Methodology for evaluation of mobility-lifetime product by spectroscopy measurements in CdZnTe spectrometers

Abstract

A novel methodology is presented for extraction of the semiconductor electron and hole mobility-lifetime products by x- and γ-ray spectroscopy analysis. The methodology is based on the analysis of spectroscopy results, namely the maximal and the average charge collection efficiencies as discussed below, for different photon energies at various bias voltages. The methodology enables the evaluation of both electron and hole mobility-lifetime products without the need to use α particle measurements. The evaluation is carried out by a single parameter fitting of the models analyzed in this study. Mobility-lifetime products for CdZnTe substrates grown by Bridgman and high pressure Bridgman (HPB) methods are reported and compared. Typical values of μe⋅τe=2⋅10−3 and μh⋅τh=1⋅10−5 cm2/V are extracted for HPB grown CdZnTe with 10% Zn concentration. Values of μe⋅τe=9⋅10−4 and μh⋅τh=1⋅10−7 cm2/V are obtained for CdZnTe with 10% Zn concentration grown by the Bridgman method.

Time-of-Flight Measurements on TlBr Detectors

“…2. A trapping time constant is defined by using the trap concentration , its capture cross section , and thermal velocity of carrier th as (1) Assuming the detailed balance between the trapped and conduction states, the detrapping time constant is related to as (2) where is the effective density of states in the conduction band, is the trap ionization energy, is the Boltzmann constant and is the absolute temperature of the crystal. Therefore, in shallow traps with energy equal to or even slightly larger than , the detrapping time can be shorter than the corresponding trapping time provided that .…”

“…Because the detection property largely depends on the carrier transport properties, accurate evaluation of the parameters such as mobility ( ) and trapping lifetime ( ) plays a crucial role in detector development. The transport properties of the detector materials are usually evaluated by a product of because of the ease of determining this value from the detection property itself without any special measurements [1], [2]. However, to improve transport properties, accurate and independent determination of the drift mobility from the corresponding trapping time is very important.…”

A modeling method to calibrate the interaction depth in 3-D position sensitive CdZnTe gamma-ray spectrometers

“…Thc mobility of holes p~h is about an order ofmagnitudc smaller than pe, so in the modcling pli is simply assumed to he 100 Thc measurement of the mobility-lifetime product of holes (fir)* is difficult in CdZnTe detectors because ( p r ) h is much smaller than (pr), [6]. for (~7 )~ and ( p r ) h , the cathode pulse heights for the photoclcctric events can he calculated for each interaction dcpth using Eqns.…”

Direct determination of the mobility-lifetime (μτ) product from the transient response of extrinsic Ge:Ga photoconductors

“…This is a key transport parameter that depends on both majority and minority doping. Mobility-lifetime products are commonly measured by individual measurements of l and s (Hall effect, Haynes-Shockley, photo-Hall experiments), or with alpha or other types of spectroscopy in high-energy radiation detector materials [3,4].…”