F. Harris, D. R. Rhiger, C. J. Hill, Applied Physics Letters, 93, 093106, 2008 3. Plis, E.; Rodriguez, J.-B.; Lee, S.J.; Krishna, S. Electronics Letters, 42, 1248, 2006
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