Novel devices such as tunneling field-effect transistors (FETs) and ferroelectric FETs have been demonstrated to break the subthreshold swing (SS) limit with sub-60 mV/decade switching for further low voltage/low power applications. In this paper, SS of sub-60 mV/dec was firstly observed in InAlN/GaN high electron mobility transistors (HMETs): an average SS of 30 mV/dec over three orders of magnitude in drain-source (Ids) and a minimum point-by-point SS of 15 mV/dec were achieved in the InAlN/GaN HEMTs with gate length (Lg) of 40 nm. It is found that SS decreases with drain-source voltage (Vds) as well as Lg, and falls below 60 mV/dec when Lg < 100 nm. The decrease of SS as the device dimension scales down is attributed to the tunneling of high energy electrons from channel to the surface. The SS decreasing with the nanoscale gate length shows the great potential of the InAlN/GaN HEMTs to be applied in future logic switches.
A GaN resonant cavity light emitting diode was built on a GaN-AlN distributed Bragg reflector grown on a silicon substrate. The electroluminescence output increased by 2.5 times for a GaN diode coupled to a properly designed resonant cavity. Theoretical calculations showed that this enhancement could increase up to four times for transmission through a sem-transparent metal contact design, up to eight times for a flip-chip design
We demonstrate high-frequency (> 3 GHz), high quality factor radio frequency (RF) resonators in unreleased thin film gallium nitride (GaN) on sapphire and silicon carbide substrates by exploiting acoustic guided mode (Lamb wave) resonances. The associated energy trapping, due to mass loading from the gold electrodes, allows us to efficiently excite these resonances from a 50 $Ω$ input. The higher phase velocity, combined with lower electrode damping, enables high quality factors with moderate electrode pitch, and provides a viable route towards high-frequency piezoelectric devices. The GaN pla…
Achieving monolithic integration of passive acoustic wave devices, in particular RF filters, with active devices such as RF amplifiers and switches, is the optimal solution to meet the challenging communication requirements of mobile devices, especially as we move towards the 6G era. This requires a significant ($\approx$100x) reduction in the size of the RF passives, from mm$^2$ footprints in current devices to tens of $μm^2$ in future systems. Applying ideas from integrated photonics, we demonstrate that high frequency (>3 GHz) sound can be efficiently guided in $μ$m-scale gallium nitride(Ga…
A process for growing gallium nitride (GaN) vertical p-i-n homojunctions on (111) silicon (Si) substrates using metalorganic chemical vapor deposition (MOCVD) was developed, and a triple mesa etch technique was used to fabricate efficient betavoltaic energy converters. Monte Carlo simulation platform CASINO was used to model beta radiation penetration into GaN to aid device design. The resulting devices were tested under irradiation from a scanning electron microscope (SEM) electron beam (e-beam) tuned to imitate the energies of the 63Ni beta emission spectrum. Based on current-voltage (I-V) m…
We have presented an analytical physics-based compact model of GaN power FET, which can accurately describe the I-V characteristics in all operation modes. The model considers the source-drain resistance, different interface trap densities and self-heating effects.
We demonstrate post-fabrication target-wavelength trimming with a gallium phosphide on silicon nitride integrated photonic platform using controlled electron-beam exposure of hydrogen silsesquioxane cladding. A linear relationship between the electron-beam exposure dose and resonant wavelength red-shift enables deterministic, individual trimming of multiple devices on the same chip to within 30 pm of a single target wavelength. Second harmonic generation from telecom to near infrared at a target wavelength is shown in multiple devices with quality factors on the order of $10^4$. Post-fabricati…
Among the wide-bandgap compound semiconductors, gallium nitride is the most widely available material due to its prevalence in the solid state lighting and high-speed/high-power electronics industries. It is now known that GaN is one of only a handful of materials to host color centers that emit quantum light at room temperature. In this paper, we report on a bright color center in a semi-polar gallium nitride substrate, emitting at room temperature in the near-infrared. We show that a hemispherical solid immersion lens, near index matched to the semiconductor, can be used to enhance the photo…
A two-dimensional model was developed to simulate the optoelectronic characteristics of indium-gallium-nitride (InGaN), thin-film, Schottky-barrier solar cells. The solar cells comprise a window, designed to reduce the reflection of incident light, Schottky-barrier and ohmic front electrodes, an n-doped InGaN wafer, and a metallic periodically corrugated back-reflector (PCBR). The ratio of indium to gallium in the wafer varies periodically throughout the thickness of the absorbing layer of the solar cell. Thus, the resulting InGaN wafer's optical and electrical properties are made to vary peri…
