AVS 56th International Symposium & Exhibition
    Electronic Materials and Processing Thursday Sessions
       Session EM-ThA

Paper EM-ThA10
Self-annealing Effect in Neutron-Irradiated AlGaN/GaN High Electron Mobility Transistors

Thursday, November 12, 2009, 5:00 pm, Room B1

Session: Quantum Structures and Nitrides Devices
Presenter: G. Ko, Korea University, South Korea
Authors: G. Ko, Korea University, South Korea
F. Ren, University of Florida
S.J. Pearton, University of Florida
J. Kim, Korea University, South Korea
H.-Y. Kim, Korea University, South Korea
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AlGaN/GAN High Electron Mobility Transistors (HEMTs) have been studied due to their chemical and physical stability under harsh environments as well as high power and high frequency applications. Especially, AlGaN/GaN HEMT is considered as the potential candidate for space-based systems such as the space shuttles and the satellites. It is empirically known that displacement threshold energy (Ed) which is the energy required to displace an atom from its lattice position is inversely proportional to lattice constants. Since the lattice constant of GaN (a = 3.2496 Å) is smaller than Si (5.4301 Å) or GaAs (5.6533 Å), its radiation hardness is much better than these. Since neutron-induced effects on AlGaN/GaN heterostructures are not well known. We investigated self-annealing effect occurred in low-dose (< 1012 cm-2) neutron-irradiated AlGaN/GaN HEMT at room temperature. The device structure consisted of 25 nm AlGaN with 50 nm GaN cap layer on undoped 2 um GaN. These layers were grown on AlN buffer layer and c-plane sapphire by MOCVD. Ohmic metal was Ti/Al/Ni/Au and gate metal was Ni/Au. Neutron irradiation was performed with MC-50 cyclotron at Korea Institute of Radiological and Medical Sciences. Neutrons were generated when 35MeV protons collided with beryllium target occurring nuclear reaction. The average neutron energy was 9.8 MeV and the total fluence was 5.49 × 1011 cm-2. Electrical properties (Vds-Ids, Vgs-Igs, and transconductance) had been measured during 30 days after neutron irradiation. We could observe Vds-Ids drastically decrease for 7 days, which meant surface traps and deep traps were created in AlGaN/GaN HEMT. However its current level was gradually recovered after 7 days. And the recovery of transconductance and leakage current were also confirmed. This self-annealing effect can be attributed to the recombination of the created defects because the distance between the neighboring defects is very short. The defect clusters that are mobile at room temperature were created by neutron irradiation. The details about the irradiation and self-annealing will be presented.