Advances in the High-pressure Crystal Growth Technology of Semi-insulating CdZnTe for Radiation Detector Applications

摘要

The properties of large diameter (140 mm) semi-insulating Cd_(1-x)Zn_xTe (x = 0.1) ingots grown by the vertical High-Pressure Electro-Dynamic Gradient (HP EDG) technique are discussed. The HP EDG crystal growth technology recently developed and introduced at eV PRODUCTS significantly improves the downstream CdZnTe detector fabrication yield compared to earlier versions of the HP crystal growth technology. These yield improvements stem from the improved structural and charge transport properties of the HP EDG CdZnTe ingots. Improvements were achieved in three areas: a) reduced thermal stress in the ingots, b) improved single crystal yield, and c) improved electron transport properties. The new state-of-the-art HP EDG crystal growth systems offer exceptional flexibility, thermal and mechanical stability and allow the growth of high purity CdZnTe materials. The flexibility of the multi-zone heater system allows the dynamic control of heat flow to optimize the growth-interface shape during crystallization. This flexibility combined with an advanced control system, improved system diagnostics and realistic thermal modeling provides an excellent platform for further process development. Results on the initial HP EDG CdZnTe ingots grown with low temperature gradient show the complete elimination of ingot cracking. The increased single crystal yield combined with the unproved electron transport properties allows the fabrication of large-volume electron-only devices at higher yield. The CdZnTe ingots regularly contain sections with electron mobility-lifetime product μτ_e≥ 5.0x10~(-3) cm~2/V and occasionally yield material with μτ_e ≥ 8.0x10~(-3) cm~2/V.