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Development of a crystal-reconstructed semiconductor aptamer photoelectrochemical multi-tumor detection biosensor with ultra-sensitivity via a high-energy laser treatment technique.

AlGaN/GaN Schottky barrier diode (SBD) temperature sensor with low turn-on voltage was fabricated by employing the recessed anode structure. This AlGaN/GaN SBD demonstrates good rectification in a broad temperature scope from 298 to 473 K. Compared with common planar diode, the recessed anode SBD shows a relatively lower turn-on voltage and better Schottky contact characteristics. The temperature-dependent forward voltage at a fixed current displays great linearity, contributing to a sensitivity of about 1.0 mV/K. The calculated sensitivities exhibit the downtrend by increasing current level, which is in agreement with the thermionic emission (TE) model. The recessed anode AlGaN/GaN SBDs show good potential in temperature sensor application.

Photoelectrochemical (PEC) water splitting is considered as an ideal technology to produce hydrogen. Photogenerated carrier migration is one of the most important roles in the whole process of PEC water splitting. It includes bulk transfer inside of the photoelectrode and the exchange at the solid–liquid interface. The energy barriers during the migration process lead to the dramatic recombination of photogenerated hot carrier and the reducing of their redox capacity. Thus, an applied bias voltage should be provided to overcome these energy barriers, which brings the additional loss of energy. Plentiful researches indicate that some methods for the regulation of photogenerated hot carrier, such as p-n junction, unique transfer nanochannel, tandem nanostructure and Z-Scheme transfer structure et al., show great potential to achieve high-efficient PEC water overall splitting without any applied bias voltage. Up to now, many reviews have summarized and analyzed the methods to enhance the PEC or photocatalysis water splitting from the perspectives of materials, nanostructures and surface modification etc. However, few of them focus on the topic of photogenerated carrier transfer regulation, which is an important and urgent developing technique. For this reason, this review focuses on the regulation of photogenerated carriers generated by the photoelectrodes and summarizes different advanced methods for photogenerated carrier regulation developed in recent years. Some comments and outlooks are also provided at the end of this review.

High-performance AlGaN/GaN lateral Schottky barrier diodes (SBDs) with recess structure and dual metal nitride anodes were demonstrated. With high work-function and nonrecess structure, a NiN anode enhances the breakdown voltage (BV), while a TiN anode reduces the turn-on voltage ( ${V}_{ \mathrm{\scriptscriptstyle ON}}$ ) due to its low work-function and contact to the two-dimensional electron gas (2DEG) layer directly on a recess structure. As the length of the NiN anode ( ${L}_{r}$ ) on the nonrecess region decreases from 75 to 3 $\mu \text{m}$ , ${V}_{ \mathrm{\scriptscriptstyle ON}}$ is reduced from 0.56 to 0.30 V, while the reverse leakage current slightly increases from ${3} \times {10}^{-{4}}$ to ${2} \times {10}^{-{3}}$ A/cm2 at the bias of −10 V. The lateral AlGaN/GaN SBD with a ${L}_{r}$ of 3 $\mu \text{m}$ at a distance of cathode–anode ( ${L}_{\text {AC}}$ ) of 20 $\mu \text{m}$ achieves a high BV of 1.62 kV, an ultralow ${V}_{ \mathrm{\scriptscriptstyle ON}}$ of 0.30 V and a small capacitance of 6.0 pF at zero bias with little degradation on ON-resistance, indicating superior potential application in high-frequency and high-power devices.

