Transport Imaging of Spatial Distribution of Mobility-Lifetime (Micro Tau) Product in Bulk Semiconductors for Nuclear Radiation Detection
Abstract
The objective of this research is to advance the development of a micro-analysis technique for characterizing the charge transport properties in bulk semiconductor materials for room temperature nuclear radiation detection. The technique is applied to bulk semi-insulating thallium bromide (TlBr) and cadmium zinc telluride (CZT) and uses a two-dimensional diffusion model and transport imaging to make rapid contact-free measurements of the magnitude and spatial variation in the mobility-lifetime (mu tan) product at 2 m resolution. The g product is a key measure of charge transport, and a uniform g product is critical for optimum energy resolution in gamma ray detectors. Spatial variations in the ambipolar diffusion length are observed in TlBr on a scale of ~10 m, and the cathodoluminescence (CL) spectrum in TlBr at 5 K is reported. Using CL and photo-induced conductivity transient spectroscopy (PICTS), an empirical energy level diagram for Se and Pb defect levels in TlBr is reported. The g product in TlBr is generally found to decrease with increasing impurities/defects. The mu tan product in TlBr and CZT is found to decrease with increasing temperature over the ranges of 8 K V 102 K and 5 K V 60 K, respectively. Transport imaging is applied for the first time to investigate the effects of Te inclusions in CZT and the role of photon recycling in TlBr and CZT.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2012
- Accession Number
- ADA563779
Entities
People
- David J. Phillips
Organizations
- Naval Postgraduate School