In this work, we report on a GaN/AlGaN superlattice based normally-off hole channel FinFET devices. A combination of Schottky gate and 60 nm wide fins led to enhancement mode operation. The device had an on-current of 13 mA/mm and an on-resistance of $300~\Omega $ .mm. simultaneously, a large Ion/Ioff > 107 and a current modulation of more than two orders of magnitude in the enhancement mode regime was also achieved.

The shortcomings with acceptors in p-type III-nitride semiconductors have resulted in not many efforts being presented on III-nitride based p-channel electronic devices (here, field effect transistors (FETs)). The polarization effects in III-nitride superlattices (SLs) lead to the periodic oscillation of the energy bands, exhibiting enhanced ionization of the deep acceptors (Mg in this study), and hence their use in III-nitride semiconductor-based light-emitting diodes (LEDs) and p-channel FETs is beneficial. This study experimentally demonstrates the presence of acceptor-like traps at the positive polarization interfaces acting as the primary source of holes in Ga-polar p-type uniformly doped (AlGaN/AlN)/GaN SLs with limited Mg doping. The observed concentration of holes exceeding that of the dopants incorporated into the samples during growth can be attributed to the ionization of acceptor-like traps, located at 0.8 eV above the valence band of GaN, at positive polarization interfaces. All samples were grown using the metal organic vapor phase epitaxy (MOVPE) technique, and the materials’ characterization was carried out using X-ray diffraction and Hall effect measurements. The hole concentrations experimentally measured are juxtaposed with the calculated value of hole concentrations from FETIS®, and the measured trends in mobility are explained using the amplitude of separation of the two-dimensional hole gas in the systems from the positive polarization interfaces.

This study experimentally shows the existence of acceptor traps at positive polarization interfaces (PPIs) acting as the source of holes in N-polar p-type modulation doped GaN/(AlN/AlGaN) superlattices (SLs) with low Mg doping. The observation of measured hole concentration higher than the dopants (here, Mg) put in the samples during growth can be explained by the ionization of acceptor traps, which are placed 0.8 eV above the valence band of GaN at the PPI. All samples were epitaxially grown using metal organic chemical vapor deposition and were characterized using x-ray diffraction and room-temperature Hall measurements. The measured hole concentrations are compared against calculated values from STR FETIS®, and the measured mobility trends are explained using the separation of the positive polarization interfaces from the two-dimensional hole gas in the systems, strengthening the hypothesis. A second study is also presented where acceptor traps were ionized in a p-type modulation doped GaN/AlGaN SL without an AlN layer—by keeping the superlattice period thickness constant and increasing the AlGaN composition. Following the hypothesis of the existence of an acceptor trap, these experimental studies demonstrate the charge-balance in systems that show p-type behavior without sufficient doping.

There is a strong need for a large band gap pFET device with good performance for an efficient high voltage CMOS platform for power conversion applications. In this work, we report on GaN/ AlGaN superlattice based MES-FinFET devices with MOCVD regrown p+ contacts around the fins. 75 nm wide FinFETs showed a normally-off operation with an on-current of 65 mA/mm, highest ever reported for any GaN based E-mode pFETs. Simultaneously, a large I on /I off > 10 7 was also achieved.

To further increase the operation frequency of GaN high electron mobility transistors (HEMTs) with high power gain in the mm-wave band (30-300 GHz), channel thickness must be scaled. High-k dielectrics such as HfO2 can be inserted as gate insulator to reduce the leakage, while maintaining good gate control. In this work, we investigated HfO2 on N-polar HEMT structure by performing frequency dependent capacitance-voltage measurements on metal-oxide-semiconductor capacitors (MOSCAPs). The impact of annealing on the quality of HfO2 was studied. Moreover, we compared the CV characteristics of MOSCAPs with HfO2 deposited on the GaN channel with that deposited on the AlGaN cap layer. We showed that HfO2 deposition on AlGaN cap leads to Fermi level pinning, which prevents the channel being pinched off by applying gate voltage. On the other hand, well-behaved CV profiles were achieved by depositing HfO2 directly on GaN or SiN dielectric.

