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In this work, characterizations are performed to investigate the stability of an mm-wave GaN metal-insulator-semiconductor HEMT. Bias temperature instability (BTI) experiment conducted at various voltages and temperatures show a highly stable threshold voltage (${V}_{\text {TH}}$) with both positive BTI (PBTI) and negative BTI (NBTI) attributing to the high quality of SiN gate dielectric. In addition, ${V}_{\text {TH}}$ shift (${\Delta } {V}_{\text {TH}}$) under reverse-bias step-stress is further monitored, achieving small ${\Delta } {V}_{\text {TH}} < {0.1}$ V and a recoverable behavior below ${V}_{\text {D}}$ , stress = 60 V. After 104 s of stress at 175°C, under the OFF-state high drain-bias, ${\Delta } {V}_{\text {TH}}$ is 0.15 V, and a larger ${V}_{\text {TH}}$ shift (0.23 V) is observed under On-state drain-bias of 28 V due to the high electric-field. According to the time-dependent dielectric breakdown prediction, +3.0 V gate voltage stress at a failure rate of 0.01 % can be extrapolated for mm-wave MIS-HEMT. These findings guarantee a good stability for the device utilized in power amplifier applications. [ABSTRACT FROM AUTHOR]

A drain-controlled current-mode deep level transient spectroscopy (I-DLTS), was developed for investigation of Semi-ON-state current collapse in AlGaN/GaN high electron mobility transistors (HEMTs). By inserting a graded AlGaN back-barrier between the GaN channel and AlGaN buffer layer, hot-electron effect induced charging of buffer traps is effectively blocked, which contributes to a remarkable suppressed current collapse in AlGaN/GaN HEMTs under Semi-ON-state stress. A broad-distributed electron trap ${E}_{\text {T1}}$ , which features an energy level depth ${E}_{\text {C}}$ - ${E}_{\text {T}}$ and apparent capture cross section ${\sigma }_{\text {T}}$ of 0.25 ± 0.05 eV and $9.0\,\, {\pm } 1.0 {\times } 10^{-18}$ cm2, was verified to locate in the AlGaN buffer layer by I-DLTS. A combination of pulsed ${I}$ - ${V}$ and I-DLTS measurements, could be an effective method for in-situ study of current collapse mechanism in AlGaN/GaN HEMTs. [ABSTRACT FROM AUTHOR]

The impact of dynamic threshold voltage (${V}_{{\text {th}}}$) on the real-time characteristics of GaN direct-coupled FET logic (DCFL) inverter is investigated using an in-situ voltage tracking method. Due to the electrons’ trapping/de-trapping process at the gate dielectric/AlGaN-barrier interface, a two-step positive shift of the threshold input (${V}_{{\text {T}}}$) is observed in the device-under-test (DUT) inverter circuit, including the start-up periods and the self-adjusted dynamic equilibrium periods. The dependence of the dynamic ${V}_{{\text {T}}}$ upon different temperatures, input voltage magnitude, and operating frequency, is systematically studied and the underlying mechanism is revealed. Compared with the dc ${V}_{\text {T}}$ of the inverter of 3.6 V, the dynamic ${V}_{\text {T}}$ at 1 MHz switching with 8 V input amplitude shifts to ~5 V, which poses a challenge to GaN power integrated circuit (IC). [ABSTRACT FROM AUTHOR]

Plasma enhanced atomic layer deposition (PEALD) SiN gate dielectric is performed on AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistor (MIS-HEMT). The fabricated MIS-HEMTs with 5 nm SiN gate dielectric layer exhibits a tiny threshold voltage hysteresis (~ 0.04 V), sufficiently decreased leakage current of ~10−9 A/mm at ${V}_{\text {GS}} =-{60}$ V and good threshold voltage (${V}_{\text {TH}}$) stability even measured at 200 °C. The increased mobility of 2-D electron gas (2-DEG) and suppressed current collapse are demonstrated, thereby producing a power density of 7.05 W/mm with an associated 34.0 % power-added efficiency (PAE) and a peak PAE of 51.4 % in a continuous-wave mode at 30 GHz. [ABSTRACT FROM AUTHOR]

Integration of an enhancement-mode (E-mode) metal–insulator–semiconductor high-electron-mobility transistor (MIS-HEMT) with a high-performance lateral Schottky barrier controlled Schottky (LSBS) rectifier in a compact layout is fabricated on an ultrathin-barrier AlGaN/GaN heterostructure grown on Si substrate. The state-of-the-art reverse conduction voltage (Vrev) of 0.455 V was achieved in the monolithic integrated E-mode power device with a threshold voltage of 1.55 V. Vrev exhibited a tiny temperature variation of 0.66% from 0 °C to 150 °C compared with that of 157% for the controlled E-mode HEMT. [ABSTRACT FROM AUTHOR]

