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An analog pulse‐width‐modulation (A‐PWM) Micro‐LED (μLED) pixel circuit based on low‐temperature‐polysilicon (LTPS) thin‐film transistors (TFTs) for mobile displays is proposed. The progressive‐emission mode is implemented using a single Sweep (SW) signal by in‐pixel logic operation circuits. By adjusting the emission time of the progressive‐emission mode, the μLED is biased with the maximum quantum efficiency (EQE). Consequently, the static power consumption of proposed pixels is reduced by 29.2%, compared with conventional schemes.

A compact gate driver using p‐type low‐temperature polycrystalline silicon (LTPS) thin‐film transistors (TFTs) was proposed for Micro‐Light Emitting diodes (μLEDs) display using progressive emission analog pulse‐width modulation (A‐PWM) approach. The gate driver contains a simple waveform shaping module and outputs multiple sweep signals, including SW[n], EM[n], and S[n], by reusing the bootstrap node. Compared with conventional schemes, the proposed gate driver renders static power consumption reduction of the μLED display by 29.2%.

This paper studies high‐resolution AMOLED displays pixel and driving circuits using 3D stacking LTPS and oxide hybrid TFT integration technology systematically. It is demonstrated the OLED display resolution reaches 1167 PPI when the minimum line width/line spacing is reduced to 1 μm/0.5 μm. In addition, peripheral row and column drive circuits for the high display resolution were also illustrated. Good dynamic performance of the designed driving circuits was obtained thanks to the 3D TFTs.

This paper presents a PAM and PWM combined Mini‐LED pixel circuit based on oxide TFTs. In the PAM part, a constant current (1mA) allows Mini‐LEDs work at peak efficiency and reduce power consumption. A source follower structure compensates for ΔVTH and VSS IR rise, which has only one TFT on current path, so that the pixel circuit works at low voltage. In the PWM part, a diode connected structure compensates for ΔVTH. Simulation results show that the current error rate is less than 0.81% when ΔVTH of PAM part is within ±3 V. When VSS rises less than 3 V, the current error rate is less than 7.22%. When ΔVTH of PWM part is +3 V, emission time variation is reduced by 99.29% compared with the circuit without compensation. The supply‐voltage can be reduced from 19.7 V to 15 V thanks to the proposed Mini‐LED pixel circuit.

A pulse‐width‐modulation (PWM) pixel circuit for Micro‐LED display based on low‐temperature poly‐silicon and oxide (LTPO) thin‐film transistor (TFT) is proposed. The PWM falling‐time is reduced to 10 μs, which is only 1/10 of conventional PWM pixel schematics, thanks to the high gain dynamic CMOS inverter for converting data voltage to PWM waveforms and an independent diode‐connected compensation structure for generating constant driving current. The maximum error of PWM conversion and driving current of Micro‐LED is less than 1%, despite VTH shift of oxide TFT ±2 V or VTH variation of LTPS TFT ±1 V. Furthermore, high display resolution above 270 PPI is obtained as the pixel layout reduced to 94 μm×94 μm due to the simplified pixel structure.

Dynamic X‐ray detecting for large area medical imaging requires high‐gain and stable Active Pixel Sensor (APS) circuit integrated with Thin Film Transistors (TFTs). In this paper, the APS circuit using oxide TFTs is studied based on the small‐signal model, and the charge gain and effects of threshold voltage shift (ΔVth) are investigated. Detailed SPICE simulations show the charge gain of the APS circuit of the oxide TFTs is 234 × of that of the conventional a‐Si:H TFT PPS circuit.

A compact gate driver on array (GOA) was proposed for Micro‐Light Emitting diodes (Micro‐LED) display based on progressive‐mode pulse‐width modulation (PWM) using low‐temperature‐polysilicon (LTPS) thin‐film transistors (TFTs). Thanks to outputting line‐by‐line scanning (Scan) and emission control signals (EM) to address switching‐and emission‐transistors in Micro‐LED pixel circuit, the proposed GOA circuit enables an increased emission time by 60% with the frame rate of 120 Hz, compared with the conventional GOA circuit of simultaneous operating mode. Furthermore, the pulse‐width of EM signals are programmable simply by adjusting the number of input pulses.