Hillock-free thick InGaN layers were grown on N-polar GaN on sapphire by metal organic vapor phase epitaxy using a digital growth scheme and H2 as surfactant. Introducing Mg to act as an additional surfactant and optimizing the H2 pulse time, In compositions up to 17% were obtained in 100 nm thick epilayers. Although Mg adversely affected the In incorporation, it enabled maintenance of a good surface morphology while decreasing the InGaN growth temperature, resulting in a net increase in In composition. The parameter space of growth temperature and Mg precursor flow to obtain hillock-free epilayers was mapped out.

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We propose the existence of an acceptor-like trap at positive polarization interfaces in p-type III-nitride semiconductor heterostructures, using N-polar p-type GaN/AlN/AlGaN superlattices as a demonstration platform. Metal Organic Vapor Phase Epitaxy was used to grow all samples, with a p-type modulation doping scheme using Mg as the dopant. The samples were characterized using x-ray diffraction and room-temperature Hall measurements, and energy band-diagram simulations were carried out using STR FETIS® and Silvaco packages. For higher doped samples (Mg > 1.5 × 1019 cm−3) with thinner AlN interlayers (≤0.7 nm), the total sheet charge measured using Hall measurements agreed with the value observed in standard simulations without invoking any traps, whereas for lower doped samples (Mg < 1.5 × 1019 cm−3) and those with thicker AlN interlayers (≥ 0.7 nm), the measured charge was very high compared to the value obtained from simulations and higher than the Mg doping in the films. The higher charge was attributed to the existence of an acceptor trap at positive polarization interfaces, which became ionized at lower doping and/or at higher AlN thicknesses. A consistent ionization energy of the trap was obtained by comparing the energy band diagram with and without acceptor traps with the experimental results. This work also elucidates the source of charge balance in p-type samples with insufficient or no Mg doping.

The properties of aluminum-silicon-oxide (AlSiO) dielectric with varying silicon composition, grown on (000-1) N-polar GaN, were investigated in this paper. The refractive index, dielectric constant, and film density of AlSiO decreased with the increase of the silicon composition as indicated by ellipsometry, low-frequency capacitance-voltage (CV), and x-ray reflectivity (XRR) measurements, respectively. Negligible frequency dispersion in CV measurements and high-intensity XRR oscillations peaks were measured for all AlSiO samples with different silicon compositions, suggesting a high-quality N-polar GaN-AlSiO interface. The leakage current characteristics and flat-band voltage stability improved with the increase of the silicon composition from 20% to 46% and degraded for the sample that had a silicon composition of 73%. This study contributes to understanding the AlSiO dielectric performance for future use in the gate stack of N-polar GaN-based transistors.

N-polar GaN MISHEMTs have recently demonstrated excellent power performance and power-added efficiency at 94 GHz [1] . At mm-wave frequencies and high data rates, the linearity of an RF transistor is an important requisite. Third-order non-linearities lead to undesirable effects such as in-band signal distortion and are therefore important to control. This study presents a novel device concept to enhance the linearity of N-polar GaN MISHEMTs at millimeter wave frequencies (30 GHz and beyond) for low-power receiver application. We have recently reported linearity data on N-polar GaN MISHEMTs with OIP3/P DC of 11.4 dB [2] and 15 dB [3] at 30 GHz. We have observed in [2] , [3] that the peak linearity performance is limited to a narrow input-bias range, resulting in susceptibility to process and temperature variations. Therefore, we explore a novel device structure that can provide its best OIP3/P DC performance over a wide input-bias range.

