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In this letter, we report the influence of p-GaN body doping concentration on the ON-state performance of vertical GaN trench MOSFETs. Decreasing the p-GaN body doping concentration leads to an enhanced maximum drain current ( ${I} _{D,\max}$ ), reduced specific ON-resistance ( ${R} _{ \mathrm{\scriptscriptstyle ON},\mathrm{sp}}$ ), but also a decreased threshold voltage ( ${V} _{th}$ ), suggesting that the p-GaN doping plays an important role in balancing the ${V} _{th}$ , ${R} _{ \mathrm{\scriptscriptstyle ON},\mathrm{sp}}$ and ${I} _{D,\max}$ in vertical GaN trench MOSFETs. Resulting from the tuning of Mg concentration in the p-GaN, we demonstrate high ON-performance including a high ${I} _{D,\max}$ of 2.8 kA/cm2, a low ${R} _{ \mathrm{\scriptscriptstyle ON},\mathrm{sp}}$ of 0.87 $\text{m}\Omega \cdot $ cm2, a large ${V} _{th}$ of 4.8 V in a quasi-vertical GaN trench MOSFET on sapphire with a 2.5- $\mu \text{m}$ -thick drift layer, while maintaining a breakdown voltage of 273 V.

A monolithic thin film red light emitting diode (LED) active-matrix (AM) micro-display driven by a complementary metal-oxide semiconductor (CMOS) driver is demonstrated. The resolution of the micro-display is $64\times36$ , with a $40\,\,\mu \text{m}\,\,\times 40\,\,\mu \text{m}$ pixel pitch. Starting from AlGaInP epi-layers grown on GaAs substrates, the monolithic red LED array was fabricated and then integrated with the AM driver using Au/In flip-chip bonding technology. After removal of the GaAs substrate, a crack-free thin film micro-display was realized with a high pixel yield. The thin film red LED AM micro-display delivers a luminance of $2.35\times 10^{4}$ cd/m2 at full-load conditions and can render images with 4-bit grayscale. This work not only provides a manufacturing-friendly approach for monolithic thin film red LED micro-displays, but also brings the possibility of hybrid integration with blue/green LEDs to achieve full-color LED micro-displays.

Investigation of high-performance lasers monolithically grown on silicon (Si) could promote the development of silicon photonics in regimes other than the 1.3 -1.5 µm band. 980 nm laser, a widely used pumping source for erbium-doped fiber amplifier (EDFA) in the optical fiber communication system, can be used as a demonstration for shorter wavelength lasers. Here, we report continuous wave (CW) lasing of 980 nm electrically pumped quantum well (QW) lasers directly grown on Si by metalorganic chemical vapor deposition (MOCVD). Utilizing the strain compensated InGaAs/GaAs/GaAsP QW structure as the active medium, the lowest threshold current obtained from the lasers on Si was 40 mA, and the highest total output power was near 100 mW. A statistical comparison of lasers grown on native GaAs and Si substrates was conducted and it reveals a somewhat higher threshold for devices on Si. Internal parameters, including modal gain and optical loss are extracted from experimental results and the variation on different substrates could provide a direction to further laser optimization through further improvement of the GaAs/Si templates and QW design. These results demonstrate a promising step towards optoelectronic integration of QW lasers on Si.

To realize fully integrated silicon photonics (Si photonics), reliable III–V light sources that can be efficiently coupled with Si/SiN waveguides are essential. Here, based on a monolithic InP/silicon-on-insulator (SOI) platform, we developed a selective regrowth scheme and constructed a regrowth platform for on-chip lasers that can be efficiently coupled with Si/SiN waveguides. InP and InGaAs/InP multi-quantum wells (MQWs) were regrown on the regrowth template on SOI as well as patterned commercial InP wafers in the same growth run for comparison. A flat (001) top surface after regrowth with a low roughness of 0.38 nm was obtained on SOI. Benefitting from the high quality of MQWs regrowth, strong photoluminescence emission at telecom band can be obtained on both growth templates. Also, multi-wavelength emission on the same chip can be potentially achieved by designing various regrowth openings. Furthermore, the large material volume with vertical stacking structure and intimate placement of MQWs and the Si layer of SOI allow for the potential demonstration of electrically pumped lasers and efficient light coupling between them and Si/SiN waveguides. Therefore, the demonstrated regrowth method provides a promising solution for the monolithic integration of III–V on-chip lasers on Si.

