III-V semiconductors have high mobility and will be used in field effect transistors with the appropriate gate dielectric. The dielectrics must have band offsets over 1eV to inhibit leakage. The band offsets of various gate dielectrics including HfO2, Al2O3, Gd2O3, Si3N4, and SiO2 on III-V semiconductors such as GaAs, InAs, GaSb, and GaN have been calculated using the method of charge neutrality levels. Generally, the conduction band offsets are found to be over 1eV, so they should inhibit leakage for these dielectrics. On the other hand, SrTiO3 has minimal conduction band offset. The valence band offsets are also reasonably large, except for Si nitride on GaN and Sc2O3 on GaN which are 0.6–0.8eV. There is reasonable agreement with experiment where it exists, although the GaAs:SrTiO3 case is even worse in experiment.

https://www.researchgate.net/file.PostFileLoader.html?id=53ba3e1fd2fd64bc5d8b4653&assetKey=AS%3A273553407053824%401442231622645

Band offsets of high K gate oxides on III-V semiconductors

Recent advances in flexible and stretchable electronics (FSE), a technology diverging from the conventional rigid silicon technology, have stimulated fundamental scientific and technological research efforts. FSE aims at enabling disruptive applications such as flexible displays, wearable sensors, printed RFID tags on packaging, electronics on skin/organs, and Internet-of-things as well as possibly reducing the cost of electronic device fabrication. Thus, the key materials components of electronics, the semiconductor, the dielectric, and the conductor as well as the passive (substrate, planarization, passivation, and encapsulation layers) must exhibit electrical performance and mechanical properties compatible with FSE components and products. In this review, we summarize and analyze recent advances in materials concepts as well as in thin-film fabrication techniques for high-k (or high-capacitance) gate dielectrics when integrated with FSE-compatible semiconductors such as organics, metal oxides, quantum...

High- k Gate Dielectrics for Emerging Flexible and Stretchable Electronics

High-performance metal-oxide-semiconductor field effect transistors (MOSFETs) on III–V semiconductors have long proven elusive. High-permittivity (high-κ) gate dielectrics may enable their fabrication. We have studied hafnium oxide and aluminum oxide grown on gallium arsenide by atomic layer deposition. As-deposited films are continuous and predominantly amorphous. A native oxide remains intact underneath HfO2 during growth, while thinning occurs during Al2O3 deposition. Hydrofluoric acid etching prior to growth minimizes the final interlayer thickness. Thermal treatments at ∼600°C decompose arsenic oxides and remove interfacial oxygen. These observations explain the improved electrical quality and increased gate stack capacitance after thermal treatments.

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HfO2 and Al2O3 gate dielectrics on GaAs grown by atomic layer deposition

Atomic-layer deposition (ALD) provides a unique opportunity to integrate high-quality gate dielectrics on III-V compound semiconductors. We report detailed leakage current and breakdown electric-field characteristics of ultrathin Al2O3 dielectrics on GaAs grown by ALD. The leakage current in ultrathin Al2O3 on GaAs is comparable to or even lower than that of state-of-the-art SiO2 on Si, not counting the high-k dielectric properties for Al2O3. A Fowler-Nordheim tunneling analysis on the GaAs∕Al2O3 barrier height is also presented. The breakdown electric field of Al2O3 is measured as high as 10MV∕cm as a bulk property. A significant enhancement on breakdown electric field up to 30MV∕cm is observed as the film thickness approaches to 1nm.

Leakage current and breakdown electric-field studies on ultrathin atomic-layer-deposited Al2O3 on GaAs