Gallium nitride (GaN) as a wide-band gap material has been widely used in solid-state lighting. Thanks to its high nonlinearity and high refractive index contrast, GaN-on-insulator (GaNOI) is also a promising platform for nonlinear optical applications. Despite its intriguing optical proprieties, nonlinear applications of GaN have rarely been studied due to the relatively high optical loss of GaN waveguides (2 dB/cm). In this letter, we report GaNOI microresonator with intrinsic quality factor over 2 million, corresponding to an optical loss of 0.26 dB/cm. Parametric oscillation threshold powe…
Single-photon emitters in gallium nitride (GaN) are gaining interest as attractive quantum systems due to the well-established techniques for growth and nanofabrication of the host material, as well as its remarkable chemical stability and optoelectronic properties. We investigate the nature of such single-photon emitters in GaN with a systematic analysis of various samples produced under different growth conditions. We explore the effect that intrinsic structural defects (dislocations and stacking faults), doping and crystal orientation in GaN have on the formation of quantum emitters. We inv…
Within the subgap of amorphous oxide semiconductors like amorphous indium gallium zinc oxide (a-IGZO) are donor-like and acceptor-like states that control the operational physics of optically transparent thin-film transistors (TFTs). Hydrogen incorporation into the channel layer of a top-gate a-IGZO TFT exists as an electron donor that causes an observed negative shift in the drain current-gate voltage ($\mathrm{I_{D} - V_{G}}$) transfer curve turn-on voltage. Normally, hydrogen is thought to create shallow electronic states just below the conduction band mobility edge, with the donor ionizati…
To realize the full spectrum of advantages that the III-nitride materials system offers, the demonstration of p-channel III-nitride based devices is valuable. Authors report the first p-type field effect transistor (pFET) based on an AlGaN/GaN superlattice (SL), grown using MOCVD. Magnesium was used as the p-type dopant. A sheet resistance of 11.6 kΩ/sq, and a contact resistance of 14.9Ω.mm was determined using transmission line measurements (TLM) for a Mg doping of 1.5e19cm^-3 of Mg. Mobilities in the range of 7-10 cm\^2/Vs and a total sheet charge density in the range of 1e13-6e13 cm-2 were …
Ultraviolet microdisk lasers are integrated monolithically into photonic circuits using a III-nitride on silicon platform with gallium nitride (GaN) as the main waveguiding layer. The photonic circuits consist of a microdisk and a pulley waveguide terminated by out-coupling gratings. We measure quality factors up to 3500 under continuous-wave excitation. Lasing is observed from 374 nm to 399 nm under pulsed excitation, achieving low threshold energies of $0.14 ~\text{mJ/cm}^2$ per pulse (threshold peak powers of $35 ~\text{kW/cm}^2$). A large peak to background dynamic of around 200 is observe…
Nano-membrane tri-gate beta-gallium oxide (\b{eta}-Ga2O3) field-effect transistors (FETs) on SiO2/Si substrate fabricated via exfoliation have been demonstrated for the first time. By employing electron beam lithography, the minimum-sized features can be defined with a 50 nm fin structure. For high-quality interface between \b{eta}-Ga2O3 and gate dielectric, atomic layer-deposited 15-nm-thick aluminum oxide (Al2O3) was utilized with Tri-methyl-aluminum (TMA) self-cleaning surface treatment. The fabricated devices demonstrate extremely low subthreshold slope (SS) of 61 mV/dec, high drain curren…
Outstanding wide-bandgap semiconductor material such as gallium nitride (GaN) has been extensively utilized in power electronics, radiofrequency amplifiers, and harsh environment devices. Due to its quantum confinement effect in enabling desired deep-ultraviolet emission, excitonic impact, and electronic transport features, two-dimensional (2D) or ultrathin quasi-2D GaN semiconductors have been one of the most remarkable candidates for future growth of microelectronic devices. Here, for the first time, we reported a large area, wide bandgap, and room-temperature quasi-2D GaN synthesis and prin…
The quality of graphene in nanodevices has increased hugely thanks to the use of hexagonal boron nitride as a supporting layer. This paper studies to which extent hBN together with channel length scaling can be exploited in graphene field effect transistors (GFETs) to get a competitive radio frequency (RF) performance. Carrier mobility and saturation velocity were obtained from an ensemble Monte Carlo simulator that accounted for the relevant scattering mechanisms (intrinsic phonons, scattering with impurities and defects, etc.). This information is fed into a self consistent simulator, which …
