Alumina, Al2O3, layers as effective p-stops for silicon radiation detectors

Inter-strip shortening due to electron accumulation is a problem for any segmented p-type and double-sided n-type detectors. The standard approach for inter-strip or interpixel isolation is an implanted and annealed p-type layer, called p-stop. We show that alumina layer can be used as effective p-stops due to a negative surface charge at the silicon-alumina interface. We used ALD (atomic layer deposition) and e-beam evaporated alumina layers as inter-strip dielectrics for n-on-n strips. We fabricated a double sided strip detector (DSSD) on n-type silicon with alumina as a p-stop and tested the DSSD under gamma-ray irradiation. We compare ALD alumina layers with standard silicon oxide for isolating n-on-n strips. Equivalents to “p-stop” and “p-spray” were fabricated and evaluated with respect to their leakage currents. Finite element simulations support our experimental findings.