Graduation Year

2004

Document Type

Thesis

Degree

M.S.E.E.

Degree Granting Department

Electrical Engineering

Major Professor

Morel, Don L.

Keywords

parameter extraction, bulk recombination, surface recombination, photoconductors, HgI₂

Abstract

Mercuric Iodide is the most promising of all semiconductor materials currently under investigation for use as radiation detectors at room temperature. While substantial studies have been conducted on single crystal HgI₂, polycrystalline HgI₂ remains a comparatively less studied form. The HgI₂ films are deposited on TEC-15 LOF glass with a Tin Oxide (SnO₂) coating which acts as the growth surface and front contact. The back contact, Palladium (Pd), is deposited by sputtering through a shadow mask. The films are circular in shape with an approximate diameter of 2.5 cm and thicknesses ranging from 50-600 micro m. The film has seven contact points defined by Pd electrodes for spectral response(SR) and I-V measurements. Measurements were done on the film with a visible light source. Numerical modeling helps us understand device properties and processes that take place in operation of the device.

The focus of this work was to identify loss mechanisms in photoresponse, reveal fundamental device properties, and develop a quantitative device model for MSM HgI₂ thin films using the DC Device modeling simulation tool MEDICI ™. The values for input parameters were chosen from literatutheory and reasonable estimates. Comprehensive studies were performed to investigate the sensitivity of SR and light I-V characteristics to each input parameter. Surface&Bulk recombinations have been investigated in this thesis. A Single, homogeneous region with all possible combinations of carrier mobilities, surface and bulk recombination parameters was not able to explain completely the measured SR. A Two-region model with the first region (0-0.5) μ m being surface&bulk recombination dominated, and the second (0.5-300) μ m bulk recombination dominated, was able to match the complete measured SR of current devices.

The key parameters determined from the simulations are the mobilities, bulk lifetimes and surface-recombination velocities at the front contact for both carriers. These are consistent with expectations based upon known single crystal properties

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