Electrical Characterization of Defects Introduced During Sputter Deposition of Schottky Contacts on n-type Ge

Abstract

The authors have investigated by deep level transient spectroscopy the electron traps introduced in n-type Ge during sputter deposition of Au Schottky contacts. They have compared the properties of these defects with those introduced in the same material during high-energy electron irradiation. They found that sputter deposition introduces several electrically active defects near the surface of Ge. All these defects have also been observed after highenergy electron irradiation. However, the main defect introduced by electron irradiation, the V-Sb center, was not observed after sputter deposition. Annealing at 250°C in Ar removed the defects introduced during sputter deposition.

Electrical characterization of defects introduced during metallization processes in n-type germanium

“…We also show that the concentrations of the most prominent EBDinduced defect, the V-Sb centre, depended on the metal deposited by EBD via the melting point of the metal and the influence thereof on the vacuum during metallization. We have found that sputter deposition also introduces several electrically active defects near the surface of Ge, but, contrary to what has been reported elsewhere [9], it did not introduce the V-Sb centre in our experiments. Most of the defects introduced by EBD and sputter deposition have also been observed after high-energy electron irradiation.…”

“…The fact that the E-centre is not observed after sputter deposition in our system may imply that our sputter process does not introduce a sufficient number of single vacancies at and close to the surface that can diffuse into the Ge and combine with Sb ions to form V-Sb, as in the case of EBD. It should be realised that most of the damage that we observe after sputter deposition is caused by backscattered neutral Ar ions that, for the sputter conditions used here, have a maximum energy of approximately 700 eV of RF power [9]. From TRIM [14] modelling we have found that the range and straggle of these ions are 2.1 and 1.2 nm, respectively.…”

“…In a different system Au Schottky contacts were sputter deposited onto similar Ge samples cut from the same wafer. For sputter deposition Ar was leaked into the system to a pressure of 6 Â 10 À2 mbar [9]. The sputterdeposited contacts were deposited at a rate of about 2 nm s À1 and were 400 nm thick.…”

“…Unfortunately, these latter two methods introduce defects in semiconductors. Some investigations regarding the defects introduced in Ge during EBD [6][7][8] and sputter deposition [9,10] have been reported. The defects introduced during these processes reside in the Ge at and close to the metal-Ge junction; they influence device performance and alter the barrier heights of the contacts [11].…”

Electrical characterisation of ruthenium Schottky contacts on n-Ge (100)

“…Defects introduced in Ge during metallization processes have been investigated [11,26,27,28,29,30,31].…”