A pulse-width-modulation (PWM) pixel circuit for Micro-LED displays is proposed based on low-temperature poly-silicon and oxide (LTPO) thin-film transistors (TFTs). The pixel circuit features fast PWM transition, as the PWM falling-time is less than 20 μs thanks to the high-gain dynamic inverter. Furthermore, the proposed pixel circuit can compensate the degradation and non- uniformities of TFT characteristics of LTPO TFTs through auto- zeroing configuration of the dynamic inverter and a diode- connected threshold voltage compensation structure. The error rate of luminous time is less than 3.2% and the error rate of current is less than 1% under VTH shift of oxide TFT ±2 V or LTPS TFT ±1 V.

A gate driver on array (GOA) circuit was proposed for low-temperature polysilicon and oxide (LTPO) thin-film transistor (TFT) hybrid-driven active matrix organic light-emitting diode (AMOLED) displays with both high and low refresh rate operation. The GOA generates multiple types of scanning signals by reusing shift registers so that three signal pulses are output parallelly within a single stage to scan p- and n-type switching TFTs and emission TFT of the AMOLED pixels, respectively, leading to a 30% reduction in the layout area. Furthermore, the pulse-width of the scan signals for the emission TFT can be programed simply by changing the number of input pulses to vary refresh rates. The fabricated GOAs work well even with the pulse width reduced to $2.9 \mathbf {\mu }\text{s}$ .

In this communication, a wideband rectifying metasurface (RMS) for RF energy harvesting (EH) is proposed. By virtue of the two resonant modes of the paralleling metasurface (MS) resonator, it is not only the wideband feature can be obtained but also enables direct impedance matching between the high impedance diode and high impedance MS, eliminating impedance matching. A dc feed structure is proposed where each unit of the MS is connected by the chip inductors, and dc energy can be combined and exported directly, eliminating power combining networks. Then, a $6\times6$ array was designed and fabricated. Experimental results show that the proposed RMS system operates at 5.32–6.66 GHz with a fractional bandwidth (FBW) of 22.4%, and the peak efficiency is 74.5%. As a contribution to this work, RF energy on a broader frequency range can be captured by the proposed system with higher system efficiency, while maintaining a simple structure. This shows its great potential in wireless power transfer and indoor RF EH.

This work reports on a piezotronic n-p-n bipolar heterojunction transistor (PBJT) intended for AI-sound recognition with low power consumption footprint. An organic polymer (Poly (3-hexylthiophene)) as Base is sandwiched between two inorganic piezoelectric semiconductor ZnO layers as Emitter and Collector, respectively to form a vertically-stacked heterogeneous n-p-n BJT, which differs from the traditional BJT in that it can provide either current or voltage as an output signal to favor application’s preference. It can be regarded as two back-to-back auto-biased piezotronic heterojunction diodes where Base-Collector diode is reversely biased and Base-Emitter one is in a forward bias (or vice versa) upon sound wave stimuli. In addition, polarized charges generated at Emitter and Collector sides redistribute and as a result, give a significant enhancement in the output voltage. With machine learning AI, low frequency (LF) sound detection, mapping, and recognition have been demonstrated by this device.

A concise pixel circuit with interleaved Emit signals is proposed for active matrix organic light‐emitting diode (AMOLED) displays, on the basis of low‐temperature polycrystalline silicon oxide (LTPO) TFTs. The oxide TFT can be re‐used for both initialization and threshold voltage extraction periods, using interleaved Emit signals of adjacent lines with overlapped waveforms. The proposed pixel circuit consists of 1 oxide TFT and 5 p‐type LTPS TFTs, while only 2~3 types of line‐by‐line scanning driving signals, i.e. the Emit signal and the Scan signal, are required. Implementation of the proposed pixel circuit shows that the occupation can be reduced to 40 μm × 56.7 μm. Furthermore, optimization of the pixel circuit shows the emission current error is less than 2.3% with threshold voltage variation of ± 0.5 V, while refresh rate from 1 to 120 Hz can achieved.

