arXiv subjects

Nidhin Kurian Kalarickal

Publications and source records attributed to Nidhin Kurian Kalarickal.

13 recordsLinked to original sources

arXiv2026

Sub-Micron Gate $β-Ga_{2}O_{3}$ FinFETs with Current Density $>$ 750 mA/mm and Ion/Ioff Ratio $>$ $10^{9}$

In this work, we demonstrate submicron-gate $β-Ga_{2}O_{3}$ FinFETs that integrate Si delta-doped channels with selectively regrown n++ source/drain contacts. The devices employ 100 nm-wide fins to improve electrostatic control of a high sheet charge density channel of $3.3\times 10^{13}$ cm-2. A 150 nm-gate-length FinFET exhibits a maximum drain current density of 764 mA/mm at VGS = 1 V and VDS = 10 V, an on-resistance of 9.1 $Ω$.mm, and an Ion/Ioff ratio exceeding $10^9$. The device also shows a peak transconductance of 43 mS/mm and de-embedded $f_{T}/f_{MAX}$ values of 6.3/2.0 GHz. Pulsed I-V measurements indicate ~20 % current collapse, attributed primarily to trapping at etched fin sidewalls and the $Al_{2} O_{3}$/ $β-Ga_{2}O_{3}$ interface. These results show that delta-doped $β-Ga_{2}O_{3}$ FinFETs can simultaneously achieve high drive current, strong current modulation, and GHz-frequency operation, providing a scalable device platform for future power and RF electronics.

physics.app-ph↗

arXiv2026

$β-(Al_{0.19} Ga_{0.81})_2 O_3/Ga_2 O_3$ Modulation-Doped Field-Effect Transistors with $>$ 6 kV Breakdown

$β-(Al_{0.19} Ga_{0.81})_2 O_3/Ga_2 O_3$ modulation-doped field-effect transistors (MODFETs) incorporating a high-quality Al2O3 gate dielectric and SiNx passivation are demonstrated for high-voltage operation. The devices exhibited a maximum drain current of 54 mA/mm, an on-resistance of 149 Ohm.mm, a minimum subthreshold slope of 94 mV/dec, and an ION/IOFF ratio exceeding $10^8$. Three-terminal breakdown measurements performed in Flourinert demonstrated a breakdown voltage that increased with gate-drain spacing, reaching 6.6 kV for a device with LGD = 28 microns. The corresponding average lateral electric field approached 2.4 MV/cm, while a power figure of merit of 222 MW/cm2 was achieved. To the best of the authors knowledge, the demonstrated breakdown voltage represents the highest reported value for a $β-(Al_x Ga_{1-x})_2 O_3/Ga_2 O_3$ MODFET and highlights the potential of modulation-doped $β$-Ga2O3 heterostructures for next-generation multi-kV power devices.

cond-mat.mtrl-sci↗

arXiv2026

Temperature Dependent Characteristics of Quasi-vertical AlN Schottky Diodes on Bulk AlN Substrate

We report on the fabrication and temperature-dependent characterization of MOCVD-grown quasi-vertical AlN Schottky barrier diodes (SBDs) on bulk AlN substrates. The SBDs exhibited high current densities exceeding 2 kA/cm2 at 10 V, with a turn-on voltage of ~3.0 V (at 1 A/cm^2) and an on/off ratio >10^9 at room temperature. Stable rectifying operation was maintained up to 300 C (the highest measured temperature), with a pronounced increase in current density at elevated temperatures due to thermally activated carrier transport, accompanied by an increase in extracted Schottky barrier height and a reduction in ideality factor. Capacitance voltage measurements showed strong temperature dependence due to the deep donor nature of Si in AlN, resulting in an increase in the net donor concentration (ND-NA) from ~5x10^17 cm-3 at 300 K to ~1x10^18 cm-3 at 373 K. Temperature-dependent reverse-bias characteristics were consistent with Poole-Frenkel emission as the dominant leakage mechanism, with an estimated trap energy of ~0.34 eV. Characterization using transmission electron microscopy and energy-dispersive X-ray spectroscopy revealed a ~5 nm AlNxOy interfacial layer at the metal/semiconductor junction, which likely influences both forward and reverse transport. These results provide insight into carrier transport, leakage mechanisms, interface chemistry, and high-temperature characteristics, and guidance for the future development of high-performance AlN power devices.

physics.app-ph↗

arXiv2025

Beta-Ga2O3 Sub-Micron FinFETs with Si Delta-Doped Channel Modulating Charge Density Above 3x10^13 cm^-2