AlGaN/gallium nitride (GaN) ion-sensitive field-effect transistors (ISFETs) were fabricated as pH sensors. The sensitivity of the AlGaN/GaN ISFETs was evolved with gate recess process and ammonium hydroxide (NH4OH) treatment. By performing the gate recess process, the threshold voltage ( ${V}_{\text {T}}$ ) of the ISFET increased from −3.33 to −0.31 V and the maximum conductance ( ${G}_{\text {M}}$ ) of the ISFET increased from 0.8 to 2 mS, with the current sensitivity of the pH sensor improving from 52.25 to $78.86~\mu \text{A}$ /pH. Further, after performing the ammonium hydroxide treatment, the ${V}_{\text {T}}$ of the ISFET increased from −0.33 to −0.14 V, with the current sensitivity of the pH sensor improving from 78.86 to $84.39~\mu \text{A}$ /pH. To characterize the surface conditions the X-ray photoelectron spectroscopy (XPS) was deployed. The results indicated that many nitrogen vacancies ( ${V}_{\text {N}}$ ) were introduced during the recess process, leading to a negative ${V}_{\text {T}}$ shift and a smaller potential sensitivity ( ${S}_{V}$ ), which can be improved by ammonium hydroxide treatment.

Surface passivation of the photoelectrode by wide bandgap semiconductor quantum layer is an important strategy to improve work stability and surface state inhibition. However, an inevitable energy barrier is generated during the quantum tunneling process of the photocarriers. To overcome this shortage, a tandem photo-generated hole transfer route is fabricated on BiVO

Vertical GaN Schottky barrier diode was fabricated as temperature sensor by using a thermally stable TiN anode. The current-voltage characteristics of the diode measured at various temperature present a zero-temperature coefficient (ZTC) bias point of approximately 0.6 V. At the voltage below the ZTC bias point (sub-threshold region), the forward voltage at a fixed current decreases linearly with the increasing temperature, resulting in a sensitivity of approximately 1.3 mV/K. In the reversely biased region, the leakage current also presents temperature-dependent behavior with a sensitivity of approximately 19.7 mA/K regardless of the bias. Those results can be interpreted by the thermionic emission model.

Near infrared (NIR) energy up-conversion (UC) is an important topic related to sustainable energy harvesting. In NIR UC devices, decreasing the transfer impedance of the photocarrier is an urgent challenge. In this work, we fabricate a NaYF4:Er3+–Yb3+/AZO/Cu2O sandwich-like photocathode device. In this structure, the Al-doped ZnO polycrystal thin film (AZO) interlayer acts as a functional channel for photocarrier transfer and back collection, which can reduce the impedance when photocarriers pass through the NaYF4 layer in a traditional NIR-UC coupled photoelectrode. The AZO layer also acts as a buffer layer to decrease the lattice mismatch at the NaYF4:Er3+–Yb3+ and Cu2O interface, resulting in a lower density of interface defects and higher crystallinity of the Cu2O thin film. Based on the dual functions of the AZO interlayer, this NIR-UC coupled photocathode achieved a recorded photocurrent density of 1.0 mA cm−2 under 980 nm laser (1.0 W cm−2) illumination. Therefore, this is a promising strategy to solve the main issue of very high photocarrier transfer impedance in NIR-UC coupled photoelectrodes.

This article presents a terahertz integrated cavity bandpass filter based on cyclic etched silicon carbon (SiC) via-holes. Solutions are discussed in detail, including design, fabrication, and optimization. The fabrication procedures of the integrated filters are specially optimized, which are fully compatible with that of the common terahertz monolithic integrated circuit. The cyclic via-hole etching technique based on inductively coupled plasma (ICP) is proposed, which achieves via-holes with a controllable inclination on SiC substrate. Measurements show that the insertion loss of the cavity integrated filter is only 1.55 dB at 185 GHz, with a relative bandwidth of 9.7%. Two transmission zeros are introduced by the over-moded technique, achieving the out-of-band suppression of the filter higher than 40 dB. Compared with the traditional terahertz cavity filters, the integrated cavity on SiC substrate provides similar electric performances and better integration but with the one-thousandth of the volume.

