Using U-Net convolutional neural network to model pixel-based electrostatic potential distributions in GaN power MIS-HEMTs.

This study demonstrates a novel use of the U-Net convolutional neural network (CNN) for modeling pixel-based electrostatic potential distributions in GaN metal-insulator-semiconductor high-electron mobility transistors (MIS-HEMTs) with various gate and source field plate designs and drain voltages. The pixel-based images of the potential distribution are successfully modeled from the developed U-Net CNN with an error of less than 1% error relative to a TCAD simulated reference of a 500-V electrostatic potential distribution in the AlGaN/GaN interface. Furthermore, the modeling time of potential distributions by U-Net takes about 80 ms. Therefore, the U-Net CNN is a promising approach to efficiently model the pixel-based distributions characteristics in GaN power devices.

Comprehensive Investigation of Constant Voltage Stress Time-Dependent Breakdown and Cycle-to-Breakdown Reliability in Y-Doped and Si-Doped HfO2 Metal-Ferroelectric-Metal Memory.

In this study, we comprehensively investigate the constant voltage stress (CVS) time-dependent breakdown and cycle-to-breakdown while considering metal-ferroelectric-metal (MFM) memory, which has distinct domain sizes induced by different doping species, i.e., Yttrium (Y) (Sample A) and Silicon (Si) (Sample B). Firstly, Y-doped and Si-doped HfO2 MFM devices exhibit domain sizes of 5.64 nm and 12.47 nm, respectively. Secondly, Si-doped HfO2 MFM devices (Sample B) have better CVS time-dependent breakdown and cycle-to-breakdown stability than Y-doped HfO2 MFM devices (Sample A). Therefore, a larger domain size showing higher extrapolated voltage under CVS time-dependent breakdown and cycle-to-breakdown evaluations was observed, indicating that the domain size crucially impacts the stability of MFM memory.

Demonstration of MOCVD-grown Ga2O3 power MOSFETs on sapphire with in-situ Si-doped by tetraethyl orthosilicate (TEOS).

In this work, we demonstrated Ga2O3-based power MOSFETs grown on c-plane sapphire substrates using in-situ TEOS doping for the first time. The ß-Ga2O3:Si epitaxial layers were formed by the metalorganic chemical vapor deposition (MOCVD) with a TEOS as a dopant source. The depletion-mode Ga2O3 power MOSFETs are fabricated and characterized, showing the increase of the current, transconductance, and breakdown voltage at 150 °C. In addition, the sample with the TEOS flow rate of 20 sccm exhibited a breakdown voltage of more than 400 V at RT and 150 °C, indicating that the in-situ Si doping by TEOS in MOCVD is a promising method for Ga2O3 power MOSFETs.

Multiple-State Nonvolatile Memory Based on Ultrathin Indium Oxide Film via Liquid Metal Printing.

In this work, the ultrathin two-dimensional (2D) indium oxide (InOx) with a large area of more than 100 µm2 and a high degree of uniformity was automatically peeled off from indium by the liquid-metal printing technique. Raman and optical measurements revealed that 2D-InOx has a polycrystalline cubic structure. By altering the printing temperature which affects the crystallinity of 2D-InOx, the mechanism of the existence and disappearance of memristive characteristics was established. The tunable characteristics of the 2D-InOx memristor with reproducible one-order switching was manifest from the electrical measurements. Further adjustable multistate characteristics of the 2D-InOx memristor and its resistance switching mechanism were evaluated. A detailed examination of the memristive process demonstrated the Ca2+ mimic dynamic in 2D-InOx memristors as well as the fundamental principles underlying biological and artificial synapses. These surveys allow us to comprehend a 2D-InOx memristor using the liquid-metal printing technique and could be applied to future neuromorphic applications and in the field of revolutionary 2D material exploration.

Study on the Effects of Quantum Well Location on Optical Characteristics of AlGaN/GaN Light-Emitting HEMT.

