Identification of Defect Levels in III-V Semiconductors Using Radioactive Isotopes

• Applicant: Privatdozent Dr. Manfred Deicher
• Subject Area: Condensed Matter Physics
• Term: from 2000 to 2003
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5257770

Spectroscopic techniques used in semiconductor physics like photoluminescence (PL) and Hall-effect that are able to detect and to characterize band gap states do not reveal information about their microscopic origin. To overcome this chemical "blindness" of the electrical and optical methods the present approach is to use radioactive isotopes as a tracer. Because of the characteristic concentration change according to the nuclear decay law, their involvement in the formation of electronic band gap states can be confirmed or denied definitely. Doping semiconductors with a variety of radioactive isotopes isotopically clean in a quantitatively controlled way is only realizable by ion implantation. GaN and its alloys with AlN and InN are one of the most interesting classes of materials in actual semiconductor research due to their potential as optoelectronic devices. The electrical activation of implanted dopants into these systems is more complex compared to other III-V compounds since this materials have both strong inter-atomic bonding demanding high annealing temperatures, and a constituent, N, having a high vapor pressure. An imperative prerequisite for these implantation studies is therefore the unambiguous identification of the PL signals and electrical properties related to potential doping atoms in GaN using radioactive isotopes of these dopants. An important class of intrinsic defects in many compound semiconductor of type AB like GaAs are antisites where an A atom is placed on a B site (AB) or vice versa. It is still an open question what the electronic levels of the GaAs antisite in GaAs are. A unique way to create GaAs antisite defects in GaAs in a controlled way and to avoid the introduction of any other defects during the production process is the transmutation of radioactive 71As to stable 71Ga. This transmutation can be followed up by PL and possibly created states in the band gap due to antisites can be clearly identified.

• DFG Programme: Research Grants