In this work, we demonstrated that ${p}$ -type and ${n}$ -type conduction could be induced in unintentionally doped pristine monolayer (ML) WS2 by forming a hybrid WS2/InGaN quantum dots (QDs) heterostructure, in which the ML-WS2 is partially covered by few-layer graphene. Under illumination, the photo-generated holes or electrons in the QDs were injected vertically into the ML-WS2 and then transported laterally therein. The polarity of the WS2 channel can be controlled by the bias applied to the graphene electrode. This work provides a potential approach to develop ambipolar devices of ML transition metal dichalcogenides through photocarrier doping.

Epitaxially integrating III-V lasers with Si-photonics is the key for compact, efficient, and scalable photonic integrated circuits (PICs). Here we present an investigation of a path forward in integrating III-V functionalities on industry-standard silicon-on-insulator (SOI) platforms using selective area hetero-epitaxy. Based on our recently developed methods of selectively growing device quality InP on (001)-oriented SOI wafers, we demonstrated InP stripes and segments, with dimensions varying from a few hundred nanometers to a few micrometers. The flexible epitaxy of InP on SOI together with the unique “bufferless” trait will enable efficient light interfacing with Si-based photonic devices using either evanescent or butt coupling schemes. We simulated the possibility of employing the micrometer-scale InP on insulator to realize electrically driven lasers and found that the metal induced optical loss is negligible when the InP dimension exceeds 4.0 μm. The potential of utilizing this selective area growth method to realize fully integrated Si-photonics is illustrated.

In this article, we demonstrate normally-OFF p-GaN gate high electron mobility transistors (HEMTs) on Si with an ultrahigh breakdown voltage ( ${V}_{BR}$ ) and excellent saturation drain current. Benefiting from the optimized material growth of high-resistivity buffer, effective Al2O3 surface passivation with suppressed OFF-state leakage current, and proper management of the electric field on the p-GaN gate edge, the device with a gate–drain distance of $18.5~\mu \text{m}$ exhibits a ${V}_{BR}$ of 1344 V at ${I}_{D}$ of $1~\mu \text{A}$ /mm with grounded substrates, the highest among all the reported normally-OFF GaN-on-Si transistors. Well-restored high-density 2-D electron gas and efficient gate modulation enable the device with a high ${I}_{DS,max}$ of 450 mA/mm and a low specific ON-resistance of 3.92 $\text{m}\Omega \cdot $ cm2. Moreover, a large threshold voltage of 1.6 V (at ${I}_{D}$ of $10~\mu \text{A}$ /mm) and a steep subthreshold slope of 66 mV/dec have been achieved, with negligible threshold voltage shift upon long-term forward gate stress at 150 °C. These results illustrate the great potential of p-GaN gate HEMTs on Si for beyond 600-V applications.

Full-color micro-LED displays are being widely developed and regarded as a primary option in current microdisplay technologies to fulfill the urgent demands of metaverse applications in the next decade. In this paper, a monolithic full-color micro-LED microdisplay with a resolution of 423 pixels per inch is demonstrated through the integration of a blue GaN-on-Si display module and a quantum dots photoresist (QDs-PR) color conversion module. The 400 × 240 active-matrix blue micro-LED display with a dominant wavelength of 440 nm was monolithically fabricated using GaN-on-Si epiwafers and flip-chip bonded on a custom-designed complementary metal-oxide semiconductor backplane. A color conversion module was independently fabricated on a 4-in. sapphire substrate by applying red and green QDs-PR arrays and a color filter array through the standard lithography process. Combining the blue GaN-on-Si micro-LED display module and the lithography-based QDs-PR color conversion module, a full-color micro-LED display was achieved with a wide color gamut up to 104% of the standard red, green, and blue and a maximum brightness of over 500 nits. The influence of blue light leakage resulting from the possible misalignment of flip-chip bonding and crosstalk in the bottom GaN-on-Si display was investigated in which the percentages of efficient pumping light for the blue, green, and red subpixels are around 95%, 89%, and 92%, respectively. This prototype demonstrates potential scalability and low-cost volume production of high-resolution full-color micro-LED microdisplays soon.

