Papers by Keyword: Electron Trapping

Abstract: Current-voltage characterization and thermal dielectric relaxation current (TDRC) measurements are carried out on 4H silicon carbide (SiC) n-channel MOSFETs processed with different post oxidation anneals (POAs) in O₂, N₂O, and NO atmospheres at high temperature. In all samples we observe a distinct peak at a temperature of 70 K in the TDRC spectra due to a defect close to the conduction band of 4H-SiC having a high density of states (>10¹³ cm^-2eV^-1). We show that this defect is related to the degradation of the device performance such as the MOSFET conductivity. Comparing the different POAs, NO strongly reduces the density of states close to the conduction band and thus increases the amount of free channel electrons. Based on TDRC measurements we want to suggest a method for more accurate estimation of the true channel mobility accounting for the reduced channel electron density due to trapping.

Abstract: We study the threshold voltage (V_th) instability of commercially available silicon carbide (SiC) power MOSFETs or prototypes from four different manufacturers under positive bias temperature stress (PBTS). A positive bias near the V_th causes a threshold voltage shift of 0.7 mV per decade in time per nanometer oxide thickness in the temperature range between-50 °C and 150 °C. Recovery at +5 V after a 100 s +25 V gate-pulse causes a recovery between-1.5 mV/dec/nm and-1.0 mV/dec/nm at room temperature and is decreasing with temperature. All devices show similar stress, recovery and temperature dependent behavior indicating that the observed V_th instabilities are likely a fundamental physical property of the SiC-SiO₂ system caused by electron trapping in near interface traps. It is important to note that the trapping is not causing permanent damage to the interface like H-bond-breakage in silicon based devices and is nearly fully reversible via a negative gate bias.

Abstract: We report on the threshold voltage () instability under operating conditions after gate bias switches at constant drain voltage for n-MOSFETs fabricated on 4H silicon carbide (4H-SiC). This effect occurs at room temperature and close to the of the device. We show that the origin of the instability is electron trapping into SiO₂ over an energy barrier of (0.3-0.4) eV. These traps show similarities to traps previously observed in 4H-SiC MOS capacitors and labelled near interface traps (NITs). Further, the density of the traps can be reduced by one order of magnitude through post-oxidation annealing in nitric oxide atmosphere.

Abstract: Temperature dependent capacitance-voltage (C-V) and constant capacitance transient spectroscopy (CCDLTS) measurements have been performed to investigate the role of N in improving the transport properties of 4H-SiC MOS transistors. The higher channel mobility in the N pre-implanted transistors is due at least in part to activation of a small fraction of the implanted N near the SiO₂/SiC interface as donors in SiC during oxidation, thus reducing the effects of interface trapping. In addition, the absence of oxidation-induced near-interface defects, which were observed in NO-annealed capacitors, may contribute to the improved mobility in N pre-implanted transistors.

Abstract: A novel electron trapping material of CaB₄O₇:Sm³⁺ was synthesized by high temperature solid-state reaction, and its characterization and luminescent properties were investigated at room temperature. The results indicate that ultraviolet light can be used as exciting source to store energy. After exposed under ultraviolet, the sample was stimulated by 980nm laser. As a result, an obvious luminescence at 556, 596 and 643 nm were detected. The photo-stimulated emission spectrum was three bands peaking at 562, 599 and 646 nm that are the characteristic emission of Sm³⁺ ions due to the f→f transitions ⁴G_5/2→⁶H_J (J = 5/2, 7/2, 9/2), respectively. The TL glow curve contains two overlapping glow peaks at around 541 and 598 K.was synthesized by high temperature solid-state reaction, and its characterization and luminescent properties were investigated at room temperature. The results indicate that ultraviolet light can be used as exciting source to store energy. After exposed under ultraviolet, the sample was stimulated by 980nm laser. As a result, an obvious luminescence at 556, 596 and 643 nm were detected. The photo-stimulated emission spectrum was three bands peaking at 562, 599 and 646 nm that are the characteristic emission of Sm3+ ions due to the f→f transitions 4G5/2→6HJ (J = 5/2, 7/2, 9/2), respectively. The TL glow curve contains two overlapping glow peaks at around 541 and 598 K.