In this letter, we report on the quantitative estimates of various metrics of performance for \b{eta}-Ga2O3 based High Electron Mobility Transistor (HEMT) for radio frequency (RF) and power applications and compare them with III-nitride devices. It is found that despite a lower cut-off frequency, \b{eta}- Ga2O3 HEMT is likely to provide higher RF output power compared to GaN-HEMT in the low-frequency regime although a poor thermal conductivity will impose limitations in heat dissipation. On the other hand, a much lower electron mobility will limit the DC switching performance in terms of effic…
We demonstrate ferroelectric (FE) memory transistors on a crystalline silicon channel with endurance exceeding $10^{10}$ cycles. The ferroelectric transistors (FeFETs) incorporate a high-$κ$ interfacial layer (IL) of thermally grown silicon nitride (SiN$_x$) and a thin 4.5 nm layer of Zr-doped FE-HfO$_2$ on a $\sim$30 nm SOI channel. The device shows a $\sim$ 1V memory window in a DC sweep of just $\pm$ 2.5V, and can be programmed and erased with voltage pulses of $V_G= \pm$ 3V at a pulse width of 250 ns. The device also shows very good retention behavior. These results indicate that appropria…
Effects of residual C impurities and Ga vacancies on the dynamic instabilities of AlN/AlGaN/GaN metal insulator semiconductor high electron mobility transistors are investigated. Secondary ion mass spectroscopy, positron annihilation spectroscopy, steady state and time-resolved photoluminescence (PL) measurements have been performed in conjunction with electrical characterization and current transient analyses. The correlation between yellow luminescence (YL), C- and Ga vacancy concentration is investigated. Time-resolved PL indicating the C$_{\mathrm{N}}$O$_{\mathrm{N}}$ complex as the main s…
The chemical activity of ionized hydrogen describes the potency of protons in solution and is used to define the pH with wide-ranging applications in biological and materials sciences. Measuring pH with graphene field-effect transistors (FETs) has been described in the past but has yet to be characterized with a monolayer hexagonal boron nitride (hBN) capping layer. hBN capping is hypothesized to lower the chemical affinity of protons to oxidized defects in the graphene crystal and lower the standard deviation of pH measurement via screening charge density. First, the electronic properties of …
We report the first observation of ferroelectric gating in AlScN barrier wide-bandgap nitride transistors. These FerroHEMT devices realized by direct epitaxial growth represent a new class of ferroelectric transistors in which the semiconductor is itself polar, and the crystalline ferroelectric barrier is lattice-matched to the substrate. The FerroHEMTs reported here use the thinnest nitride high K and ferroelectric barriers to date to deliver the highest on currents at 4 A/mm, and highest speed AlScN transistors with fmax larger than 150 GHz observed in any ferroelectric transistor. The Ferro…
In 1963, Moll and Tarui suggested that the field-effect conductance of a semiconductor could be controlled by the remanent polarization of a ferroelectric (FE) material to create a ferroelectric field-effect transistor (FE-FET). However, subsequent efforts to produce a practical, compact FE-FET have been plagued by low retention and incompatibility with Complementary Metal Oxide Semiconductor (CMOS) process integration. These difficulties led to the development of trapped-charge based memory devices (also called floating gate or flash memory), and these are now the mainstream non-volatile memo…
Gallium nitride (GaN), as a promising alternative semiconductor to silicon, is of well-established use in photoelectronic and electronic technology. However, the vulnerable GaN surface has been a critical restriction that hinders the development of GaN-based devices, especially regarding device stability and reliability. Here, we overcome this challenge by converting the GaN surface into a gallium oxynitride (GaON) epitaxial nanolayer through an in-situ two-step "oxidation-reconfiguration" process. The oxygen plasma treatment overcomes the chemical inertness of the GaN surface, and the sequent…
We present a method to obtain quantitative profiles of surface state charge density and monitor its dynamics under various stress conditions in high electron mobility transistor (HEMT) devices. The method employs an optical spectroscopy of the channel current at various bias conditions. We test the method on a classical AlGaN/GaN HEMT structure. To analyze the results, we propose a model, according to which the energy distribution of the surface charge density may be obtained from the derivative of the channel photocurrent. The proposed method is applied to fully fabricated transistors and can…
The emerging wide bandgap BAlN alloys have potentials for improved III-nitride power devices including high electron mobility transistor (HEMT). Yet few relevant studies have been carried. In this work, we have investigated the use of the B0.14Al0.86N alloy as part or entirety of the interlayer between the GaN buffer and the AlGaN barrier in the conventional GaN-based high electron mobility transistor (HEMT). The numerical results show considerable improvement of the two-dimensional electron gas (2DEG) concentration with small 2DEG leakage into the ternary layer by replacing the conventional A…
