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The development of high resolution, room temperature semiconductor radiation detectors requires the introduction of
materials with increased carrier mobility-lifetime (μτ) product, while having a band gap in the 1.4-2.2 eV range. AlSb
is a promising material for this application. However, systematic improvements in the material quality are necessary to
achieve an adequate μτ product. We are using a combination of simulation and experiment to develop a fundamental
understanding of the factors which affect detector material quality. First principles calculations are used to study the
microscopic mechanisms of mobility degradation from point defects and to calculate the intrinsic limit of mobility from
phonon scattering. We use density functional theory (DFT) to calculate the formation energies of native and impurity point
defects, to determine their equilibrium concentrations as a function of temperature and charge state. Perturbation theory
via the Born approximation is coupled with Boltzmann transport theory to calculate the contribution toward mobility
degradation of each type of point defect, using DFT-computed carrier scattering rates. A comparison is made to measured
carrier concentrations and mobilities from AlSb crystals grown in our lab. We find our predictions in good quantitative
agreement with experiment, allowing optimized annealing conditions to be deduced. A major result is the determination
of oxygen impurity as a severe mobility killer, despite the ability of oxygen to compensation dope AlSb and reduce the net
carrier concentration. In this case, increased resistivity is not a good indicator of improved material performance, due to
the concomitant sharp reduction in μτ.
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