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Semiconductor Measurement Technology: Improved Characterization and Evaluation Measurements for HgCdTe Detector Materials, Processes, and Devices Used on the GOES and TIROS Satellites David G. Seller, Jeremiah R. Lowney, W. Robert Thurber, Joseph J. Kopanski, and George G. Harman Semiconductor Electronics Division Electronics and Electrical Engineering Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899-0001 April 1994 U.S. DEPARTMENT OF COMMERCE, Ronald H. Brown, Secretary TECHNOLOGY ADMINISTRATION, Mary L. Good, Under Secretary for Technology NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY, Arati Prabhakar, Director National Institute of Standards and Technology Special Publication 400-94 Natl. Inst. Stand. Technol. Spec. Publ. 400-94, 184 pages (April 1994) CODEN: NSPUE2 U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 1994 For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402-9325 TABLE OF CONTENTS Page Abstract 1 Key Words 1 Executive Summary 2 1. Introduction 5 A. Background 5 (1) Infrared Detectors Used on the GOES and TIROS Satellites 5 (2) Previously Published Report on HgCdTe Detector Reliability Study for the GOES Program 8 (3) Fabrication of Photoconductive HgCdTe Infrared Detectors 8 B. Importance of Work Presented Here 10 C. Outline and Organization of Report 11 PART I - HIGH-FIELD MAGNETOTRANSPORT STUDIES 2. Characterization of GOES and TIROS HgCdTe IR Detectors by Quantum Magnetotransport Measurements 13 A. Review of Shubnikov-de Haas (Oscillatory Magnetoresistance) Effect 13 B. Physical Modeling and Fundamental Theory 13 (1) Theory of Shubnikov-de Haas Effect 13 (2) Fourier Transform Analysis 15 (3) Determination of Effective Masses 15 (4) Model for Subbands 17 (5) Determination of Dingle Temperatures 27 (6) Dependence of SdH Signal on Angle of B-field 27 C. Results of Measurements on Specific Detectors 28 (1) Typical Data 28 (2) Results on GOES Detectors 28 (a) Supplier 1 28 (b) Supplier 2 37 (c) Supplier 3 49 (3) Results on TIROS Detectors 62 (4) Intercomparisons 71 D. Summary of Quantum Magnetotransport Characterization Measurements 81 (1) Comparison between Theory and Experiment for Two Different Detector Types 81 (2) Comparison with Detector Performance and Identification of Trends 84 3 . DC Magnetoresistance Characterization of Detectors 85 A. Background 85 B. Theoretical Analysis 85 C. Experimental Work and Results 87 D. Conclusions 96 iii TABLE OF CONTENTS (Continued) Page PART II -OTHER CHARACTERIZATION STUDIES 4. Bonding, Metallization, and Packaging for GOES and TIROS Infrared Detectors . 97 A. Overview and Rationale 97 B. Accomplishments 98 C. Recommended Practice for Wire Bonding and Metallization Used in Radiation Detectors Prepared for Use in GOES, TIROS, and Other Satellites 99 D. Glossary 101 E. Typical Bonding Characteristics and Appearance of Plated Gold Films 102 5. Semiconductor Electronic Test Structures: Appiications to Infrared Detector Materials and Processes 103 A. Introduction 103 B. Conclusions 105 6. Scanning Capacitance Microscopy: A Nondestructive Characterization Tool 106 A. Background 106 B. Applications of SCM to GOES and Related Infrared Detectors 106 C. Establishment of Facility 107 D. Preliminary Results 109 E. Summary 113 7. NIST Review of the GOES Calibration Program 114 A. Purpose 114 B. Summary of Visits to Facilities 114 C. Recommendations 115 8. Summary and Conclusions 117 A. Magnetotransport Measurements 117 B. Other Characterization Studies 118 9. References 120 APPENDICES A. Reprint of Published Paper "Heavily Accumulated Surfaces of Mercury Cadmium Telluride Detectors: Theory and Experiment" B. Reprint of Published Paper "Review of Semiconductor Microelectronic Test Structures with Applications to Infrared Detector Materials and Processes" C. Reprint of Published Paper "Hgi.^Cd^Te Characterization Measurements: Current Practice and Future Needs" IV LIST OF FIGURES Page 1 . 1 Principal components of a HgCdTe GOES detector element 9 2.1a Built-in potential for accumulation layer with total electron density of 8.9 x 10^^ cm'^ and alloy fraction x = 0.191 21 2.1b "E versus k" dispersion relations for the subbands for this potential, showing spin-splitting 22 2.2a Electron density computed by solving Poisson's equation for a charge continuimi and from full quantum-mechanical calculations for the case of figure 2.1b 23 2.2b Calculated subband densities as a function of total density 24 2.3a Subband Fermi energies as a function of total density, measured from the bottom of each subband 25 2.3b Ratio of subband cyclotron effective masses to the free electron mass at the Fermi energy as a function of total density 26 2.4 The ac and dc signals of the magnetoresistance of a typical detector element, 31 IB 29 2.5 The ac signal for detector element 311 IB showing the oscillations imposed on a background which initially rises abruptly and then falls slowly 30 2.6 The ac signal which has been centered by doing a spline fit to the average value of regions of the original signal and then replotting the signal relative to the fit 31 2.7 The ac signal as a function of inverse magnetic field 32 2.8 Fourier transform of the signal in the previous figure 33 2.9 Fourier transforms from elements of two different Supplier 1 detectors, 1 and 2 34 2.10 Subband carrier density versus total density for the Supplier 1 detector elements in figure 2.9 38 2.11 Shubnikov-de Haas traces of four elements of detector 2III1 from Supplier 2 39 2.12 Temperature dependence of the SdH oscillations of element 2III IB 40 2.13 Traces of four elements of detector 2III2 41 2.14 Fourier transforms for the elements of detector 2III1 42 V LIST OF FIGURES (Continued) Page 2.15 Fourier transforms for the elements of detector 2III2 44 2.16 Results of rotating element 2III1B in the magnetic field 45 2.17 Shubnikov-de Haas oscillations from the three Supplier 2 detectors fabricated for diagnostic purposes 46 2.18 Fourier transforms