DETECTION OF NEAR-SURFACE DEFECTS IN SEMICONDUCTORS BY DEEP-LEVEL TRANSIENT SPECTROSCOPY

The detection of defects at and close to the interface of a Schottky barrier diode by deep-level transient spectroscopy (DLTS) is influenced by several factors, including the position and shape of the Fermi level at the interface, the measurement temperature and the free-carrier density of the semiconductor. In this article it is shown that in order to optimize the detection of near-surface defects by DLTS, the application of a filling pulse with an appropriate amplitude is of cardinal importance. The results presented for subthreshold electron irradiation and low-energy Ar-ion sputtering of GaAs indicate that, in order to detect defects with shallow energy levels by DLTS in the interface region, the Schottky diode should be forward biased to at least flatband condition. Further, to maximize the DLTS signal of these defects, a DLTS filling pulse extending several volts into forward bias may have to be applied.