This article presents a finger-type gallium nitride (GaN) Schottky barrier diode (SBD)-based microwave rectifier with medium-power capacity and wide power bandwidth. A complete solution including SBD design and fabrication, model extraction, circuit optimization, and demonstration is proposed. The finger-type anode and critical thickness epitaxial layer techniques are adopted to reduce the GaN SBD resistance to 1.9 $\Omega $ (0.011 $\text{m}\sf \Omega \cdot \text {cm}^{{2}}$ ) and achieve nearly constant junction capacitance over a wide range of voltages (17–25 V). Revised equivalent models including the effects of large pads, critical thickness epitaxial layer, and finger-type layout are proposed to describe the new features of the SBD. A 2.45-GHz microwave rectifier based on the GaN SBD is designed and measured, having a maximum power and an efficiency of 1.91 W and 78.5%, respectively. The high-efficiency power range (≥70% and ≥75%) is significantly extended to 14 and 10.8 dB. Finally, a wireless clinical examination prototype constructed by a rectifier, antennas, biomedical sensors, and a signal processer is proposed for demonstration. The resulting wireless electrocardiogram shown in computer is clear and stable.

In this study, we developed a crystal-reconstructed-BiVO

In this work, we fabricate a semitransparent BiVO4 photoanode via the synergistic effect of indium (In) doping and anoxic annealing. An optimized photocurrent density of 3.6 mA cm–2 at 2 V versus r...

Temperature sensor using series GaN Schottky barrier diode (SBD) with TiN anode was fabricated and evaluated extensively. The diode presents good characteristics in a wide temperature range from 25 °C to 200 °C. The temperature dependent forward voltage of the conventional 8-finger SBD at a fixed current shows good linearity, resulting in a sensitivity of approximately 1.14 mV/K. On the other hand, the series SBD with two 8-finger diodes enhances the sensitivity by nearly two times. The enhancement in temperature sensitivity is interpreted using a series model, with the obtained parameters are comparable with the 8-finger SBD.

TiN/GaN Schottky barrier diodes with different anode diameters are fabricated to investigate the temperature sensing mechanism. All the circular diodes present good stability over a temperature range of 25 °C–200 °C. In the fully turn-on region, the sensitivity increases with the increasing diameter. Furthermore, the highest sensitivity of 1.22 mV/K is obtained for a 300- $\mu \text{m}$ -diameter device at current of 20 mA, taking into account the series resistance. In the subthreshold region, the forward current ( ${I}_{D}$ ) density determines the sensor sensitivity, in which a larger current density corresponds to a lower sensitivity. In addition, the strong dependence of the leakage current on the temperature indicates that the linearity of ln ( ${I}_{r}$ ) versus temperature can be also used for sensor applications.

p-NiO/n-GaN heterostructure diodes with different anode diameters were fabricated and comprehensively characterized for temperature sensor application. The circular diodes with NiO anode presented good stability in the temperature range from 25 to 200 °C. It is found that the temperature sensitivity is significantly influenced by the series resistance and ideality factor at the fully-turn-on state. A sensitivity of 2.58 mV/K was achieved for the device with a diameter of 100 $\mu \text{m}$ (at 20 mA) and the sensitivity decreased with the increasing area. In the sub-threshold region, the forward voltage at a current density also varied linearly with temperature. The sensitivity shows high dependence on the forward current density and a smaller current density is corresponding to a higher sensitivity.

AlGaN/GaN heterojunction field-effect transistors (HFETs) with p-GaN cap layer are developed for normally-off operation, in which an in-situ grown AlN layer is utilized as the gate insulator. Compared with the SiN x gate insulator, the AlN/p-GaN interface presents a more obvious energy band bending and a wider depletion region, which helps to positively shift the threshold voltage. In addition, the relatively large conduction band offset of AlN/p-GaN is beneficial to suppress the gate leakage current and enhance the gate breakdown voltage. Owing to the introduction of AlN layer, normally-off p-GaN capped AlGaN/GaN HFET with a threshold voltage of 4 V and a gate swing of 13 V is realized. Furthermore, the field-effect mobility is approximately 1500 cm2⋅V−1⋅s−1 in the 2DEG channel, implying a good device performance.

