Deep Level Defects in Indium Phosphide PIN Diodes

Deep level defects in Zinc diffused InP PIN diodes are characterized using deep level transient spectroscopy (DLTS) and low frequency noise (LFN) measurement. By using the DLTS technique, two deep traps are revealed. The first is located 0.11 eV above the valence band edge, and is localized near the edge of the depletion region in the p+ region. The second trap is found to be 0.3 eV below the conduction band, and is distributed spatially throughout the depletion region. Both of these traps have been reported previously; they are related with Zinc diffusion. By measuring the low frequency noise spectrum under forward bias, four generation-recombination centers are revealed during a temperature scan from 100 K to 400 K. The activation energy of the observed traps were found to be 0.20 eV, 0.25 eV, 0.31 eV, and 0.54 eV. Although the types of these deep centers (i.e., electron or hole trap) cannot be unambiguously determined using this method, the trap at 0.31 eV is most likely the same 0.3 eV electron trap found in DLTS, since they represent the similar time constants in the same temperature range; likewise, the deep center with activation energy of 0.54 eV has also been observed as an electron trap before, and is believed due to antisite defects such as indium vacancies or phosphorus interstitials. The other two centers at 0.20 eV and 0.25 eV have also been previously reported as electron traps, but the origins are as yet unclear. The demonstration of the ability to detect known states by both DLTS and LFN enables exploration of defects in other material systems in the future.