In this study, AlGaN/GaN light-emitting HEMTs (LE-HEMT) with a single quantum well inserted in different locations in the epitaxy layers are fabricated and analyzed. For both structures, light-emitting originated from electrons in the 2DEG and holes from the p-GaN for radiative recombination is located in the quantum well. To investigate the importance of the location of single quantum well, optical characteristics are compared by simulation and experimental results. The experimental results show that the main light-emitting wavelength is shifted from 365 nm in the UV range to 525 nm in the visible range when the radiative recombination is confined in the quantum well and dominates among other mechanisms. Epi B, which has a quantum well above the AlGaN barrier layer in contrast to Epi A which has a quantum well underneath the barrier, shows better intensity and uniformity in light-emitting. According to the simulation results showing the radiative distribution and electron concentrations for both structures, the lower quantum efficiency is due to the diverse current paths in Epi A. On the other hand, Epi B shows better quantum confinement and therefore better luminescence in the same bias condition, which is consistent with experimental observations. These findings are critical for advancing the performance of LE-HEMTs.

GaN-based mini-LED matrix applied to multi-functional forward lighting.

In this paper, we propose and demonstrate to use of a single reflector with 68 segments to project vehicle low beam and high beam with the use of a GaN-based mini-LED matrix, which is a 5 × 6 LED die array. The design of the reflector is based on light field technology in considering etendue from the light source across the segments. The group of the segments with smaller etendue from the LED dies in the bottom 2 rows are used to project low beams. When the other LED dies are turned on, the reflector will project light upward and form the high beam. The selection of the turn-on LED dies in the mini-LED matrix can adjust the width of the illumination pattern so that an adaptive low/high beam can be performed. Besides, to extend the functionality of the headlamp module, we propose to dispense IR phosphor on LED dies in the high-beam zone of the GaN-based mini-LED matrix. Thus the vehicle can emit IR high beam, which can be imaged through a camera and can be incorporated with machine vision for an autonomous vehicle without using a complicated adaptive headlight to avoid glare. The proposed multi-function in spatial and spectral domains will be helpful to various applications with use of a mini-LED matrix.

Enhancement of Ferroelectricity in 5 nm Metal-Ferroelectric-Insulator Technologies by Using a Strained TiN Electrode.

In this work, the ferroelectric characteristic of a 5 nm Hf0.5Zr0.5O2 (HZO) metal-ferroelectric-insulator-semiconductor (MFIS) device is enhanced through strained complementary metal oxide semiconductor (CMOS)-compatible TiN electrode engineering. Strained TiN top-layer electrodes with different nitrogen (N) concentrations are deposited by adjusting the sputtering process conditions. The TiN electrode with 18% N exhibits a compressive characteristic, which induces tensile stress in a 5 nm HZO film. A device with 18% N in TiN shows a higher remanent polarization (2Pr) and larger capacitance value than the compared sample, indicating that the strained TiN is promising for enhancing the ferroelectricity of sub-5 nm HZO devices.

Investigation of Recessed Gate AlGaN/GaN MIS-HEMTs with Double AlGaN Barrier Designs toward an Enhancement-Mode Characteristic.

In this work, recessed gate AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) with double AlGaN barrier designs are fabricated and investigated. Two different recessed depths are designed, leading to a 5 nm and a 3 nm remaining bottom AlGaN barrier under the gate region, and two different Al% (15% and 20%) in the bottom AlGaN barriers are designed. First of all, a double hump trans-conductance (gm)-gate voltage (VG) characteristic is observed in a recessed gate AlGaN/GaN MIS-HEMT with a 5 nm remaining bottom Al0.2Ga0.8N barrier under the gate region. Secondly, a physical model is proposed to explain this double channel characteristic by means of a formation of a top channel below the gate dielectric under a positive VG. Finally, the impacts of Al% content (15% and 20%) in the bottom AlGaN barrier and 5 nm/3 nm remaining bottom AlGaN barriers under the gate region are studied in detail, indicating that lowering Al% content in the bottom can increase the threshold voltage (VTH) toward an enhancement-mode characteristic.

Estradiol-17ß regulates the expression of insulin-like growth factors 1 and 2 via estradiol receptors in spotted scat (Scatophagus argus).