A Ka-band AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistor (MIS-HEMT) with SiN gate dielectric grown by plasma-enhanced atomic layer deposition (PEALD) is demonstrated. The gate reverse leakage current in a controlled HEMT is reduced by about three orders of magnitude by the PEALD-SiN, contributing to an improved breakdown voltage of 92.5 V (source–drain separation of 2.0~μm) in the fabricated MIS-HEMTs. The MIS-HEMTs also feature small threshold voltage hysteresis in dc transfer and capacitance–voltage characterizations, suggesting a good PEALD-SiN/AlGaN interface. The fabricated MIS-HEMTs deliver a high output power density of 7.16 W/mm and a peak power-added efficiency of 60.3%, respectively, at VDS = 30 V and VDS = 10 V in pulse mode at 28 GHz. PEALD-SiN could be a compelling gate dielectric for fabrication of high-power and high-efficiency MIS-HEMTs. [ABSTRACT FROM AUTHOR]

Low damage atomic layer etching (ALE) gate recess is developed for fabrication of millimeter-wave AlGaN/GaN high-electron-mobility transistors (HEMTs). Plasma ion induced bombardments to the AlGaN barrier is effectively suppressed by the ALE recess, contributing to a well-controlled recessed surface morphology. The suppressed lattice damage to AlGaN/GaN heterostructure is also reflected by a significantly reduced gate leakage as well as an invisible threshold voltage shift associated with damage induced traps. With a 0.15-μm T-gate fabrication technology, a high power-gain cutoff frequency fMAX of 205 GHz has been achieved. The ALE-recessed AlGaN/GaN HEMTs exhibits a record high power-added-efficiency (PAE) of 43.6% at 40 GHz in a continuous-wave mode. The associated gain and output power density are also remarkably improved compared with controlled HEMTs with conventional gate recess process. [ABSTRACT FROM AUTHOR]

In this letter, a high-temperature (HT) gate recess technique is implemented into the fabrication of high-performance millimeter-wave AlGaN/GaN high-electron-mobility transistors (HEMTs). By virtue of the low damage feature of the HT recess, a high extrinsic transconductance of 422 mS/mm, a three-terminal breakdown voltage of 134 V with a source–drain separation of 2.4 $\mu \text{m}$ , and a remarkable low Schottky gate leakage current of $1.6\times 10^{-6}$ A/mm at ${V}_{\textsf {GS}} = -\textsf {60}$ V are achieved, which is at least two orders of magnitude lower than the HEMTs with gate recessed at room temperature. By employing a 0.2- $\mu \text{m}$ T-shaped gate technology, a current-gain cutoff frequency ${f}_{T}$ of 81 GHz and a unit-power-gain frequency ${f}_{\textsf {MAX}}$ of 194 GHz are realized. The current collapse in the HT-recessed AlGaN/GaN HEMTs is significantly suppressed, contributing to a record high power-added-efficiency of 42.8%, as well as high output power density of 5.1 W/mm at 35 GHz in a continuous-wave mode. [ABSTRACT FROM AUTHOR]

(Al)GaN recess-free normally OFF technology is developed for fabrication of high-yield lateral GaN-based power devices. The recess-free process is achieved by an ultrathin-barrier (UTB) AlGaN/GaN heterostructure that features a natural pinched-off 2-D electron gas channel. The top–down manufacturing technique overcomes the challenges in etching of AlGaN barrier with well-controlled depth and uniformity, which is especially attractive for fabrication of normally OFF GaN-based high-electron-mobility transistors (HEMTs) and metal–insulator–semiconductor HEMTs (MIS-HEMTs) on large-size Si substrate. With SiNx passivation grown by low-pressure chemical-vapor deposition, on-resistance of the UTB-AlGaN/GaN-based power devices can be significantly reduced. High-uniformity low-hysteresis normally OFF HEMTs and Al2O3/AlGaN/GaN MIS-HEMTs are successfully demonstrated on the UTB AlGaN/GaN-on-Si platform. It is also a compelling technology platform for manufacturing high-performance GaN-based lateral power diodes, and normally OFF p-(Al)GaN heterojunction field-effect transistors. [ABSTRACT FROM PUBLISHER]

