14-03-2017 14:30  Guest Lecture

Effects of Electron Injection in Wide Band Gap Semiconductors: Physics and Applications

It has been recently discovered that electron injection into (Al)GaN doped with Magnesium, Manganese, Carbon, and Iron using either electron beam of a Scanning Electron Microscope or a forward bias application to p-n junction or Schottky barrier, leads to a multiple-fold increase of minority carrier diffusion length and lifetime. It has also been demonstrated that forward biasing a GaN-based photovoltaic detector results in a several-fold responsivity enhancement due to a longer minority carrier diffusion length in the detectors Mg-doped p-region as a result of electron injection. The observed electron injection effects were attributed to the charging of the meta-stable centers associated with the above-referenced impurities. The systematic optical and electrical studies were carried out on the representative range of GaN and AlGaN samples to determine the activation energy for the effects of electron injection. For (Al)GaN doped with Mg, the activation energy is close to the thermal ionization energy of the Mg-acceptor and increases consistent with increasing Al content in the lattice. In the case of Mn-doped GaN, electron-beam induced excitation from the Mn3+ neutral acceptor state was demonstrated to thermalize with an activation energy of 360 meV. The activation energy of the electron injection effects for GaN doped with Carbon and Iron are also consistent with the previously reported defect states in the band gap. Finally, the results on minority carrier transport and electron injection-induced effects in ZnO doped with phosphorus (P) and antimony (Sb) will be presented. As for Nitrides, the activation energy for the electron trapping effects in ZnO is consistent with deep P- and Sb-acceptor thermal ionization energy and is found to be about 200 meV. Device application of the electron injection effects will be also demonstrated for ZnO-based photovoltaic detectors. For biography and publications follow the link: https://physics.cos.ucf.edu/people/chernyak-leonid/

Location: 1003
Speaker: Professor Leonid Chernyak
Affiliation: University of Central Florida Physics Department Back