Small-signal deep level transient spectroscopy on hydrogenated amorphous silicon based metal/insulator/semiconductor structures

The high-temperature tail of small-signal deep level transient spectroscopy (DLTS) spectra of hydrogenated amorphous silicon (a-Si:H) based metal/insu lator/semiconductor structures has been analyzed in terms of oxidation of s ome negatively charged mobile hydrogen species at the Al/a-Si:H interface, the excitation pulses of an amplitude of 0.1 V being applied repetitively b etween the top Al and the bottom (gate) electrodes. The concentration of th e mobile hydrogen in the a-Si: H layer has been estimated to an amount up t o approximate to 2 x 10(20) cm(-3), taking the earlier published data on th e diffusion coefficient. Having chosen an appropriate polarity of the excit ation pulses, one could observe a DLTS peak moving with applied bias on the temperature axis. The latter is pointing to an energy distribution of stat es at the Al/a-Si: H interface. The interface state density increases with increasing energy depth of the states. At the ultimate experimentally obser vable energy of E approximate to 0.95 eV below the electron mobility edge E -c a corresponding areal density N-a(E) of these states amounted up to 1.5 x 10(11) cm(-2) eV(-1). (C) 1998 American Institute of Physics. [S0021-8979 (98)04224-8].