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We focus on slow de-trapping phenomena in AlGaN/GaN MIS-HEMTs with a bilayer dielectric ( in-situ Si 3 N 4 /Al 2 O 3 ) with two different thicknesses of in-situ Si 3 N 4 (10 nm and 5 nm). By using a “filling pulse” at a positive gate voltage, a trap with activation energy of 0.69–0.7 eV was identified to be responsible for the V TH shift. Based on literature, filling conditions, and the simulated band diagrams, this trap is most probably located at the interface between the dielectrics and AlGaN barrier. A physical model is proposed to explain the V TH shift due to the trapping/de-trapping phenomena based on the occupation dynamics of donor traps at the interface between the in-situ Si 3 N 4 /Al 2 O 3 and the AlGaN barrier. [ABSTRACT FROM AUTHOR]

The reliability of Au-free Ohmic contacts has been evaluated under a constant current stress (500 mA/mm) in a high temperature environment (150 °C, 175 °C, and 200 °C). Two Ohmic contact schemes with different Ti/Al thicknesses (5 nm/100 nm and 10 nm/100 nm) have been tested. The results showed that the degradation of the resistance ( R increase ) is accelerated at a higher temperature condition. Moreover, R increase has a square root dependence with the time. This indicates that a diffusion process could be responsible for the observed degradation. This has been confirmed by means of physical failure analyses (FIB/TEM) performed on a highly degraded device: an apparent roughness of the interface between TiN and the Ohmic metal layer was observed. On top of this, Nitrogen out-diffusion into the Ohmic metal was observed in the EDS/EELS analyses, suggesting that a material diffusion phenomenon might play a role. In addition, we observed that the devices with a lower initial contact resistance ( R c ) showed lower degradation with respect to devices with a larger initial R c . This suggests that obtaining lower R c is beneficial not only for the performance but also for the reliability. [ABSTRACT FROM AUTHOR]

Insulin-like growth factors (Igf1 and Igf2) play a key role in growth and development of vertebrates. In mammals, the expression of IGF s is regulated by estradiol-17β (E 2) via estrogen receptors (ESRs). The expression of igf s can also be regulated by E 2 in fish, while comparative study of this is still lacking. The present study examined tissue distribution of igfs and hepatic expression of igf s and esr s during gonad development in Scatophagus argus by real-time PCR. Serum E 2 concentration was measured by enzyme-linked immunosorbent assay (ELISA). The hepatic expression of igf s and esr s at gonadal phase III, incubated with either E 2 (0.1, 1 or 10 μM) alone or in combination with estrogen receptor antagonists-fulvestrant, MPP or PHTPP, was measured. igf1 and igf2 expressed highest in liver of both sexes. Igf1 , esr1 and esr2b expressions and serum E 2 concentration increased, while igf2 and esr2a expressions decreased, during ovary development. Igf s and esr s expressions increased while serum E 2 concentration maintained low during testis development. In females, E 2 incubation enhanced the expressions of igf1 and esr1 but inhibited that of igf2 and esr2a. Both fulvestrant and MPP inhibited up-regulation effect of E 2 on igf1 and esr1. Fulvestrant enhanced down-regulation effect of E 2 on igf2 and esr2a , but MPP conversely. In males, E 2 incubation enhanced the expressions of igf s, esr1 and esr2a. Fulvestrant and MPP inhibited up-regulation effect of E 2 on igf s and esr1. PHTPP inhibited igf1 and esr2 expressions in both sexes. Our results indicated that the expression of igfs is regulated by E 2 via Esrs in S. argus. Unlabelled Image • igf1 and igf2 was found to be expressed highest in the liver of both sexes in S. argus. • There is a correlation between the expression of igf s, esr s and serum E 2 concentration in S. argus. • It was first found in fish that E 2 regulates the expression of igf s via Esrs. • E 2 regualates the expression of igf1 via both Esr1 and Esr2 in female and male S. argus. • E 2 regualates the expression of igf2 via Esr2a and Esr1 in female and male S. argus , respectively. [ABSTRACT FROM AUTHOR]

