AVS 52nd International Symposium
    Electronic Materials and Processing Thursday Sessions
       Session EM2-ThA

Invited Paper EM2-ThA1
Narrow Band Gap Group III-Nitrides

Thursday, November 3, 2005, 2:00 pm, Room 310

Session: Dilute Nitrides and Small Bandgap Semiconductors
Presenter: W. Walukiewicz, Lawrence Berkeley National Laboratory
Correspondent: Click to Email
Incorporation of small amounts of N into group III-V semiconductors leads to a dramatic reduction of the band gap of resulting IIIN@sub x@V@sub 1-x@ alloys. This effect can be well described by the Band Anticrossing (BAC) model that considers the interaction between localized states of N and the extended conduction band states. The interaction splits the conduction band into two nonparabolic bands, resulting in large changes in the electrical and optical properties of these materials. The BAC model provides a consistent and quantitative description of experimentally observed data including the large band gap bowing, splitting of the conduction band, and increase of the electron effective mass. Comprehensive studies of the electronic structure and electrical and optical properties of InN and In-rich In@sub 1-x@Ga@sub x@N alloys will also be discussed. In addition to having a narrow gap (0.7 eV), InN also has an extremely high electron affinity of 5.8 eV, placing the conduction band edge of this material 0.9 eV below the average energy of dangling bond defects (Fermi level stabilization energy, E@sub FS@). This unusual band alignment has profound consequences for the behavior of dopants and defects and explains the extreme proclivity of InN and In-rich group III-nitride alloys for n-type conduction. As grown, undoped InN is always n-type with electron concentrations ranging from mid 10@super 17@ cm@super -3@ to as high as 10@super 21@ cm@super -3@. We show that similar range of electron concentrations can be achieved by irradiation of thin InN films with 2 MeV He@super +@ ions.