The electrical characteristics of a 4H-silicon carbide metal-insulator-semiconductor structure with Al_2O_3 as the gate dielectric

A 4H-silicon carbide metal-insulator-semiconductor structure with ultra-thin Al2O3 as the gate dielectric, deposited by atomic layer deposition on tile epitaxial layer of a 4H-SiC （0001） 80N-/N＋ substrate, has been fabricated. The experimental results indicate that the prepared ultra-thin Al2O3 gate dielectric exhibits good physical and electrical characteristics, including a high breakdown electrical field of 25 MV/cm, excellent interface properties （1 × 10^14 cm^-2） and low gate-leakage current （IG = 1 × 10^-3 A/cm 2@Eox = 8 MV/cm）. Analysis of the current conduction mecha- nism on the deposited Al2O3 gate dielectric was also systematically performed. The confirmed conduction mechanisms consisted of Fowler-Nordheim （FN） tuaneling, the Frenkel-Poole mechanism, direct tunneling and Schottky emission, and the dominant current conduction mechanism depends on the applied electrical field. When the gate leakage current mechanism is dominated by FN tunneling, the barrier height of SiC/Al2O3 is 1.4 eV, which can meet the requirements of silicon carbide metal-insulator-semiconductor transistor devices.

Photoresponse of the In0.3Ga0.7N metal-insulator-semiconductor photodetectors

In0.3Ga0.7N metal-insulator-semiconductor （MIS） and metal-semiconductor （MS） surface barrier photodetectors have been fabricated. The In0.3Ga0.7N epilayers were grown on sapphire by metalorganic chemical vapour deposition （MOCVD）. The photoresponse and reverse current-voltage characteristics of the In0.3Ga0.7N MIS and MS photodetectors were measured. A best zero bias responsivity of 0.18 A/W at 450 nm is obtained for the In0.3Ga0.7N MIS photodetector with 10 nm Si3N4 insulator layer, which is more than ten times higher than the In0.3Ga0.7N MS photodetector. The reason is attributed to the decrease of the interface states and increase of surface barrier height by the inserted insulator. The influence of the thickness of the Si3N4 insulator layer on the photoresponsivity of the MIS photodetector is also discussed.

Robust Performance of AlGaN-Channel Metal-Insulator-Semiconductor High-Electron-Mobility Transistors at High Temperatures

Superior characteristics of Al Ga N-channel metal-insulator-semiconductor（MIS） high electron mobility transistors（HEMTs） at high temperatures are demonstrated in detail. The temperature coefficient of the maximum saturation drain current for the Al GaN-channel MIS HEMT can be reduced by 50% compared with the Ga N-channel HEMT. Moreover, benefiting from the better suppression of gate current and reduced leakage current in the buffer layer, the Al Ga N-channel MIS HEMT demonstrates an average breakdown electric field of 1.83 MV/cm at25℃ and 1.06 MV/cm at 300℃, which is almost 2 times and 3 times respectively larger than that of the reference Ga N-channel HEMT. Pulsed mode analyses suggest that the proposed device suffers from smaller current collapse when the temperature reaches as high as 300℃.

C-V characteristics of piezotronic metal-insulator-semiconductor transistor

Third generation semiconductors for piezotronics and piezo-phototronics,such as Zn O and Ga N,have both piezoelectric and semiconducting properties.Piezotronic devices normally exhibit high strain sensitivity because strain-induced piezoelectric charges control or tune the carrier transport at junctions,contacts and interfaces.The distribution width of piezoelectric charges in a junction is one of important parameters.Capacitance-voltage(C-V)characteristics can be used to estimate the distribution width of strain-induced piezoelectric charges.Piezotronic metal–insulator-semiconductor(MIS)has been modelled by analytical solutions and numerical simulations in this paper,which can serve as guidance for C-V measurements and experimental designs of piezotronic devices.

Normally-off AlGaN/GaN heterojunction field-effect transistors with in-situ AlN gate insulator

AlGaN/GaN heterojunction field-effect transistors(HFETs)with p-GaN cap layer are developed for normally-off operation,in which an in-situ grown AlN layer is utilized as the gate insulator.Compared with the SiNxgate insulator,the AlN/p-GaN interface presents a more obvious energy band bending and a wider depletion region,which helps to positively shift the threshold voltage.In addition,the relatively large conduction band offset of AlN/p-GaN is beneficial to suppress the gate leakage current and enhance the gate breakdown voltage.Owing to the introduction of AlN layer,normally-off p-GaN capped AlGaN/GaN HFET with a threshold voltage of 4 V and a gate swing of 13 V is realized.Furthermore,the field-effect mobility is approximately 1500 cm^(2)·V^(-1)·s^(-1)in the 2DEG channel,implying a good device performance.