Ultra-thin-barrier (UTB) AlGaN/GaN heterostructure is utilized for fabrication of normally-OFF GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs). The sheet resistance of 2-D electron gas in the UTB Al0.22Ga0.78N(5-nm)/GaN heterostructure is effectively reduced by SiNx passivation grown by low-pressure chemical vapor deposition, from 2570 to 334~\Omega /□. The fabricated Al2O3/AlGaN/GaN MIS-HEMTs exhibit normally-OFF behavior with good V_{\mathrm {TH}} uniformity and low V_{\mathrm {TH}} -hysteresis. 20 mm-gate-width power devices featuring a low R\sc {\mathrm{ on}} of 0.75~\Omega ( \textI\mathrm {D,MAX} =6.5 A) are also demonstrated on the platform. [ABSTRACT FROM PUBLISHER]

The effects of GaN channel layer thickness on dc and RF performance of AlGaN/GaN high-electron mobility transistors (HEMTs) with a state-of-the-art composite AlGaN/GaN (1/1 \mum ) buffer were systematically investigated. Although HEMTs with a thick GaN channel layer exhibit slight degraded dc and RF small-signal performance associated with short-channel effects, they demonstrate significantly enhanced OFF-state breakdown voltage and RF large-signal performance. The 1-mm HEMTs with a 150-nm-thick GaN channel layer feature a 1.4 dB higher saturated POUT and about 10% higher PAE than that with a 50-nm-thick GaN channel layer, in both Classes AB and B operation conditions. Pulse I-V characterization reveals that the buffer-related current collapse is also suppressed in the thick GaN channel sample as compared with the thin one, suggesting that a thick GaN channel layer will not only reduces the deep traps in the channel, but also reduces the electron capture probability by deep traps in the composite AlGaN/GaN buffer. The selection of a proper GaN channel layer thickness is thus of great importance to the designation of GaN-based power amplifiers for various applications. [ABSTRACT FROM PUBLISHER]

In this letter, we report high-performance enhancement-mode (E-mode) Al2O3/AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) fabricated with high-temperature low-damage gate recess technique. The high-temperature gate recess is implemented by increasing the substrate temperature to 180 °C to enhance the desorption of chlorine-based etching residues during the dry etching of AlGaN barrier. High-crystal-quality Al2O3 gate dielectric was grown by atomic-layer deposition using O3 as the oxygen source to suppress hydrogen-induced weak bonds. The fabricated E-mode MIS-HEMTs exhibit a threshold voltage of 1.6 V, a pulsed drive current of 1.13 A/mm, and very low OFF-state standby power of 6.8 \times 10^\mathrm -8 W/mm at V\mathrm {GS} =0 V and V\mathrm {DS} =30 V. At 4 GHz and in pulse-mode operation, the output power density and power-added efficiency were measured to be 5.76 W/mm and 57%, both of which are the highest for GaN-based E-mode MIS-HEMTs reported to date. [ABSTRACT FROM AUTHOR]

Low-pressure chemical vapor deposition (LPCVD) technique is utilized for SiNx passivation of AlGaN/GaN high-electron-mobility transistors (HEMTs). A robust SiNx/ AlGaN interface featuring high thermal stability and well-ordered crystalline structure is achieved by a processing strategy of “passivation-prior-to-ohmic” in HEMTs fabrication. Effective suppression of surface-trap-induced current collapse and lateral interface leakage current are demonstrated in the LPCVD-SiNx passivated HEMTs, as compared with conventional plasma-enhanced chemical vapor deposition-SiNx passivated ones. Energy dispersive X-ray spectroscopy mapping analysis of SiNx/AlGaN interfaces suggests the interface traps are likely to stem from amorphous oxide/oxynitride interfacial layer. [ABSTRACT FROM AUTHOR]

This letter reports a 0.2-\mum gate AlGaN/GaN high-electron-mobility transistors (HEMTs) on an Si substrate passivated with an AlN/SiNx (4/20 nm) stack layer. The 4-nm-thick AlN was grown by plasma-enhanced atomic-layer-deposition. The AlN/SiNx-passivated HEMTs exhibit a high maximum drain current of 930 mA/mm, an three-terminal OFF-state breakdown voltage (BVDS) of 119 V, and a small threshold voltage shift of 130 mV in a wide drain bias range (VDS=3-24~V). Owing to the additional positive polarization charge in the AlN passivation layer, the access resistance Rs in the GaN-on-Si HEMTs is significantly reduced while maintaining small parasitic gate-drain capacitance Cgd, contributing to a high power-gain cutoff frequency fMAX of 182 GHz and a high Johnson's figure of merit of BVDS\times f\,T of 6.43\times 10^12~V/s simultaneously. The accuracy of the RF performance is verified by a small signal modeling based on measured S-parameters. [ABSTRACT FROM AUTHOR]