Electronic and annealing properties of the E0.31 defect introduced during Ar plasma etching of germanium

Abstract

Low energy (7 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 Sbdoped Ge during this process by deep level transient spectroscopy (DLTS). The E0.31 defect has an energy level at 0.31 eV below the conduction band and an apparent capture cross-section of 1.4 10 14 cm 2 . 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 10 13 cm 3 ) close to the Ge surface and then it decreased more or less exponentially into the Ge. Finally, annealing at 2501C reduced the E0.31 concentration to below the DLTS detection limit.