Temperature-dependent dielectric properties of Au/Si_3N_4/n-Si (metal insulator semiconductor) structures

The dielectric properties of Au/Si3N4/n-Si （MIS） structures are studied using the admittance measurements （C–V and G/ω–V） each as a function of temperature in a range from 80 K to 400 K for two frequencies （100 kHz and 1 MHz）. Experimental results show that both the dielectric constant （ε’） and the dielectric loss （ε＂） increase with temperature increasing and decrease with frequency increasing. The measurements also show that the ac conductivity （σac） increases with temperature and frequency increasing. The lnσac versus 1000/T plot shows two linear regions with different slopes which correspond to low （120 K–240 K） and high （280 K–400 K） temperature ranges for the two frequencies. It is found that activation energy increases with frequency and temperature increasing.

C-V Characterization of α-Fe_2O_3/Block-Copolymer Composite Particulate Films

α-Fe_2O_3 nanocrystal was encapsulated by a block-copolymer, hydroxylated poly (styrene-b- butadiene-styrene) (HO-SBS) to fabricate composite microspheres with α-Fe_2O_3 cores and HOSBS shell. Its film fabricated on n-Si wafer acts as the insulator layer in the metal-insulator- semiconductor(MIS) structure. The capacitance-voltage (C-V) properties were measured to characterize the composite particulate films.

The Influence of Different Type Irradiations on the Surface States Parameters of Si-SiO₂Structures

The results of experimental research of some effects in metal-insulator-semiconductor (MIS) structures induced by different types of radiation (50 MeV electrons, 12 keV gamma-quanta, 10 and 40 keV arsenic ions) are presented. It is found that there is a significant difference between the characters of radiation surface states (SS) formed by ionization and impact actions of the MIS structure irradiation at the insulator-semiconductor (I-S) interface. It is shown that the SS generation rate is increased in electric fields and depends on the MIS structure field electrode material.

Recent Advancements in Photoelectrochemical Water Splitting for Hydrogen Production

Sunlight is the most abundant and inexhaustible energy source on earth.However,its low energy density,dispersibility and intermittent nature make its direct utilization with industrial relevance challenging,suggesting that converting sunlight into chemical energy and storing it is a valuable measure to achieve global sustainable development.Carbon–neutral,clean and secondary pollution-free solar-driven water splitting to produce hydrogen is one of the most attractive avenues among all the current options and is expected to realize the transformation from dependence on fossil fuels to zero-pollution hydrogen.Artificial photosynthetic systems(APSs)based on photoelectrochemical(PEC)devices appear to be an ideal avenue to efficiently achieve solar-to-hydrogen conversion.In this review,we comprehensively highlight the recent developments in photocathodes,including architectures,semiconductor photoabsorbers and performance optimization strategies.In particular,frontier research cases of organic semiconductors,dye sensitization and surface grafted molecular catalysts applied to APSs based on frontier(molecular)orbital theory and semiconductor energy band theory are discussed.Moreover,research advances in typical photoelectrodes with the metal–insulator–semiconductor(MIS)architecture based on quantum tunnelling are also introduced.Finally,we discuss the benchmarks and protocols for designing integrated tandem photoelectrodes and PEC systems that conform to the solar spectrum to achieve high-efficiency and cost-effective solar-to-hydrogen conversion at an industrial scale in the near future.

Thin-barrier enhancement-mode AlGaN/GaN MIS-HEMT using ALD Al_2O_3 as gate insulator

A high-performance enhancement-mode （E-mode） gallium nitride （GaN）-based metal-insulator- semiconductor high electron mobility transistor （MIS-HEMT） that employs a 5-nm-thick aluminum gallium nitride （Al0.3Ga0.7N） as a barrier layer and relies on silicon nitride （SIN） passivation to control the 2DEG density is presented. Unlike the SiN passivation, aluminum oxide （AL2O3） by atomic layer deposition （ALD） on A1GaN surface would not increase the 2DEG density in the heterointerface. ALD AL2O3 was used as gate insulator after the depletion by etching of the SiN in the gate region. The E-mode MIS-HEMT with gate length （LG） of 1 μm showed a maximum drain current density （IDs） of 657 mA/mm, a maximum extrinsic transconductance （gin） of 187 mS/ram and a threshold voltage （Vth） of 1 V. Comparing with the corresponding E-mode HEMT, the device performances had been greatly improved due to the insertion of AL2O3 gate insulator. This provided an excellent way to realize E-mode A1GaN/GaN MIS-HEMTs with both high Vth and IDS.