Though GaN HEMTs have primarily been used for power amplification, they are also well suited for receiver applications. In the front-end of receivers, non-linearities, in particular third-order intermodulation products lead to in-band signal distortion. The intermodulation distortion is primarily dominated by transconductance and its derivatives. In this paper, we report on N-polar GaN MIS-HEMTs able to simultaneously achieve high gain (12.7 dB) and excellent linearity performance (OIP3/ $\text{P}_{\mathbf {DC}}$ of 15 dB) for low-power receiver application at 30 GHz. With a two-tone load-pull input-bias sweep, we demonstrate that the linearity of high performance HEMTs is sensitive to bias, and we present our measurement methodology to accommodate this.

In this letter, we report on the demonstration of a Mg-doped GaN/Al0.2Ga0.8N superlattice (SL) based depletion mode p-channel FinFET to improve the on current (ION). A two-step approach involving a dry etch followed by a Tetramethylammonium hydroxide (TMAH) wet etch was employed to obtain fins with minimum width of 50 nm using optical lithography. Normalizing current with fin height, an ION of 52 mA/mm and 110 mA/mm were achieved for 80 and 105 nm wide fins respectively.

Privacy and Trust are critical issues in automation systems/ transportation systems. Today’s Vehicle is need of everyone for moving one place to another. Together this, data security plays an important role in automation systems as critical user’s (vehicle’s user) data is moved to another user though internet with the help of wireless devices and routes which includes optical fiber, radio channels, etc. In fact, each and every device is connected to the internet and is linked to each other, thus forming the Internet of Things (IoT). As the network is moving towards wireless applications, many threats to vehicles (autonomous vehicles) are becoming a critical problem for vehicles users and service providers. A majority of these attacks can be spotted and detected with the hep of a number of intrusion detection techniques which were elucidated in the earlier decade. These techniques are highly efficient in the identification of any form of individual breaches into the system by catching hold of invalid data access. A few of the systems which need safety are an integral part of Wireless Networks which consist of WLANs (Wireless Local Area Networks), WPANs (Wireless Personal Area Networks), etc. WPAN family further constitutes of three networks which are WSNs (Wireless Sensor Networks), mobile phones and RFID (Radio Frequency Identification like On Board Units (OBUs)). Since digitization is taking place in each and every sector, i.e., defence, healthcare, education, automation industries etc., and so the threat to data also exist. In this article, we protect IoT based environment based smart/ Intelligent Transportation Systems (ITS) using a novel concept “Blockchain Technology”. With proposing novel solution called ‘’PChain using Blockchain Technology (BT), we received many benefit in ITS’s applications. We discuss several open issues and challenges for the respective technology in near future (or next decade).

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. The first p-type field-effect transistor (pFET) based on an AlGaN/GaN superlattice (SL), grown using metal-organic chemical vapor deposition (MOCVD), is reported. Magnesium is used as the p-type dopant. A sheet resistance of 11.6 k omega (-1) and a contact resistance of 14.9 omega mm are determined using transmission line measurements (TLMs) for Mg doping of 1.5 x 10(19) cm(-3). Mobilities in the range of 7-10 cm(2) (V s)(-1) and a total sheet charge density in the range of 1 x 10(13)-6 x 10(13) cm(-2) are measured using room temperature Hall effect measurements. Without tetramethylammonium hydroxide (TMAH) treatment, the fabricated pFETs have a maximum drain-source current (I-DS) of 3 mA mm(-1) and an on-resistance (R-ON) of 3.48 k omega mm and do not turn off completely. With TMAH treatment during fabrication, a maximum I-DS of 4.5 mA mm(-1), R-ON of 2.2 k omega mm, and five orders of current modulation are demonstrated.