A two‐mode pulse width modulation (PWM) pixel circuit is proposed for Micro‐LED display. The proposed driving method divides the consecutive 8 sub‐frames (256 gray levels) into low‐bit and high‐bit subframes, which are respectively driven by simultaneous emission (SE) and progressive emission (PE) modes. Compared with the traditional PWM driving scheme, the proposed one shows an increased effective luminous time ratio by 40% for a frame rate of 120Hz, which benefits higher power conversion efficiency. There are only 5 dual‐gate metal‐oxide transistors for the pixel circuit, while a source‐follower structure is adopted to extract the threshold‐voltage shift(ΔVth). Simulation results demonstrate that the current error rates can be reduced to 2% with ΔVth of ± 1 V for various grayscales.

A compact integrated gate driver using metal‐oxide TFTs is proposed for Micro‐LED display. The positive pulse generation module (i.e. Scan driver) and negative modules (i.e. Emit driver) are located at different side of the Micro‐LED display, respectively. While Emit signals are re‐used for low‐level‐maintaining of the Scan module, the gate driver design can be much simplified and area occupation of the single gate driver can be reduced to 90 μm(length)× 245 μm(height), while the length of conventional designs exceeds 1000 μm. The simulation results of cascaded gate driver show that the rising time and falling time of the circuit are reduced to 1.3 μs and 2.1 μs, respectively, with the gate loading of 1.5 kΩ and 150 pF.

In this paper, pixel circuit design method using low‐temperature poly‐silicon and oxides (LTPO) thin film transistors (TFTs) for active‐matrix organic light‐emitting diode (AMOLED) are derived in detail. Through calculation and SPICE simulation of a typical 7TFT‐1C LTPO pixel circuit, the optimum value for the capacitor is selected as 0.1 pF for accurate VTHcompensation and high resolution above 490 pixels per inch (PPI). Moreover, to reduce the relative current error rate to 3 %, the maximum allowable threshold voltage shift is limited within −0.98 V and 0.44 V for IGZO TFT, and within −0.3 V to 0.31 V for the driving TFT (LTPS). This research provides guidelines for AMOLED display development using LTPO TFTs.

The a‐IGZO TFTs integrated gate driver circuit with inter‐frame memory module and isolated bootstrapping node structure is proposed for AMOLED display. The driver can provide progressive display signal, inter‐frame detection signal and standby detection signal. Compared with conventional ones, the proposed inter‐frame memory shows enhanced driving ability due to the introduce of voltage bootstrapping function. Besides, the proposed gate driver can tolerate larger threshold voltage variations (ΔVth) than the conventional circuit due to the isolated bootstrap node structure.

This paper demonstrates a novel low‐temperature‐poly‐Si thin‐film transistors (LTPS TFTs) gate driver with tunable width for low‐grey level brightness adjustment of active‐matrix organic light‐emitting diode (AMOLED) display. The width of output pulses can be tuned accordingly by changing the number of input pulses, to avoid changing the frequency, duty ratio, or increasing the numbers of the external clock‐lines. The proposed circuit still works well when outputting 10 ms pulse with leakage current above 1.45 nA.

An OLEDoS microdisplay system is proposed in this paper, which includes a voltage‐driving pixel circuit, an OLED threshold voltage detection method, and a fast‐progressive compensation scheme. The measurement result shows that the range of the programming display voltage of the proposed voltage‐driving pixel circuit is 5.15 times larger than the gate‐source voltage difference of the driving transistor. The measured lowest current of a pixel can be as low as 2.89 pA.

In this work, we proposed a voltage‐programmed AMOLED pixel circuit using amorphous InGaZnO thin‐film transistors (a‐IGZO TFTs). For every display frame, thanks to the capacitive coupling method, the gate‐source voltage of the driving transistor is programmed through a zero to a positive value process, i.e. a unipolar sweeping direction is maintained for the driving transistor, to suppress the electrical hysteresis effects. In addition, the threshold voltage variation of the driving transistor can also be compensated through a source follower structure. Simulation results indicate that the relative current error is less than 30% for threshold voltage variations of ± 0.4 V.

A hydrogenated amorphous silicon (a‐Si:H) gate driver circuit for vehicle displays is proposed. The new gate driver circuit features a separated bootstrapping structure to enhance the driving ability for low operating temperature. Electrical characteristics of the standard a‐Si:H TFTs are measured and modeled with ‐40 °C, 25 °C and 80 °C SPICE simulations of a 6 stages gate driver circuit show that, with the operation temperature of ‐40 °C, the high level of gate driver circuit (i.e. VGH) maintains above 17 V, while VGH is decreased to 0 V for the conventional schematic.