This letter reports on the design and demonstration of high-performance Beta-Ga2O3 FinFETs utilizing MOCVD-grown Si delta-doped channels to achieve enhanced carrier transport and electrostatic control. A record high sheet charge density of 3.3x10^13 cm^-2 was modulated using 100 nm fin channels, delivering a peak drain current of 410 mA/mm and a peak transconductance of 60 mS/mm. The FinFET architecture enables strong gate modulation, achieving a high Ion/Ioff ratio between 10^8 and 10^9. A low contact resistance of 0.42 ohm.mm was achieved to the Si delta-doped channel using MOCVD contact regrowth. Small-signal RF characterization revealed a current-gain cutoff frequency (fT) of 3.8 GHz and a maximum oscillation frequency (fMAX) of 2.1 GHz for a 0.8-micrometer gate length. These results demonstrate the efficacy of combining precision delta-doping with a 3D FinFET geometry for high-frequency Beta-Ga2O3 electronics, establishing a platform for future RF and high-power applications

physics.app-ph↗

arXiv2025

Demonstration of KV-Class \b{eta}-Ga2O3 Trench Junction Barrier Schottky Diodes with SpaceModulated Junction Termination Extension

In this work, we report on the design and fabrication of p-NiO/Ga2O3 trench junction barrier schottky diodes (JBSD) integrated with space-modulated junction termination extension (SM-JTE) and compare the performance with planar Ni/Ga2O3 schottky diodes (SBDs) and p-NiO/Ga2O3 heterojunction diodes (HJDs). The JBSDs achieved breakdown voltages exceeding 1.8 kV along with low leakage currents (<10-2 A/cm2), while displaying low turn on voltage (VON) of ~1V, which is similar to that of planar Ni/Ga2O3 SBDs. The fabricated devices showed excellent forward characteristics with low differential on-resistance (Ron,sp) ranging from 4-10.5 mΩ-cm2, for fin width between 0.6- 1.25 microns. Best performing device with fin width of 0.85μm showed a unipolar figure of merit (FOM) of ~0.7GW/cm2. This work showcases the benefits of trench JBS design along with SM-JTE edge-termination for efficient high-performance kilovolt-class \b{eta}- Ga2O3 diodes.

physics.app-ph↗

arXiv2024

>3kV NiO/Ga2O3 Heterojunction Diodes with Space-Modulated Junction Termination Extension and Sub-1V Turn-on

This work demonstrates high-performance vertical NiO/Ga2O3 heterojunction diodes (HJDs) with a 2-step space-modulated junction termination extension. Distinct from the current state-of-the-art Ga2O3 HJDs, we achieve breakdown voltage exceeding 3 kV with a low turn on voltage (VON) of 0.8V, estimated at a forward current density (IF) of 1 A-cm-2. The measured devices exhibit excellent turn-on characteristics achieving 100 A-cm-2 current density at a forward bias of 1.5V along with a low differential specific on-resistance (Ron,sp) of 4.4 mΩ-cm2. The SM-JTE was realized using concentric NiO rings with varying widths and spacing that approximates a gradual reduction in JTE charge. The unipolar figure of merit (FOM) calculated exceeds 2 GW-cm2 and is among the best reported for devices with a sub-1V turn-on. The fabricated devices also displayed minimal change in forward I-V characteristics post reverse bias stress of 3 kV applied during breakdown voltage testing.

physics.app-ph↗

arXiv2024

In-situ Patterned Damage-Free Etching of 3-Dimensional Structures in \b{eta}-Ga2O3 using Triethylgallium

In this work, we report on the anisotropic etching characteristics of \b{eta}-Ga2O3 using triethylgallium (TEGa) performed in-situ within an MOCVD chamber. At sufficiently high substrate temperature, TEGa can act as a strong etchant for \b{eta}-Ga2O3 utilizing the suboxide reaction between Ga and Ga2O3. We observe that due to monoclinic crystal structure of \b{eta}-Ga2O3, TEGa etching on both (010) and (001) substrates is highly anisotropic in nature, both in terms of sidewall roughness and lateral etch rate. Smooth sidewalls are only obtained along crystal orientations that minimize sidewall surface energy. Utilizing this technique we also demonstrate deep sub-micron fins with smooth sidewalls and high aspect ratios. Furthermore, we also demonstrate the damage free nature of TEGa etching by fabricating Schottky diodes on the etched surface which display no change in net donor concentration.

cond-mat.mtrl-sci↗

arXiv2023

$β$-Ga$_2$O$_3$ Trench Schottky Diodes by Novel Low-Damage Ga-Flux Etching

$β$-Ga$_2$O$_3$ trench Schottky barrier diodes fabricated through a Gallium atomic beam etching technique, with excellent field strength and power device figure of merit, are demonstrated. Trench formation was accomplished by a low-damage Ga flux etch that enables near-ideal forward operating characteristics that are independent of fin orientation. The reverse breakdown field strength of greater than 5.10 MV/cm is demonstrated at breakdown voltage as of 1.45 kV. This result demonstrates the potential for Ga atomic beam etching and high-quality dielectric layers for improved performance in $β$-Ga$_2$O$_3$ vertical power devices.

physics.app-ph↗

arXiv2021

Planar and 3-dimensional damage free etching of $β$-Ga2O3 using atomic gallium flux