Effects of oxidation and nitric oxide (NO) post-oxidation annealing (POA) processes on the gate oxide integrity on 4H-SiC are investigated. Interface state density, flatband voltage, electron tunneling barrier height, breakdown field, and time-dependent dielectric breakdown are extracted. With the same NO POA condition, more nitrogen atoms are incorporated into wet oxide than dry oxide. The interface state density can be passivated effectively. At the same time, the electron tunneling barrier height at the SiO 2 /SiC interface approaches the ideal barrier height while positive charges would be introduced in oxide. NO annealing does not affect the breakdown field significantly. Regarding the time-dependent dielectric breakdown (TDDB) reliability, with increasing NO annealing time, the 10-year-projected intrinsic breakdown field decreases. It is concluded that NO annealing is effective in reducing the density of interface traps and hole traps originated from carboxyl defects, but excessive amount of nitrogen will turn into hole traps and thus deteriorates TDDB performance. • With the same NO POA condition, more nitrogen atoms are incorporated into wet oxide than dry oxide. • With nitrogen incorporation, the interface state density can be passivated effectively. • Wet oxidation results in slightly higher breakdown field while NO POA slightly reduces the breakdown field • With increasing NO annealing time, the 10-year-projected intrinsic breakdown field decreases for both wet and dry oxidation samples. • Excessive amount of nitrogen will turn into hole traps and thus deteriorates TDDB reliability of gate oxide on 4H-SiC. [ABSTRACT FROM AUTHOR]

The aim of achieving E-mode operations has led to the proposal of novel hybrid ferroelectric charge trap gate stack schemes. These schemes involve utilizing a combination of the charge trapping layer (CTL) and the ferroelectric laminated layer to positively shift the threshold voltage to a normally-off margin after initializing the gate pulse, thus achieving the Enhancement-mode (E-mode) characteristic. This study focuses on the forward gate bias time-dependent dielectric breakdown (TDDB) gate reliability in the E-Mode GaN MIS-HEMTs using ferroelectric charge trap gate stack (FEG-HEMT) with and without recess and investigates the impact of temperature on TDDB. The gate voltages required for operation with a 1 % failure rate over a 10-year period are 12.95 V and 10.22 V at 25 °C and 150 °C for both samples, respectively. Also, the examination of the stability of the recessed process by calculating the activation energies (0.7 eV) of both samples are demonstrated. The article also investigates the relationship between long-term reliability and short-term initialization by examining the transition point of the time-dependent failure curve. • The aim of achieving E -mode operations has led to the proposal of novel hybrid ferroelectric charge trap gate stack schemes. • This study focuses on the forward gate bias time-dependent dielectric breakdown (TDDB) gate reliability in the E-Mode GaN MIS-HEMTs using ferroelectric charge trap gate stack (FEG-HEMT) • The gate voltages required for operation with a 1% failure rate over a 10-year period are 12.95V and 10.22V at 25°C and 150°C for both samples, respectively. • Also, the examination of the stability of the recessed process by calculating the activation energies (0.7eV) of both samples are demonstrated. [ABSTRACT FROM AUTHOR]

In this work, the time-dependent dielectric breakdown (TDDB) analysis is performed to understand the gate oxide reliability in SiC MOSFETs with two different structures, i.e., planar and trench gate structures. We have discovered different gate leakage current behaviors between the SiC MOSFETs with planar gate (Sample A) and trench gate (Sample B) during the forward gate bias stress. Notably, the slight increase of the gate current during the stress and the negative activation energy (E a = −0.07 eV) observed in Sample A suggest that the hole generation caused by the impact ionization can be occurred during the forward gate TDDB tests. Furthermore, the SiC MOSFETs with trench gate structure (Sample B) exhibit the operation voltage of 55.7 V (exponential law) and 57.3 V (power law) for the 0.001 % failure of 30 years under 175 °C, indicating that SiC trench gate MOSFETs with enough thick gate dielectric (87.1 nm (bottom) and 77.9 nm (sidewall)) can have the promising forward gate TDDB stability. • The time-dependent dielectric breakdown (TDDB) analysis is performed to understand the gate oxide reliability in SiC MOSFETs • Different gate leakage current behaviors between the SiC MOSFETs with planar gate and trench gate • The negative activation energy observed in SiC planar MOSFETs suggests that the hole generation caused by the impact ionization • SiC trench gate MOSFETs with enough thick gate dielectric can have the promising forward gate TDDB stability. [ABSTRACT FROM AUTHOR]

