10.
Positron-lifetime experiments have been carried out on two undoped
n-type liquid encapsulated Czochralski (LEC)-grown InP samples with different stoichiometric compositions in the temperature range 10-300 K. For temperatures below 120 K for P-rich InP and 100 K for In-rich InP, the positron average lifetime began to increase rapidly and then leveled off, which was associated with the charge state change of hydrogen indium vacancy complexes from (
VInH
4)
+ to (
VInH
4)
0. This phenomenon was more obvious in P-rich samples that have a higher concentration of
VInH
4. The transformation temperature of approximately 120 K suggests that the complex
VInH
4 is a donor defect and that the ionization energy is about 0.01 eV. The ionization of neutral
VInH
4 accounted for the decrease of the positron average lifetime when the sample was illuminated with a photon energy of 1.32 eV at 70 K. These results provide evidence for hydrogen complex defects in undoped LEC InP.
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