A robust a‐IGZO TFT integrated gate driver for AMOLED is proposed. The emission driver and dynamic inverter share the pull‐up and pull‐down parts, which features enhanced charging and discharging ability. The driver provides not only multiple control signals for internal compensation, but also increased threshold voltage margin.

The a‐IGZO TFTs integrated gate driver being compatible depletion‐mode device is proposed for AMOLEDs. The circuit features a bootstrapping inverter, which is initialized by global signal and controlled by cascading gate‐driving signals. Two sets of clocks with different low voltages are employed. Enhanced stability and reduced power consumption is thus resulted. The circuit can generate ultra‐wide compensation signals for AMOLED displays even with Vthof ‐6 V.

An IGZO TFTs integrated gate driver with an independent bootstrapping structure and an independent control unit is proposed for AMOLED display. The driver can output both programmable multi‐pulse scan signals and normally‐high‐voltage emission control signals. Compared with the traditional bootstrapping node structure with a long rising time of 1.06 µs, and the diode‐connected bootstrapping node structure with a long falling time of 1.60 µs, the proposed driver has a short and symmetric rising and falling time of about 0.64 µs. Cascaded simulation results show that the driver may be applicable to 5.5‐in full HD AMOLED panel.

In this work we present a DC‐DC converter based on metal oxide thin film transistors (TFTs) for passive radio frequency identification (RFID) tags. To increase the voltage conversion ratio, the cross‐coupled structure with positive feedback from adjacent stages is proposed. Compared with conventional DC‐DC converter with separation block, the proposed circuit features the decreased threshold voltage drop, the reduced on‐resistance of switch transistor, the improved driving capability and the increased power efficiency. The simulated results reveal that the output voltage and maximum power efficiency for proposed two‐stage DC‐DC converter are 16.6 V and 52% at a output current of 550 µA, which are 12.6 V and 42% at a output current of 250 µA for conventional designs.

The a‐IGZO TFTs integrated gate driver on array with depletion‐mode compatible is proposed for AMOLEDs. The driver features a bootstrapping inverter, which is initialized by global signal and controlled by cascading signals. Greatly enhanced stability and pull‐down ability of the circuit is thus resulted. The driver functions well even with Vth of ‐5V and ripple on the output is reduced to 27.4%.

A reliable digital thin‐film transistors (TFTs) integrated ambient light sensor is proposed. The circuit structure is simple, as only 6 TFTs and 2 capacitors are required. The intensity of ambient light is presented by the number of voltage pulses at the output terminal of the light sensor. The operating principal of the sensor are detailed, and SPICE simulations are performed to explore the relationship between the number of output pulses and the light‐induced leakage current. The feasibility of the circuit is further proved by measurements of fabricated circuit samples with the standard a‐Si:H TFTs process.

A new OLEDoS pixel circuit is proposed for high resolution micro‐displays with improved image quality. The data voltage range is extended by using two coupling capacitors to raise the voltage at the source electrode of the driving transistor. Furthermore, the image quality is improved by a compensation scheme of the threshold voltage variation of the driving transistor. The simulations on the basis of CSMC 0.25 µm CMOS model are used to verify the performance of the proposed pixel circuit. It is shown that the data voltage of the proposed pixel circuit ranges from 1.5 V to 3.05 V, which is 2.5 times of that of the conventional 2T1C pixel circuit. The emission current error is decreased to −2.6% ~ 2.6% with ±5 mV threshold voltage variation of the driving transistor for the proposed circuit.

An a‐IGZO TFTs integrated gate driver with programmable output waveform for AMOLED display is proposed by shared input shift registers and output stages of multiple clock‐follower structure. The driver provides not only multiple scan and control signals for internal compensation, but also extended scan pulses for external compensation.