This article reports trap-related forward conduction instability of GaN quasi-vertical p-i-n diodes grown on a Si substrate. Three hole traps with activation energies of 0.38, 0.60, and 0.70 eV together with one electron trap with an energy level of 0.26 eV under the conduction band were revealed by deep-level transient spectroscopy (DLTS). Pulsed ${I}$ – ${V}$ measurements were performed on a device whose traps were prefilled. The rest time durations and OFF-state bias levels and periods were varied to investigate the forward ${I}$ – ${V}$ recovery phenomenon, which was highly correlated with the carrier detrapping process inside the device. The detrapping process could be greatly accelerated by a reverse bias or a lifted temperature. An “on-the-fly” resistance characterization was carried out to study the time-dependent carrier release process using short positive voltage pulses. The device was further submitted to switch-on transient assessment to investigate the time-resolved dynamic ${R}_{ \mathrm{\scriptscriptstyle ON}}$ evolution. The initial dynamic ${R}_{ \mathrm{\scriptscriptstyle ON}}$ ratio was proportional to the reverse bias level and duration and was gradually decreased after continuous carrier injection until the trapping effects were overwhelmed. With a forward voltage slightly higher than the threshold voltage, it took dozens of milliseconds for the dynamic ${R}_{ \mathrm{\scriptscriptstyle ON}}$ to be equal to its static counterpart. It was found that at 350 K, the ON-resistance ratio could reach unit more rapidly than the room temperature case, indicating mitigation of current collapse of p-i-n diodes and their great potential for high-temperature switching applications.

This letter reports on the suppression of reverse leakage current ( ${I} _{r}$ ) in $\beta $ -Ga2O3 Schottky barrier diodes (SBDs) through Schottky barrier modification by a low power CF4-plasma treatment prior to Schottky metal deposition. Revealed by an x-ray photoelectron spectroscopy (XPS) analysis, the fluorine-plasma treatment brought an incorporation of fluorine ions and depletion of silicon donors in the near surface region of the $\beta $ -Ga2O3, and thus raised its surface potential by around 0.14 eV. Furthermore, insulating GaF x was likely created at the Schottky interface. Attributed to the fluorine-plasma- modified Schottky barrier, a reduced ${I} _{\mathbf {r}}$ by around four orders of magnitude and enhanced blocking voltage ( ${V} _{{block}}$ ) from 150 V to 470 V at ${I} _{r} = 100\mu $ A/cm2 have been achieved without degrading the forward characteristics. Different from the untreated device whose ${I} _{r}$ was purely governed by the thermionic field emission (TFE), the fluorine-plasma-treated SBD showed a greatly suppressed TFE-current until a space-charge limited current (SCLC) started to dominate at around −500 V.

High performance NiO/ $\beta $ -Ga2O3 heterojunction pn diodes were realized by applying a sputtered p-type NiO film onto a lightly doped n-type $\beta $ -Ga2O3 epitaxial layer. Taking advantage of the high barrier height against carriers within the pn heterojunction, the demonstrated device exhibited a high breakdown voltage ( ${V}_{B}{)}$ of 1059 V without optimized electric field management techniques, and before breakdown the reverse leakage current density remained below $1~\mu \text{A}$ /cm2. Simultaneously, a relatively low specific on-resistance ( $R_{\text {on, sp}}{)}$ of 3.5 $\text{m}\Omega \cdot \text {cm}^{{2}}$ was achieved. The built-in potential of the heterojunction that determined by a capacitance-voltage ( ${C}$ - ${V}$ ) measurement was around 2.4 eV. As discussed in terms of the energy band diagram of a type-II heterojunction, the conduction band and valence band offsets at the NiO/ $\beta $ -Ga2O3 hetero-interface were estimated to be 1.2 and 2.3 eV, respectively.

III-Nitride single nanowire (NW)-based p–i–n diode was fabricated using a top–down etching method and its electrical and optoelectronic characteristics were investigated from room temperature to hi...

A three-fold reduction of threshold current, with a minimum threshold current density of 286 A/cm 2 , a maximum operating temperature of 80 °C, and a maximum 3 dB bandwidth of 5.8 GHz was achieved for 1.3 μm InAs quantum dot lasers on patterned, on-axis (001) Si. This was enabled by the reduced threading dislocation density (from 7×10 7 to 3×10 6 cm −2 ), and optimized probe design. The patterned Si produced antiphase domain free material in the coalesced GaAs buffer layer with reduced misfit/threading dislocation nucleation, without the use of Ge/GaP buffers or substrate miscut. Utilizing aspect ratio trapping, cyclic thermal annealing, and dislocation filter layers, high quality III-V on Si devices were grown, demonstrating the compelling advantages of this patterned Si template for a monolithic Si photonics integration platform.