In-situ etching using Ga flux in an ultra-high vacuum environment like MBE is introduced as a method to make high aspect ratio 3 dimensional structures in $β$-Ga2O3. Etching of $β$-Ga2O3 due to excess Ga adatoms on the epilayer surface had been viewed as non-ideal for epitaxial growth especially since it results in plateauing and lowering of growth rate. In this study, we use this well-known reaction from epitaxial growth to intentionally etch $β$-Ga2O3. We demonstrate etch rate ranging from 2.9 nm/min to 30 nm/min with the highest reported etch rate being only limited by the highest Ga flux used. Patterned in-situ etching is also demonstrated and used to study the effect of fin orientation on the sidewall profiles and dopant (Si) segregation on the etched surface. Using in-situ Ga etching, we also demonstrate 150 nm wide fins and 200 nm wide nano pillars with high aspect ratio. This new etching method could enable future development of highly scaled vertical and lateral 3D devices in $β$-Ga2O3.

cond-mat.mtrl-sci↗

arXiv2020

Electrostatic Engineering using Extreme Permittivity Materials for Ultra-wide Bandgap Semiconductor Transistors

The performance of ultra-wide band gap materials like $β$-Ga$_\mathrm{2}$O$_\mathrm{3}$ is critically dependent on achieving high average electric fields within the active region of the device. In this report, we show that high-k gate dielectrics like BaTiO$_\mathrm{3}$ can provide an efficient field management strategy by improving the uniformity of electric field profile in the gate-drain region of lateral field effect transistors. Using this strategy, we were able to achieve high average breakdown fields of 1.5 MV/cm and 4 MV/cm at gate-drain spacing (L$_\mathrm{gd}$) of 6 um and 0.6 um respectively in $β$-Ga$_\mathrm{2}$O$_\mathrm{3}$, at a high channel sheet charge density of 1.8x10$^\mathrm{13}$cm$^\mathrm{-2}$. The high sheet charge density together with high breakdown field enabled a record power figure of merit (V$^\mathrm{2}$$_\mathrm{br}$/R$_\mathrm{on}$) of 376 MW/cm$^\mathrm{2}$ at a gate-drain spacing of 3 um.

physics.app-ph↗

arXiv2019

Metal$/BaTiO_{3}/β-Ga_{2}O_{3}$ Dielectric Heterojunction Diode with 5.7 MV/cm Breakdown Field

Wide and ultra-wide band gap semiconductors can provide excellent performance due to their high energy band gap, which leads to breakdown electric fields that are more than an order of magnitude higher than conventional silicon electronics. In materials where p-type doping is not available, achieving this high breakdown field in a vertical diode or transistor is very challenging. We propose and demonstrate the use of dielectric heterojunctions that use extreme permittivity materials to achieve high breakdown field in a unipolar device. We demonstrate the integration of a high permittivity material BaTiO3 with n-type $β$-Ga2O3 to enable 5.7 MV/cm average electric field and 7 MV/cm peak electric field at the device edge, while maintaining forward conduction with relatively low on-resistance and voltage loss. The proposed dielectric heterojunction could enable new design strategies to achieve theoretical device performance limits in wide and ultra-wide band gap semiconductors where bipolar doping is challenging.

cond-mat.mtrl-sci↗

arXiv2019

High electron density $β-(Al_{0.18}Ga_{0.82})_2O_3/Ga_2O_3$ modulation doping using ultra-thin (1 nm) spacer layer

We report on the design and demonstration of $β-(Al_{0.18}Ga_{0.82})_2O_3/Ga_2O_3$ modulation doped heterostructures to achieve high sheet charge density. The use of a thin spacer layer between the Si delta-doping and heterojunction interface was investigated in $β-(Al_{0.18}Ga_{0.82})_2O_3/Ga_2O_3$ modulation doped structures. We find that that this strategy enables higher 2DEG sheet charge density up to 6.1x10^12 cm^2 with mobility of 147 cm^2/Vs. The presence of a degenerate 2DEG channel was confirmed by the measurement of low temperature effective mobility of 378 cm^2/V-s and a lack of carrier freeze out from low temperature capacitance voltage measurements. The electron density of 6.1x10^12 cm^2 is the highest reported sheet charge density obtained without parallel conduction channels in an $(Al_{0.18}Ga_{0.82})_2O_3/Ga_2O_3$ heterostructure system.

physics.app-ph↗

arXiv2019

Mechanism of Si doping in Plasma Assisted MBE Growth of \b{eta}-Ga2O3

We report on the origin of high Si flux observed during the use of Si as a doping source in plasma assisted MBE growth of \b{eta}-Ga2O3. We show on the basis of secondary ion mass spectroscopy (SIMS) analysis that Si flux is not limited by the vapor pressure of Si but by the formation of volatile SiO. The low sublimation energy of SiO leads to weak dependence of the SiO flux of Si cell temperature and a strong dependence on the background oxygen pressure. Extended exposure to activated oxygen results in reduction of SiO flux due to the formation of SiO2 on the Si surface. The work reported provides key understanding for incorporating Si into future oxide-based semiconductor heterostructure and device MBE growth.

physics.app-ph↗