Insulin-like growth factors (Igf1 and Igf2) play a key role in growth and development of vertebrates. In mammals, the expression of IGFs is regulated by estradiol-17ß (E2) via estrogen receptors (ESRs). The expression of igfs can also be regulated by E2 in fish, while comparative study of this is still lacking. The present study examined tissue distribution of igfs and hepatic expression of igfs and esrs during gonad development in Scatophagus argus by real-time PCR. Serum E2 concentration was measured by enzyme-linked immunosorbent assay (ELISA). The hepatic expression of igfs and esrs at gonadal phase III, incubated with either E2 (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 E2 concentration increased, while igf2 and esr2a expressions decreased, during ovary development. Igfs and esrs expressions increased while serum E2 concentration maintained low during testis development. In females, E2 incubation enhanced the expressions of igf1 and esr1 but inhibited that of igf2 and esr2a. Both fulvestrant and MPP inhibited up-regulation effect of E2 on igf1 and esr1. Fulvestrant enhanced down-regulation effect of E2 on igf2 and esr2a, but MPP conversely. In males, E2 incubation enhanced the expressions of igfs, esr1 and esr2a. Fulvestrant and MPP inhibited up-regulation effect of E2 on igfs and esr1. PHTPP inhibited igf1 and esr2 expressions in both sexes. Our results indicated that the expression of igfs is regulated by E2 via Esrs in S. argus.

Phoenixin: Expression at different ovarian development stages and effects on genes ralated to reproduction in spotted scat, Scatophagus argus.

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.

Phoenixin participated in regulation of food intake and growth in spotted scat, Scatophagus argus.

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.

Molecular cloning, characterization and expression analysis of spexin in spotted scat (Scatophagus argus).

Spexin (Spx), a novel neuropeptide, composed of 14 amino acid residues, is evolutionally conserved from fish to mammals. It has been suggested that Spx has pleiotropic functions in mammals. However, reports about Spx are very limited. To clarify the roles of Spx in the regulation of reproduction and food-intake in the spotted scat, the spx (ssspx) gene was cloned and analyzed. Analysis of the tissue distribution by RT-PCR showed that ssspx expression was widespread. During ovary development, expression of ssspx was found to be highest in phase II, moderate in phase III, and at its lowest level in phase IV. Ssspx expression was significantly down-regulated in the hypothalamus after treatment with E2 both in vitro and in vivo. A significant increase of ssspx was observed after 2 and 7 days of food deprivation. However, the ssspx transcript levels in the 7 day fasting group decreased significantly after refeeding 3 h after the scheduled feeding time. This suggests that ssSpx may be involved in the regulation of reproduction and food-intake in the spotted scat.

Cloning, expression and functional characterization on vitellogenesis of estrogen receptors in Scatophagus argus.

Estrogen receptors (Er) play a critical role in vitellogenesis. Three ers (erα, erß1 and erß2) and vitellogenins (vtg-A, vtg-B and vtg-C) subtypes were isolated in various fish species, while the contribution of each Er to the regulation of vtgs expression was not analyzed in detail. Here, erα, erß1 and erß2 were cloned and all were found to be expressed in female liver in Scatophagus argus. During proteic vitellogenesis stage, erα was simultaneously up-regulated, while erß1 and erß2 were not, with three vtgs in female liver. The effects of 17ß-estradiol (E2) alone or combined with Er antagonists on ers, vtgs mRNA expressions and Vtg protein content in incubated male liver were examined by real-time PCR and enzyme-linked immunosorbent assay (ELISA), respectively. The expressions of erα, erß1, vtgs mRNA and Vtg protein increased significantly after 24h incubation with E2 (0.1, 1 and 10µM), while Er nonselective antagonist ICI 182 780 (0.01, 0.1 and 1µM) significantly attenuated the up-regulation effects of E2 on ers, vtgs mRNA and Vtg protein in a dose-dependent manner. Erα selective antagonist Methyl-piperidinopyrazole (MPP) (0.01, 0.1 and 1µM) significantly attenuated the up-regulation effects of E2 on erα, vtg-B, vtg-C mRNA and Vtg protein, while promoted the expression of erß1 and vtg-A. Erß selective antagonist Cyclofenil (0.01, 0.1 and 1µM) attenuated the up-regulation effects of E2 on erß1, erß2, vtg-A, vtg-C mRNA and Vtg protein while promoted the expression of erα and vtg-B. Our results suggest that the regulation of Ers on different vtgs was divergent in S. argus.