Space-Charge-Limited Photocurrents and Transient Currents in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mrow><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mi>Cd</mml:mi><mml:mo>,</mml:mo><mml:mi>Zn</mml:mi><mml:mo stretchy="false">)</mml:mo><mml:mi>Te</mml:mi></mml:mrow></mml:mrow></mml:math> Radiation Detectors
Katarina Ridzonova, Eduard Belas, Roman Grill, Jakub Pekarek, Petr Praus
Abstract
We combine steady-state photoconductivity and laser-induced transient current measurements under above-band-gap illumination to study space-charge formation in ($\mathrm{Cd},\mathrm{Zn})\mathrm{Te}$. Analytical and numerical models describing space-charge-limited photocurrents are developed and excellent agreement with measured data is obtained, especially with the Drift-diffusion model. A linear rise of photocurrent at low voltage is observed and ascribed to the trapping of injected holes in the region close to the cathode side. The influence of space-charge formation, the influence of photoconductive gain, and the contribution of shallow and deep levels to photocurrent-voltage characteristics are numerically simulated. According to measurements and calculations, recent principles used to evaluate detector properties, mainly the mobility-lifetime product, via the photoconductivity are critically assessed.