This letter reports an enhancement-mode (E-mode) GaN transistor technology which has been demonstrated to operate in a simulated Venus environment (460 °C, ~ 92 atm., containing CO ₂ /N ₂ /SO ₂ etc.) for 10 days. The robustness of the W/p-GaN-gate AlGaN/GaN high electron mobility transistor (HEMT) was evaluated by two complementary approaches, (1) in-situ electrical characterization, which revealed proper transistor operation (including E-mode ${V}_{\textit {TH}}$ with $ < {0}.{09}$ V variation) in extreme environments; and (2) advanced microscopy investigation of the device after test, which highlighted the effect of the stress conditions on the epitaxial and device structures. To the best of the authors’ knowledge, this is the first demonstration and comprehensive analysis of E-mode GaN transistors in such harsh environments, therefore establishing the proposed GaN technology as a strong contender for harsh environment mixed-signal electronics.

This article reports on the scaling of GaN complementary technology (CT) on a silicon substrate to push its performance limits for circuit-level applications. The highly scaled self-aligned (SA) p-channel FinFET (a fin width of 20 nm) achieved an ${I}_{D,\text {max}}$ of −300 mA/mm and an ${R}_{ \mathrm{ ON}}$ of $27 \Omega \cdot $ mm, a record for metal organic chemical vapor deposition (MOCVD)-grown III-nitride p-FETs. A systematic study on impact of fin width scaling and recess depth in these transistors was conducted. A new SA scaled n-channel p-GaN-gate FET (n-FET) process, compatible with the p-FinFET, demonstrated enhancement-mode (E-mode) n-FETs ( ${L}_{G} = {200}$ nm, ${I}_{D,\text {max}} = {525}$ mA/mm, and ${R}_{ \mathrm{ ON}}={2}.{9}\,\,\Omega \cdot $ mm) on the same epitaxial platform. The p-FETs and n-FETs feature competitive performance in their respective categories and, when taken together, offer a leading solution for GaN CT on a silicon substrate.

This Letter reports the stability of regrown and alloyed Ohmic contacts to AlGaN/GaN-on-Si high electron mobility transistors (HEMTs) for high temperature applications up to 500 °C. Transfer length method (TLM) measurements from 25 to 500 °C in air show that the regrown contacts appear to be stable up to 500 °C during short term (approximately 1 h) testing, while alloyed contacts appear to decrease in contact resistance from 300 to 500 °C though increases in the error bounds due to increase sheet resistance make it difficult to conclude definitely. Additionally, longer term testing shows both technologies remain stable at least up to 48 h at 500 °C, after which the large increase in sheet resistance makes the measurement uncertainty too large to conclude definitively. Advanced microscopy images indicate both the regrown and alloyed contact regions remain structurally intact after prolonged high temperature exposure with no visible degradation in crystallinity or metal composition.

This Letter reports the device and material investigations of enhancement-mode p-GaN-gate AlGaN/GaN high electron mobility transistors (HEMTs) for Venus exploration and other harsh environment applications. The GaN transistor in this work was subjected to prolonged exposure (11 days) in a simulated Venus environment (460 °C, 94 bar, complete chemical environment including CO2/N2/SO2). The mechanisms affecting the transistor performance and structural integrity in harsh environment were analyzed using a variety of experimental, simulation, and modeling techniques, including in situ electrical measurement (e.g., burn-in) and advanced microscopy (e.g., structural deformation). Through transistor, Transmission Line Method (TLM), and Hall-effect measurements vs temperature, it is revealed that the mobility decrease is the primary cause of reduction of on-state performance of this GaN transistor at high temperature. Material analysis of the device under test (DUT) confirmed the absence of foreign elements from the Venus atmosphere. No inter-diffusion of the elements (including the gate metal) was observed. The insights of this work are broadly applicable to the future design, fabrication, and deployment of robust III-N devices for harsh environment operation.

This work proposes a multimetal gated (MMG) architecture to improve the linearity of AlGaN/GaN high-electron-mobility transistor (HEMT). The general idea of this architecture is to use different gate metals along the width of the device. Through experimentally calibrated technology computer-aided design (TCAD) simulation, a selection of metals along with widths that yields the lowest value of third-order transconductance ( ${g}_{m{3}}$ ) has also been estimated. Single-tone large-signal simulation of proposed device exhibits an output-referred 1-dB compression point ( ${P}_{\text {1 dB}}$ ) of 1.81 W/mm, a saturation output power ( ${P}_{\text {sat}}$ ) of 6.91 W/mm, and a maximum power added efficiency (PAE) of 65%, all of which are better than simulations of standard/baseline device structures. Two-tone large-signal simulation shows excellent linearity performance when biased at deep class AB showing OIP3/ ${P}_{\text {dc}}$ of 13.7 dB, which is 6.3 dB higher, and IMD3 of −45.7 dBc, which is 12.9 dB lower than baseline device at ${V}_{\text {DS},{Q}}={28}$ V and ${I}_{D,{Q}}={73}$ mA/mm. These performance matrices attest to the improved linearity performance of the proposed device compared to conventional planar AlGaN/GaN HEMT.

Although graphene has been the primary material of interest recently for spontaneous emission engineering through the Purcell effect, it features isotropic and thickness-independent optical properties. In contrast, the optical properties of black Phosphorus (BP) are in-plane anisotropic; which supports plasmonic modes and are thickness-dependent, offering an additional degree of freedom for control. Here we investigate how the anisotropy and thickness of BP affect spontaneous emission from a Hydrogenic emitter. We find that the spontaneous emission enhancement rate i.e. Purcell factor (PF) depends on emitter orientation, and PF at a particular frequency and distance can be controlled by BP thickness. At lower frequencies, PF increases with increasing thickness due to infrared (IR) plasmons, which then enhances visible and UV far-field spectra, even at energies greater than 10 eV. By leveraging the thickness and distance-dependent PF, deep UV emission can be switched between 103 nm or 122 nm wavelength from a Hydrogenic emitter. Additionally, we find that doping can significantly tune the PF near BP and this alteration depends on the thickness of the BP. Our work shows that BP is a promising platform for studying strong plasmon-induced light-matter interactions tunable by varying doping levels, emitter orientation, and thickness.