A novel junction terminal extension structure is proposed for vertical diamond Schottky barrier diodes (SBDs) by using an n-Ga2O3/p-diamond heterojunction. The depletion region of the heterojunction suppresses part of the forward current conduction path, which slightly increases the on-resistance. On the other hand, the reverse breakdown voltage is enhanced obviously because of attenuated electric field crowding. By optimizing the doping concentration, length, and depth of n-Ga2O3, the trade-off between on-resistance and breakdown voltage with a high Baliga figure of merit (FOM) value is realized through Silvaco technology computer-aided design simulation. In addition, the effect of the work functions of the Schottky electrodes is evaluated. The results are beneficial to realizing a high-performance vertical diamond SBD.

In this paper, AlN films grown by magnetron sputtering method have been proposed as the gate insulator layer of AlGaN/GaN high electron mobility transistors (HEMTs) to decrease gate leakage current and suppress the interface trap. The effect of the temperature of substrate on the quality of AlN films have been investigated. By inserting the thin AlN film (35 nm) as a gate insulator layer, the on-state resistance of AlGaN/GaN HEMTs decrease from 11.1 Ω mm to 10.3 Ω mm @V g = 0 V, the current collapse decreases from 16.6% to 3.2%, the gate leakage can be reduced from 1.2 × 10−1A mm−1 to 4.4 × 10−6A mm−1 @V g = 2 V by five orders of magnitude, and the fast interface states disappear and the normal trap density decreases from 0.96–1.3 × 1013 cm−2eV−1 to 1.3–3.4 × 1012 cm−2 eV−1, proving that magnetron-sputtered AlN is an effective way to improve the performance of GaN HEMTs.

In this paper, a terahertz integrated cavity band-pass filter (ICF) based on silicon carbide (SiC) has been proposed. The cascade triplet (CT) topology and over-moded cavity has been utilized to implement out-of-band suppression. Measurement showed that at the center frequency of 185GHz, insertion loss of the ICF is only 1.55dB, with a relative bandwidth of 9.7%. Two transmission zeros (TZs) has been produced, achieving the suppression of the upper side-band of higher than 40dB. Compared with a traditional cavity filter, the ICF is only one-thousandth of the volume with providing similar electric performance and better integration.

In this paper, a ZnSe layer was formed by in-situ conversion on the surface of ZnO nanorod array, and then CdSe layer was transformed from the ZnSe layer by ion exchange method. Subsequently, a p-type poly 3,4-ethylenedioxythiophene (PEDOT) ultrathin conductive layer was deposited on the surface of CdSe by multi-current step deposition method. The separation and transmission processes of the photogenerated carriers were studied by analyzing the results of electrochemical impedance spectroscopy (EIS) and intensity modulated photocurrent/photovoltage spectroscopy (CIMPS/CIMVS). The in-situ growth method could reduce the interface barrier between ZnO and CdSe and optimize the interface exchange process of the photogenerated charge carriers. Meanwhile, the p-n junction constructed between PEDOT and CdSe layer could improve the separation efficiency of the photogenerated charge carriers. Therefore, PEDOT layer significantly promote the photoelectrochemical performance by passivating the surface state of CdSe and suppressing the secondary recombination of the photogenerated charge carriers.

In this work, we investigated the oxide reliability of 4H-SiC (0001) MOS capacitors, the oxide was fabricated about 60 nm by thermal oxidation temperature at 1350°C, the oxides than annealed at different temperatures and times in diluted NO (10% in N2). The 4H-SiC MOS structure was analyzed by C-V and I-V measurement. Compared the J-E curves and Weibull distribution curves of charge-to-breakdown for fives samples under different annealing temperature and time, it shows that the high annealing temperature improves the electrical properties as the lifetime enhanced. The mode value of field-to-breakdown (EBD) for thermal oxides by post-oxide-annealing in NO for 30 min at 1350°C was 10.09 MV/cm, the charge-to-breakdown (QBD) of this sample was the highest in all samples, and the QBD value at 63.2% cumulative failure rate was 0.15 C/cm2. The QBD of the sample annealing at 1200°C for 120 min was 0.06 C/ cm2. The effects of NO annealing in high temperature enhance the lifetime of electrical properties and field-to-breakdown obviously. It can be demonstrated that the annealing temperature as high as 1300°C for 30 min can be used to accelerate TDDB of SiC MOS gate oxide.

