Defect assessment and leakage control in Ge junctions

• The impact of electrically active defects on the electrical characteristics of Ge in STI Si diodes has been investigated.
• The presence of threading dislocations and associated deep acceptors has a marked impact on the electrical characteristics.
• The DLTS response is related to electron repulsive centers located at ∼0.33–0.40 eV below the conduction band.

In this work, the temperature behavior of the transport mechanisms present in Ge p+n junctions selectively grown in shallow trench isolation (STI) substrates is investigated. Special attention is given to the impact of electrically active defects on the current–voltage (I–V) and capacitance–voltage (C–V) characteristics. Moreover, deep level transient spectroscopy (DLTS) is performed in order to evaluate the electrical properties of the traps. The results show that the presence of threading dislocations and associated deep acceptors has a marked impact on the electrical characteristics. The DLTS response seems to be related to electron repulsive centers with an acceptor character located at ∼0.33–0.40 eV below the conduction band. This mid-gap position yields very effective Shockley–Read–Hall centers and can explain the generation lifetime reduction and leakage increase observed in non-annealed Ge in STI Si diodes.

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