Abstract Phoenixin (Pnx), a recently discovered neuropeptide, has been implicated in reproduction. Pnx mainly exists in two active isoforms, phoenixin-14 (Pnx-14) and phoenixin-20 (Pnx-20). However, little is known about the functions of Pnx in teleosts. To determine the roles of Pnx in the regulation of reproduction in Scatophagus argus , the physiological characterization of the Pnx was analyzed. During ovary development, the expression of pnx in phase IV was higher than in phase II and III in the hypothalamus. In the pituitary, pnx expression was highest in phase IV, moderate in phase III, and lowest in phase II. When hypothalamus and pituitary fragments were cultured in vitro with Pnx-14 and Pnx-20 (10 nM and 100 nM) for 6 h, the expression of GnRHR (gonadotropin releasing hormone receptor), lh (luteinizing hormone) and fsh (follicular stimulating hormone) in the pituitary increased significantly, except GnRH (gonadotropin releasing hormone) in the hypothalamus. Similarly, the expression of GnRHR , lh and fsh in the pituitary increased significantly after injecting S. argus with Pnx-14 and Pnx-20 (10 ng/g and 100 ng/g body weight (bw)), except GnRHR and fsh treated with 10 ng/gbw Pnx-20 in the pituitary and GnRHs in the hypothalamus. These results indicate that Pnx may not only stimulate the reproduction of the S. argus through the hypothalamic-pituitary-gonadal (HPG) axis, but also directly through the pituitary. Highlights • The hypothalamic expression of pnx in phase IV was significantly higher than in phase II and III during ovarian development. • pnx expression was highest in phase IV, moderate in phase III, and lowest in phase II in the female pituitary. • In vitro and in vivo Pnx treatments increase the expression levels of GnRHR , lh and fsh in the pituitary. [ABSTRACT FROM AUTHOR]

Abstract Phoenixin (Pnx) is an endogenous peptide known to be involved in reproduction and food intake in rats, with two active isoforms, phoenixin-14 (Pnx-14) and phoenixin-20 (Pnx-20). However, little is known about the functions of Pnx in teleost. Here, pnx was cloned and was detected in all tissues of both male and female in spotted scat (Scatophagus argus), including growth axis, hypothalamus, pituitary, and liver. Real-time PCR analysis showed that pnx in the hypothalamus increased significantly after 2 d and 7 d fasting, while reduced significantly after re-feeding (P < 0.05). When pituitary and liver fragments were cultured in vitro with Pnx-14 and Pnx-20 (10 nM and 100 nM) for 6 h, the expression of ghrhr (growth hormone-releasing hormone receptor) and gh (growth hormone) in the pituitary, and ghr1 (growth hormone receptor 1) in the liver increased significantly, except ghr2 (growth hormone receptor 2) incubated with 10 nM and 100 nM Pnx-20 and ghr1 incubated with 10 nM Pnx-20. Similarly, the expression of ghrhr and gh in the pituitary, as well as ghr1 and ghr2 in the liver, increased significantly after injecting S. argus with Pnx-14 and Pnx-20 (10 ng/g and 100 ng/g body weight). These results indicate that Pnx is likely to be involved in the regulation of food intake, and also regulates the growth of S. argus by increasing ghrhr and gh expression in the pituitary, ghr1 and ghr2 in the liver, and ghr1 directly in the liver. [ABSTRACT FROM AUTHOR]

To our knowledge, this is the first study to investigate the high-frequency (100–300 kHz) switching stability of SiC power devices at a Vds of 800 V during hard switching (HSW) and zero voltage switching (ZVS) operations. In this study, we proposed a topology for evaluating the switching dependencies (i.e., temperature, frequency, current, and duty cycle) in order to determine their flexibility in identifying circuit-level switching stability. We also evaluated the high-frequency switching stability of GaN power devices for comparison purposes. Overall, the results indicated that compared with GaN power devices, SiC power devices have higher dynamic drain-to-source on-resistance stability during ZVS and HSW high-frequency switching operations. • Investigate the high-frequency (100–300 kHz) switching stability of SiC power devices. • Propose a topology for evaluating the switching dependencies (i.e., temperature, frequency, current, and duty cycle). • Evaluate the high-frequency switching stability of GaN power devices for comparison purposes. • SiC power devices have higher dynamic drain-to-source on-resistance stability. [ABSTRACT FROM AUTHOR]