III-V heterostructure based high electron mobility transistors (HEMTs) offer superior performance as compared to CMOS silicon transistors owing to the high mobility in the 2D electron gas (2DEG) channel at the heterostructure interface. Gallium nitride (GaN) based HEMTs are also suitable for high power and high temperature applications. GaN has a rich offering of material properties spanning domains of nonlinear optics, piezoelectric micro-electro-mechanical systems (MEMS), and monolithic microwave integrated circuits (MMICs). In this paper, we propose HEMT inspired III-V electro-optic modulat…
An undoped AlGaN/GaN nanowire demonstrated p-type conductivity based solely on the formation of hole carriers in response to the negative polarization field at the (000-1) AlGaN/GaN facet. A transistor based on this nanowire displayed a low-voltage transition from Ohmic to space charge limited conduction. A numerical simulation showed that a highly asymmetric strain exists across the triangular cross-section, which creates a doublet peak in the piezoelectric induced polarization sheet charge at the (000-1) facet. Additionally, there is a strong interplay between the charge at the (000-1) AlGaN…
Localized residual stress and elastic strain concentrations in microelectronic devices often affect the electronic performance, resistance to thermomechanical damage, and, likely, radiation tolerance. A primary challenge for characterization of these concentrations is that they exist over sub-$μ$m length-scales, precluding their characterization by more traditional residual stress measurement techniques. Here we demonstrate the use of synchrotron X-ray -based differential aperture X-ray microscopy (DAXM) as a viable, non-destructive means to characterize these stress and strain concentrations …
Solid-state quantum emitters (QEs) are fundamental in photonic-based quantum information processing. There is strong interest to develop high-quality QEs in III-nitride semiconductors because of their sophisticated manufacturing driven by large and growing applications in optoelectronics, high voltage power transistors, and microwave amplifiers. Here, we report the generation and direct integration of QEs in an aluminium nitride-based photonic integrated circuit platform. For individual waveguide-integrated QEs, we measure an off-chip count rate exceeding $6 \times 10^{4}$ counts per second (c…
Diamond heat-spreaders for gallium nitride (GaN) devices currently depend upon a robust wafer bonding process. Bonding-free membrane methods demonstrate potential, however, chemical vapour deposition (CVD) of diamond directly onto a III-nitride (III-N) heterostructure membrane induces significant thermal stresses. In this work, these thermal stresses are investigated using an analytical approach, a numerical model and experimental validation. The thermal stresses are caused by the mismatch in the coefficient of thermal expansion (CTE) between the GaN/III-N stack, silicon (Si) and the diamond f…
High throughput experimental methods are known to accelerate the rate of research, development, and deployment of electronic materials. For example, thin films with lateral gradients in composition, thickness, or other parameters have been used alongside spatially-resolved characterization to assess how various physical factors affect material properties under varying measurement conditions. Similarly, multi-layer electronic devices that contain such graded thin films as one or more of their layers can also be characterized spatially in order to optimize the performance. In this work, we apply…
Two-dimensional (2D) semiconductors are promising material candidates for next-generation nanoelectronics. However, there are fundamental challenges related to their metal-semiconductor (MS) contacts which limit the performance potential for practical device applications. In this work, we exploit 2D monolayer hexagonal boron nitride (h-BN) as an ultrathin decorating layer to form a metal-insulator-semiconductor (MIS) contact, and demonstrate a novel diode-like selective enhancement of the carrier transport through it. Compared to the conventional MS contact, the MIS contact dominated by both t…
Unlike the electrical conductance that can be widely modulated within the same material even in deep nanoscale devices, tuning the thermal conductance within a single material system or nanostructure is extremely challenging and requires a large-scale device. This prohibits the realization of robust ON/OFF states in switching the flow of thermal currents. Here, we present the theory of a thermal switch based on resonant coupling of three photonic resonators, in analogy to the field-effect electronic transistor composed of a source, gate, and drain. As a material platform, we capitalize on the …
