Impact of low dose gamma irradiation on electronic carrier transport in AlGaN/GaN High Electron Mobility Transistors
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Impact of low dose gamma irradiation on electronic carrier transport in AlGaN/GaN High Electron Mobility Transistors Anupama Yadav1, Elena Flitsiyan1, Leonid Chernyak1, Fan Ren2, Stephen J. Pearton3, Jerry Wayne Johnson4, and Igor Lubomirsky5 1
Department of Physics, University of Central Florida, Orlando, Florida 32816, USA Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611, USA 3 Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32606, USA 4 IQE KC LLC, Taunton, Massachusetts 02780, USA 5 Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel 2
ABSTRACT AlGaN/GaN High Electron Mobility Transistors were exposed to 60Co gamma-irradiation to doses up to 300Gy. The impact of Compton- electron injection (due to gamma-irradiation) is studied through monitoring of minority carrier transport using Electron Beam Induced Current (EBIC) technique. Temperature dependent EBIC measurements were conducted on devices before and after exposure to the irradiation, which provide us with critical information on gamma-irradiation induced defects in the material. As a result of irradiation, minority carrier diffusion length increases significantly, with an accompanying decrease in the activation energy. This is consistent with the longer life time of minority carrier in the material’s valence band as a result of an internal electron injection and subsequent trapping of Compton electrons on neutral levels. INTRODUCTION GaN based devices have strong potential applications for the high power, high frequency and high temperature electronic [1]. The large band gap discontinuity and reduced lattice mismatch between GaN and its ternary alloy AlGaN allows for the fabrication of a high quality AlGaN/GaN heterostructures that can confine a high density of electrons in a two dimensional electron gas. It is known that structural defects can strongly affect the electrical and optical properties of semiconductor devices. Thus the AlGaN/GaN High Electron Mobility Transistors (HEMTs) have been intensively investigated because of its high tolerance to radiation induced degradation [2,3]. While studies of radiation induced defects in GaN based devices have attracted significant interest, information concerning the response of AlGaN/GaN based HEMTs to gamma-irradiation is restricted to a few reports. This lack of information, together with the apparent discrepancies in the effects induced by the exposure to energetic gamma-rays highlight the need for further investigation. Understanding the defects arising under irradiation not only going to provide the new information about the charge carrier transport and polarization effect in such devices but will provide a substantial information for improving device performance. In the present communication, we discuss the radiation induced electronic carrier transport properties of AlGaN/GaN based HEMTs.
EXPERIMENT The HEMT were grown on Si wafers by Metal Organic Chemical Vapor Deposition (MOCVD