A depletion‐mode amorphous indium‐gallium‐zinc‐oxide thin‐film‐transistor (a‐IGZO TFT) gate driver on array (GOA) integrated circuit has been proposed and fabricated for a 15‐inch active‐matrix organic light emitting diode (AMOLED) display in this work. The depletion‐mode a‐IGZO TFTs were turned off completely due to series‐connected two‐transistor structure and dual low‐voltage‐level power signal. For this reason, the window of Vth shift margin was wide with margin value from −5V to +10V by Spice simulation. Additionally, the proposed GOA circuit exhibited stable high‐voltage output pulse. Subsequently, GOA circuit was placed in a 15‐inch AMOLED display and the performance of the proposed circuit was confirmed.

Analysis results demonstrates in this paper for gradation horizontal line (H-line) occurred in reliability (aging) test on amorphous silicon TFT-LCDs with integrated gate driver technology (short as GOA circuit). There are two factors that induce H-line: GOA gate output and data inversion type. Changing these two factors could eliminate or relieve H-line defect.

A novel bootstrap method is proposed, which can significantly reduce the clock feedthrough effect and the dynamic power consumption. An ESL a-IGZO TFTs based gate driver using this technique is designed. It is shown that the ripple voltage and the power consumption of the proposed driver are only 22.9% and 23.86% of those of the earlier driver.

A stack buffer structure is proposed to suppress feed-through effects, which is caused by serious gate-to-drain capacitance of Etching-Stop-Layer (ESL) type InGaZnO (IGZO) TFTs. For low-level-maintaining periods, the stack buffer TFT can be modeled by reversely cascaded diodes for decreasing of noise voltage of internal nodes. Compared with conventional designs, the proposed buffer structure owns better stability and good driving ability. A robust gate driver using the proposed buffer structure is demonstrated, and only 7 TFTs and 1 capacitance are used. Thorough analysis and simulations are carried out, and the circuit performance is discussed concerning threshold voltage variation, different bootstrapping capacitance, and decreased driving pulse width. It is proven that the proposed gate driver is promising for high performance IGZO TFT display with high resolution for large dimension display.

Reliability issues of TFT integrated gate driver are still of great concern for large size (i.e. TV) display applications, especially for a‐Si:H TFT integrated panels with stressing test of high temperature and high humidity (HTHHO). In this paper, current detection method is proposed for gate driver failure identification. Measurements of 55‐inch UHD TV (4K) panel with integrated gate driver are carried out. It is found that gate driver failure after HTHHO are strongly associates with via‐hole open of clock bus‐lines. It is demonstrated that current through clock lines will be increased with prolonged falling edge due to multi‐pulses of gate driver outputs. And clock bus‐line open is caused by oxygen of Cu after long operating time during the stressing test.

A novel super-halo doping concept for nano-scale CMOS application is presented, which features a counter ion implantation performed through the gaps formed at the gate edges. The implantation forms two high localized halo doping (LHD) zones below the source and drain regions adjacent to the channel. The LHD zones effectively shield the source and channel regions from the drain field penetration, ensuring a much improved short-channel effect. The excellent performances of the LHD devices are verified by simulation results. The fabrication process for the LHD devices is also suggested and discussed.

An analytical drain current model based on the surface potential is proposed for amorphous indium gallium zinc oxide (a-InGaZnO) thin-film transistors (TFTs) with a synchronized symmetric dual-gate (DG) structure. Solving the electric field, surface potential (phS), and central potential (ph0) of the InGaZnO film using the Poisson equation with the Gaussian method and Lambert function is demonstrated in detail. The compact analytical model of current-voltage behavior, which consists of drift and diffusion components, is investigated by regional integration, and voltage-dependent effective mobility is taken into account. Comparison results demonstrate that the calculation results obtained using the derived models match well with the simulation results obtained using a technology computer-aided design (TCAD) tool. Furthermore, the proposed model is incorporated into SPICE simulations using Verilog-A to verify the feasibility of using DG InGaZnO TFTs for high-performance circuit designs.

A novel super-halo doping concept for nano-scale CMOS application is presented, which features a counter ion implantation performed through the gaps formed at the gate edges. The implantation forms two high localized halo doping (LHD) zones below the source and drain regions adjacent to the channel. The LHD zones effectively shield the source and channel regions from the drain field penetration, ensuring a much improved short-channel effect. The excellent performances of the LHD devices are verified by simulation results. The fabrication process for the LHD devices is also suggested and discussed.