Measurement and Modeling of Blocking Contacts for Cadmium Telluride Gamma Ray Detectors

Thesis/Dissertation · Thu Jan 07 00:00:00 EST 2010

DOI:https://doi.org/10.2172/990413· OSTI ID:990413

Beck, Patrick R. ^[1]

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1. California Polytechnic State Univ. (CalPoly), San Luis Obispo, CA (United States)

Gamma ray detectors are important in national security applications, medicine, and astronomy. Semiconductor materials with high density and atomic number, such as Cadmium Telluride (CdTe), offer a small device footprint, but their performance is limited by noise at room temperature; however, improved device design can decrease detector noise by reducing leakage current. This thesis characterizes and models two unique Schottky devices: one with an argon ion sputter etch before Schottky contact deposition and one without. Analysis of current versus voltage characteristics shows that thermionic emission alone does not describe these devices. This analysis points to reverse bias generation current or leakage through an inhomogeneous barrier. Modeling the devices in reverse bias with thermionic field emission and a leaky Schottky barrier yields good agreement with measurements. Also numerical modeling with a finite-element physics-based simulator suggests that reverse bias current is a combination of thermionic emission and generation. This thesis proposes further experiments to determine the correct model for reverse bias conduction. Understanding conduction mechanisms in these devices will help develop more reproducible contacts, reduce leakage current, and ultimately improve detector performance.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48; AC52-07NA27344
• OSTI ID: 990413
• Report Number(s): LLNL-TH-425864; TRN: US1007374
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
42 ENGINEERING
22 GENERAL STUDIES OF NUCLEAR REACTORS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ARGON IONS
ASTRONOMY
ATOMIC NUMBER
CADMIUM TELLURIDES
DEPOSITION
DESIGN
FIELD EMISSION
LEAKAGE CURRENT
MEDICINE
NATIONAL SECURITY
PERFORMANCE
SEMICONDUCTOR MATERIALS
SIMULATION
SIMULATORS
THERMIONIC EMISSION
THERMIONICS