Infrared Properties of 40–60 MeV Electron-Irradiated Germanium

The infrared properties of germanium containing low oxygen concentration (<1016 cm−3) and high oxygen concentration (>1017 cm−3) have been studied after irradiation at T≤25°C by 40- to 60-MeV electrons. One cold-temperature irradiation at 125°K was also performed on a high oxygen concentration germanium sample. The germanium samples that were n type initially exhibit p-type infrared properties in the 2- to 8-μ wavelength range after being converted to p type by the irradiation. Germanium containing high oxygen concentration exhibits new vibrational bands in the 9- to 16-μ wavelength range which are associated with oxygen-defect complexes. No radiation-induced bands from 9 to 16 μ are observed in oxygen-free germanium. Detailed isochronal annealing experiments (up to ∼700°K) were performed on all samples. Strong evidence is given which shows that one of the oxygen vibrational bands induced in germanium (at 618 cm−1) appears to be a single oxygen atom plus a vacancy defect which corresponds to the comparable defect found in silicon, namely the silicon A center.