GalliumNitridebasedhighelectronmobilitytransistors(HEMTs)areattractiveforuseinhighpowerandhighfrequencyapplications, with higher breakdown voltages and two dimensional electron gas (2DEG) density compared to their GaAs counterparts. Specific applications for nitride HEMTs include air, land and satellite based communications and phased array radar. Highly efficient GaNbased blue light emitting diodes (LEDs) employ AlGaN and InGaN alloys with different compositions integrated into heterojunctions and quantum wells. The realization of these blue LEDs has led to white light sources, in which a blue LED is used to excite a phosphor material; light is then emitted in the yellow spectral range, which, combined with the blue light, appears as white. Alternatively, multiple LEDs of red, green and blue can be used together. Both of these technologies are used in high-efficiency white electroluminescent light sources. These light sources are efficient and long-lived and are therefore replacing incandescent and fluorescent lamps for general lighting purposes. Since lighting represents 20‐30% of electrical energy consumption, and because GaN white light LEDs require ten times less energy than ordinary light bulbs, the use of efficient blue LEDs leads to significant energy savings. GaN-based devices are more radiation hard than their Si and GaAs counterparts due to the high bond strength in III-nitride materials. The response of GaN to radiation damage is a function of radiation type, dose and energy, as well as the carrier density, impurity content and dislocation density in the GaN. The latter can act as sinks for created defects and parameters such as the carrier removal rate due to trapping of carriers into radiation-induced defects depends on the crystal growth method used to grow the GaN layers. The growth method has a clear effect on radiation response beyond the carrier type and radiation source. We review data on the radiation resistance of AlGaN/GaN and InAlN/GaN HEMTs and GaN‐based LEDs to different types of ionizing radiation, and discuss ion stopping mechanisms. The primary energy levels introduced by different forms of radiation, carrier removal rates and role of existing defects in GaN are discussed. The carrier removal rates are a function of initial carrier concentration and dose but not of dose rate or hydrogen concentration in the nitride material grown by Metal Organic Chemical Vapor Deposition. Proton and electron irradiation damage in HEMTs creates positive threshold voltage shifts due to a decrease in the two dimensional electron gas concentration resulting from electron trapping at defect sites, as well as a decrease in carrier mobility and degradation of drain current and transconductance. State-of-art simulators now provide accurate predictions for the observed changes in radiation-damaged HEMT performance. Neutron irradiation creates more extended damage regions and at high doses leads to Fermi level pinning while 60 Co γ-ray irradiation leads to much smaller changes in HEMT drain current relative to the other forms of radiation. In InGaN/GaN blue LEDs irradiated with protons at fluences near 10 14 cm −2 or electrons at fluences near 10 16 cm −2 , both current-voltage and light output-current characteristics are degraded with increasing proton dose. The optical performance of the LEDs is more sensitive to the proton or electron irradiation than that of the corresponding electrical performances. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any

https://iopscience.iop.org/article/10.1149/2.0251602jss/pdf

Review—Ionizing Radiation Damage Effects on GaN Devices

We report on a GaN metal-oxide-semiconductor high-electron-mobility-transistor (MOS-HEMT) using atomic-layer-deposited (ALD) Al2O3 as the gate dielectric. Compared to a conventional GaN high-electron-mobility-transistor (HEMT) of similar design, the MOS-HEMT exhibits several orders of magnitude lower gate leakage and several times higher breakdown voltage and channel current. This implies that the ALD Al2O3∕AlGaN interface is of high quality and the ALD Al2O3∕AlGaN∕GaN MOS-HEMT is of high potential for high-power rf applications. In addition, the high-quality ALD Al2O3 gate dielectric allows the effective two-dimensional (2D) electron mobility at the AlGaN∕GaN heterojunction to be measured under a high transverse field. The resulting effective 2D electron mobility is much higher than that typical of Si, GaAs or InGaAs metal-oxide-semiconductor field-effect-transistors (MOSFETs).

GaN metal-oxide-semiconductor high-electron-mobility-transistor with atomic layer deposited Al2O3 as gate dielectric

We report on a GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) using atomic layer deposition (ALD) Al2O3 film as a gate dielectric and for surface passivation simultaneously. Compared to the conventional AlGaN/GaN HEMT of the same design, six order of magnitude smaller gate leakage current and tripled drain current at forward gate bias demonstrate the effectiveness of ALD Al2O3 as a gate dielectric. The high transconductance and high effective two-dimensional electron mobility verify the high-quality of Al2O3/AlGaN interface with low interface trap density. The Al2O3 passivation effect is also studied by sheet resistance measurement and short pulse drain characterization.

S. Halder

Papers

GaN metal-oxide-semiconductor high-electron-mobility-transistor with atomic layer deposited Al2O3 as gate dielectric

GaN MOS-HEMT USING ATOMIC LAYER DEPOSITION Al2O3 AS GATE DIELECTRIC AND SURFACE PASSIVATION

GaN MOS-HEMT USING ATOMIC LAYER DEPOSITION Al2O3 AS GATE DIELECTRIC AND SURFACE PASSIVATION