Resistive-switching and current conduction mechanisms have been studied in TiN/Ti/TiOx/HfOx/TiN resistive-switching random access memories (RRAMs). From I-V characteristics and temperature measurement, thermionic emission is found to be the most appropriate mechanism representing the dominant current conduction in all the bias regions and resistance states. Low-frequency noise power spectrum is measured to analyze accurately the conduction mechanism, which corroborates the thermionic-emission. Also, using the migration of oxygen ions depending on the polarity of the applied field, we propose the resistive-switching model of a double-layered RRAM to explain the unique resistive-switching characteristics.

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Traps and trap-related effects in recessed-gate normally-off AlGaN/GaN-based MOSHEMT with SiO 2 gate dielectric were characterized. Hysteresis in I D -V G was observed at elevated temperature (~120 o C) due to the traps. To understand the traps, current transient in drain was investigated at given gate and drain pulses with different temperatures. Two groups of time constants were extracted: one is nearly constant and the other is decreased with temperature. Extracted activation energies from the drain current transients with temperature are 0.66 eV and 0.73 eV, respectively, for given gate and drain pulses. Using extracted exponential trap density profile from frequency dependent conductance method [4], we could understand C-V behavior with frequency. It was shown that traps inside AlGaN layer are a main cause for the decrease of capacitance at high frequency in inversion region. The pulsed I-V characteristics also show frequency dependence. IntroductionThe AlGaN/GaN high electron mobility transistor (HEMT) is one of the strong candidates for next-generation power and microwave devices [1]. Recently, the metal-oxide-semi conductor heterostructure field-effect transistor (MOSHFET) using the recessed-gate was proposed to reduce the gate current and realize the normally-off characteristics [2]. However, problems of dispersion effects and instabilities due to the presence of traps still prevent the wide usage of this new device. Previously, various methods have been used to study the electrical traps in AlGaN/GaN HEMTs. However, relatively few studies have been made about the traps and trap-related effects in AlGaN/GaN MOSHFETs with a recessed-gate. In this paper, we investigate the traps and trap-related effects in recessed-gate AlGaN/GaN MOSHFETs using various characterization methods including the current transient spectroscopy, frequency dependent conductance method, C-V, and pulsed I-V [3], [4].

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