We reported that high oxidation temperature is attributed to break Si-C bond and release nitrogen gas to nitrogen ions over 1350°C. The capacitance-voltage characteristics of SiO2/4H-SiC (0001) MOS capacitors fabricated under different thermal oxidation conditions are compared. The dependence of oxidation temperature on device characteristics (such as VFB and ΔVFB) is also analyzed. After a high temperature oxidation, the device reliability of SiC MOS is improved. Such behavior can be attributed to the reduction of the interface traps during high temperature oxidation.

Back-grinding process was applied to the 4H-SiC (0001) epitaxial wafers. We found that the parameters about stress increased after back-grinding process. In our work, the characterization of stress on interface state density (Dit) of SiC/SiO2 was investigated. Furthermore, the absorption of peak frequencies was also observed by fourier transform infrared spectroscopy attenuated total reflection (ATR-FTIR) analysis, and the Dit of SiC/SiO2 was obtained by quasi-static capacitance voltage (QSCV) measurement as well as C-φs method. The above results suggested that the Dit increased with the increasing grinding-induced stress.

Nickel nitride (NiN) electrode was prepared by magnetron reactive sputtering for GaN Schottky barrier diodes (SBDs) application. The X-ray diffraction spectrum of and X-ray photoelectron spectroscopy confirm that Ni 3 N is the dominant phase in the electrode film. Compare with the Ni-SBDs, NiN-SBDs show much better rectification characteristics, in which the Schottky barrier height and the turn-on voltage increase 0.2 eV and 0.18 V, respectively, and the leakage current is reduced by two orders. The temperature-dependent current–voltage characteristics demonstrate that the NiN-SBDs have better thermal stability than that of the Ni-SBDs, owing to the suppression of interface reaction between Ni and GaN. In addition, the thermal stability of the GaN diode with NiN anode is potential for temperature sensing application with the sensitivity of approximately 1.3 mV/K.

A comparison study on electrical performance of Ge pMOSFETs with a GeO x passivation layer formed by ozone post oxidation (OPO) and plasma post oxidation (PPO) is performed. PPO and OPO were carried out on an Al2O3/n-Ge (001) substrate followed by a 5-nm HfO2 gate dielectric in situ deposited in an ALD chamber. The quality of the dielectric/Ge interface layer was characterized by X-ray photoelectron spectroscopy and transmission electron microscopy. The PPO treatment leads to a positive threshold voltage (V TH) shift and a lower I ON/I OFF ratio, implying a poor interface quality. Ge pMOSFETs with OPO exhibit a higher I ON/I OFF ratio (up to four orders of magnitude), improved subthreshold swing, and enhanced carrier mobility characteristics as compared with PPO devices. A thicker Al2O3 block layer in the OPO process leads to a higher mobility in Ge transistors. By comparing two different oxidation methods, the results show that the OPO is an effective way to increase the interface layer quality which is contributing to the improved effective mobility of Ge pMOSFETs.

We fabricate an AlGaN/GaN ion-sensitive field-effect transistor through the photoelectrochemical method for pH sensor application. The photoelectrochemical reaction transforms the AlGaN barrier into oxide, which can deplete the two demensional electron gas to achieve the normally-off operation. Besides, the oxide on the surface enhances the sensitivity to approximately 56.3 mV/pH, a value close to the room temperature Nernstian limit. Based on surface characterization results, the needle-like native oxide (a mixture of Al2O3 and Ga2O3) is transformed into a smooth Al2O3-dominated film. The enhanced surface status and transconductance of the normally-off device is regarded as the possible reason to effective improve the pH sensitivity.