This letter reports on the improvement of the large-signal W-band power performance of nitrogen-polar gallium nitride deep recess high electron mobility transistors with the addition of a 40-nm-thick ex-situ silicon nitride passivation layer deposited by plasma enhanced chemical vapor deposition. The additional passivation improves the dispersion control allowing the device to be operated at higher voltages. Continuous-wave load pull measurements performed at 94 GHz on a 2 x 37.5 mu m transistor demonstrated an improvement in the peak power-added efficiency (PAE) to 30.2% with an associated output power density of 7.2 W/mm at 20 V drain bias. Furthermore, at 23 V, a new record-high W-band power density of 8.84 W/mm (663 mW) was achieved with an associated PAE of 27.0%.

We report thin, high quality n(+)type doped N-polar GaN contact layers grown using metal-organic chemical vapor deposition with carrier concentration as high as 3.5 x 10(20)cm(-3)and an electron mobility of 80 cm(2)V(-1)s(-1)at room temperature resulting in a low sheet resistance of 57.3 Omega/ and specific contact resistance of 1.7 x 10(-7)Omega.cm(2). These results were obtained via silicon doping of (000 (1) over bar) N-polar GaN grown on 4 degrees miscut sapphire substrates using a flow modulation growth scheme at a deposition temperature of 850 degrees C.

This work presents recent progress in the W-band (94 GHz) power performance of N-polar GaN deep recess HEMTs grown on sapphire substrates. While SiC has been the substrate of choice to achieve the highest level of performance, sapphire substrates are a lower cost alternative. In this work we show that N-polar GaN deep recess HEMTs grown on sapphire match the power performance of a device on SiC up to 14 V with 5.1 W/mm of output power density. At 16 V the device on sapphire starts to suffer from thermal effects but still demonstrated 5.5 W/mm with an associated 20.6% power-added efficiency. This work also examines the impact of encapsulating the device in a low dielectric constant film often used for the implementation of a RF wiring environment.

In this study the MOCVD growth and electrical properties of N-polar modulation doped p-AlGaN/GaN superlattices (SLs) were investigated. Hole sheet charge density and mobility were studied as a function of the concentration of the p-type dopant Mg in the SL and the number of SL periods. Room temperature Hall measurements were carried out to determine the hole mobility and the sheet charge density. While the hole density increased with increasing number of SL periods, the hole mobility was largely unaffected.Hole mobilities as high as 18cm2/Vs at a simultaneous high hole density of 6.5e13 cm-2 were observed for N-polar SLs with a Mg modulation doping of 7.5e18 cm-3. For comparable uniformly doped Ga-polar SL samples, a mobility of 11cm2/Vs was measured. Lowest sheet resistance in the GaN/AlGaN materials system of 5kOhm/sq is also reported. Test-structure transistors were also fabricated to investigate the applicability of these SL structures, with planar device resulting in a current of 5mA/mm, and a FinFET structure resulting in a current of over 100mA/mm.

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 cm2̂/Vs and a total sheet charge density in the range of 1e13-6e13 cm-2 were measured using room temperature Hall effect measurements. Without Tetramethylammonium hydroxide (TMAH) treatment, the fabricated pFETs had a maximum drain-source current (IDS) of 3mA/mm and an On-Resistance (RON) of 3.48 kΩ.mm, and did not turn-off completely. With TMAH treatment during fabrication, a maximum IDS of 4.5mA/mm, RON of 2.2kΩ.mm, and five orders of current modulation was demonstrated, which is the highest achieved for a p-type transistor based on (Al,Ga)N.

Phonon polaritons (PhPs) are long-lived electromagnetic modes that originate from the coupling of infrared (IR) photons with the bound ionic lattice of a polar crystal. Cubic-boron nitride (cBN) is such a polar, semiconductor material which, due to the light atomic masses, can support high-frequency optical phonons. Here we report on random arrays of cBN nanostructures fabricated via an unpatterned reactive ion etching process. Fourier-transform infrared reflection spectra suggest the presence of localized surface PhPs within the reststrahlen band, with quality factors in excess of 38 observed. These can provide the basis of next-generation IR optical components such as antennas for communication, improved chemical spectroscopies, and enhanced emitters, sources, and detectors.