An effective electrical isolation scheme by iron implantation at different substrate temperatures

Abstract

Abstract-High-energy implantation of iron in n-type doped InP epilayers at different substrate temperatures: 77K, room temperature (RT), 100 0 C and 200 0 C was investigated to study the electrical isolation of n-type InP. Iron isolation implants were performed at 1MeV with a fluence of 5x10 14 /cm 2 . This isolation scheme was chosen to place most of the iron atoms well inside the n-type doped layer. The sheet resistivity (R s ), sheet carrier concentration (n s ) and sheet mobility (µ) were measured as a function of substrate temperature and post-implantation annealing temperature (100 -800 0 C). Samples implanted at 77K, RT and 100 0 C show more or less the same trend of postimplant annealing characteristics. A maximum sheet resistivity of ~1x107 Ω/‫ڤ‬ was achieved for samples implanted at 77K, RT and 100 0 C after annealing at 400 0 C. A lower resistivity of ~1x106 Ω/‫ڤ‬ was obtained for a 200 0 C implant after annealing at 400 0 C. Lower damage accumulation due to enhanced dynamic annealing is observed for the highest implantation temperature. For 200 0 C substrate temperature, annealing above 400 0 C resulted in a gradual decrease in sheet resistivity to a value close to that of the starting material. But this is not the case for the lower substrate temperatures.The sheet resistivity was increased again for 77K, RT and 100 0 C implant after annealing at 600 0 C. We infer that for 77K, RT and 100 0 C implantation temperatures, the electrical isolation is due to a product of both damage related centers and defects related to the presence of Fe whereas for 200 0 C substrate temperature, we infer that only damage induced compensation removes the carriers. These results show the importance of iron implants as a device isolation scheme.