This paper investigates the robustness of normally-off High Electron Mobility Transistors (HEMTs) with p-GaN gate submitted to forward gate bias overstress. By means of combined DC and spectral analysis we demonstrate the following results: (i) the devices demonstrate a time-dependent failure mechanism; (ii) time to failure (TTF) can be described by a Weibull distribution with a shape factor higher than 1, suggesting a wear-out failure; (iii) the devices have an estimated 20-years lifetime for a gate voltage of 7.2 V; (iv) TTF is temperature-dependent, with an activation energy of 0.5 eV; (v) emission microscopy reveals the presence of hot spots, whose emission originates from yellow luminescence and/or hot electron radiation. [ABSTRACT FROM AUTHOR]

In this work, the relaxation analysis is performed to understand the V TH instability in FeFETs with two different dopants, i.e., Si and Gd. The FeFETs with different dopants show the different delay-after-write characteristics, i.e., Gd:HfO 2 FeFETs show a better delay-after-write stability compared to the case of Si:HfO 2 FeFETs. With the relaxation analysis, Si:HfO 2 FeFETs exhibit an obvious V TH recovery during the relaxation phases. Furthermore, the power law fitting is used to analyze the V TH shift under the positive program bias, indicating that a wide and easily accessible defects can exist in the IL and/or Si:HfO 2 since the smaller overdrive voltage dependence exponent (γ) is obtained in Si:HfO 2. Last, the smaller V TH shift/recovery in Gd:HfO 2 FeFETs can be attributed to a relatively tighter defect distribution, indicating that the dopants in the ferroelectric layer and the defects in IL and/or ferroelectric dielectric have to be carefully optimized to achieve the better V TH stability. • Si:HfO 2 FeFETs exhibit an obvious V TH recovery during the relaxation phases. • The power law fitting is used to analyze the V TH shift, indicating that a wide and easily accessible defects can exist in the IL and/or Si:HfO 2. • The smaller V TH shift/recovery in Gd:HfO 2 FeFETs indicates that the dopants and the defects have to be carefully optimized to achieve the better V TH stability. [ABSTRACT FROM AUTHOR]

This paper reports an extensive analysis of the trapping and reliability issues in AlGaN/GaN metal insulator semiconductor (MIS) high electron mobility transistors (HEMTs). The study was carried out on three sets of devices with different gate insulators, namely PEALD SiN, RTCVD SiN and ALD Al 2 O 3 . Based on combined dc, pulsed and transient measurements we demonstrate the following: (i) the material/deposition technique used for the gate dielectric can significantly influence the main dc parameters (threshold current, subthreshold slope, gate leakage) and the current collapse; and (ii) current collapse is mainly due to a threshold voltage shift, which is ascribed to the trapping of electrons at the gate insulator and/or at the AlGaN/insulator interface. The threshold voltage shift (induced by a given quiescent bias) is directly correlated to the leakage current injected from the gate; this demonstrates the importance of reducing gate leakage for improving the dynamic performance of the devices. (iii) Frequency-dependent capacitance–voltage (C–V) measurements demonstrate that optimized dielectric allow to lower the threshold-voltage hysteresis, the frequency dependent capacitance dispersion, and the conductive losses under forward-bias. (iv) The material/deposition technique has a significant impact on device robustness against gate positive bias stress. Time to failure is Weibull-distributed with a beta factor not significantly influenced by the properties of the gate insulator. The results presented within this paper provide an up-to-date overview of the main advantages and limitations of GaN-based MIS HEMTs for power applications, on the related characterization techniques and on the possible strategies for improving device performance and reliability. [ABSTRACT FROM AUTHOR]

Development of integration of different components with GaN-based technologies has been gaining traction in recently. Among these, diodes play important roles in GaN power ICs. For this work, a fabrication approach for integrating a Schottky barrier diode (SBD) with a p-GaN enhancement (E-mode) for 200 V switching application is demonstrated. The integrated SBD with 30-mm width shows a low forward voltage (V f) with more than 10A and 6A at V ac = 3 V at 25 °C and 150 °C, respectively. Additionally, the devices show a stable ON-resistance (R ON) (<20% increase) up to 200 V at 25 °C/150 °C under pulsed IV characterization and OFF-state stress, pointing out the robust stability for integrated GET-SBDs on a power p-GaN HEMT platform. [ABSTRACT FROM AUTHOR]

