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

Journal of Electronic Materials (Impact Factor: 1.64). 11/2007; 36(12):1604-1607. DOI: 10.1007/s11664-007-0245-y

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 high-energy 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.

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    ABSTRACT: We have used deep level transient spectroscopy (DLTS), and Laplace-DLTS to investigate the defects created in antimony doped germanium (Ge) by sputtering with 3keV Ar ions. Hole traps at EV+0.09eV and EV+0.31eV and an electron trap at EC−0.38eV (E-center) were observed soon after the sputtering process. Room temperature annealing of the irradiated samples over a period of a month revealed a hole trap at EV+0.26eV. Above room temperature annealing studies revealed new hole traps at EV+0.27eV, EV+0.30eV and EV+0.40eV.
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    ABSTRACT: Schottky barrier diodes prepared by electron beam deposition (EBD) on Sb-doped n-type Ge were characterized using deep level transient spectroscopy (DLTS). Pt EBD diodes manufactured with forming gas in the chamber had two defects, E0.28 and E0.31, which were not previously observed after EBD. By shielding the samples mechanically during EBD, superior diodes were produced with no measureable deep levels, establishing that energetic ions created in the electron beam path were responsible for the majority of defects observed in the unshielded sample. Ge samples that were first exposed to the conditions of EBD, without metal deposition (called electron beam exposure herein), introduced a number of new defects not seen after EBD with only the E-center being common to both processes. Substantial differences were noted when these DLTS spectra were compared to those obtained using diodes irradiated by MeV electrons or alpha particles indicating that very different defect creation mechanisms are at play when too little energy is available to form Frenkel pairs. These observations suggest that when EBD ions and energetic particles collide with the sample surface, inducing intrinsic non-localised lattice excitations, they modify defects deeper in the semiconductor thus rendering them observable.
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    ABSTRACT: Low energy(+-80 eV) Ar plasma etching has been successfully used to etch several semiconductors, including GaAs, GaP, and InP. We have studied the only prominent defect, E0.31, introduced in n-type Sb-doped Ge during this process by deep level transient spectroscopy (DLTS). The E0.31 defect has an energy level at 0.31eV below the conduction band and an apparent capture cross-section of 1.4� x 10e�14 cm2. The fact that no V–Sb defects and no interstitial-related defects were observed implies that the etch process did not introduce single vacancies or single interstitials. Instead it appears that higher order vacancy or interstitial clusters are introduced due to the large amount of energy deposited per unit length along the path of the Ar ions in the Ge. The E0.31 defect may therefore be related to one of these defects. DLTS depth profiling revealed the E0.31 concentration had a maximum (6�x10e13 /cm�3) close to the Ge surface and then it decreased more or less exponentially into the Ge. Finally, annealing at 250 C reduced the E0.31 concentration to below the DLTS detection limit.
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