In this work, we have demonstrated the wireless power transfer (WPT) system based on the pristine and irradiated E-mode GaN devices. The GaN device has been irradiated up to the 100 kGy dose under the γ-ray irradiation, showing the improved electrical characteristic, such as the drain current increase (~8.34%) and gate current decrease (~−7.79%). An off-state drain induced instability measurement shows the robust performance in pristine and irradiated GaN device. Noted that the irradiated device exhibits less ΔV TH , suggesting the device instability has been improved. Moreover, the wireless power transfer efficiency was evaluated by utilizing different load (20 Ω ~ 120 Ω) at V DS = 50 V and V GS = 4 V. The results indicate that the transfer efficiency of WPT by implementing the pristine and irradiated GaN device are similar. Furthermore, the output power of WPT using the irradiated GaN device becomes higher, which is mainly due to the improved drain current in irradiated GaN power devices. • Demonstration of the wireless power transfer (WPT) system based on the pristine and irradiated E-mode GaN devices. • The GaN device has been irradiated (γ-ray with 100kGy dose), showing the I D increase (~8.34%) and I G decrease (~-7.79%). • The wireless power transfer efficiency was evaluated by utilizing different loads (20 Ω~120 Ω) at V DS = 50V and V GS = 4V. • The transfer efficiency of WPT by implementing pristine and irradiated GaN device are similar. • Furthermore, the output power of WPT using the irradiated GaN device becomes higher. [ABSTRACT FROM AUTHOR]

In this work, we observe the distinct V TH characteristics in the Au-free gate-first processing p-GaN/AlGaN/GaN HEMTs with two commonly used passivation layers, i.e., SiN and SiO 2. The lower incorporated H was found in the p-GaN/AlGaN/GaN heterostructure with higher activation anneal temperature (i.e., 700 °C). Furthermore, Photoluminescence (PL) spectrum demonstrates a higher blue luminescence (BL) intensity after higher annealing treatment. The X-ray photoelectron spectroscopy (XPS) spectrum near valence band edge depicts a similar valence band maximum (VBM) characteristic, by means no impact on p-GaN surface bending by using distinct thermal treatment. The device with SiN shows a depletion-mode (D-mode) characteristic (V TH ~ -5 V) whereas the device with SiO 2 passivation exhibits an enhancement-mode (E -mode) characteristic (V TH ~ +0.7 V). Moreover, Transmission Line Model (TLM) devices are fabricated to investigate the effects of the passivation on two-dimensional electron gas (2DEG) in p-GaN/AlGaN/GaN stack. The results indicate that a low R sh is obtained while passivating device surface with SiN layer, suggesting that 2DEG is present, which is most probably due to an unfunctional p-GaN layer. The secondary ion mass spectrometry (SIMS) results indicate a high hydrogen intensity in the p-GaN/AlGaN/GaN stack with a SiN passivation layer. Thus, the p-GaN deactivation process that correlates to the formation of complex Mg H after SiN passivation is proposed to explain the D-mode characteristic in the device with a SiN passivation layer. [ABSTRACT FROM AUTHOR]

In this work, GaN-on-Si power Metal-Insulator-Semiconductor High Electron Mobility Transistors (MIS-HEMTs) are irradiated through different regimes of cumulative γ -ray irradiation, namely 1, 2, 3, 4, and 5 kGy for the first sample; 1, 3, and 5 kGy for the second sample; 1, 5, and 10 kGy for the third sample; and 1, 10, and 20 kGy for the fourth sample. After each irradiation dose, drain current (I D), threshold voltage (V Th), and gate leakage current (I g) are electrically characterized in all the samples. An improvement in I D with a shift in V Th is observed in all the samples, which saturates after a higher irradiation dose. X-ray photoelectron spectroscopy (XPS) analysis confirms creation of nitrogen vacancies that act as donor and improves the I D. No significant change in I g is observed except for an increase in noise in gate leakage current. Scanning electron microscopy (SEM) shows the Al-based metallization pad degrades due to formation of small cavities. Finally, energy dispersive X-ray (EDX) analysis confirms the formation of Al native oxides due to γ -ray irradiation. [ABSTRACT FROM AUTHOR]