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GaN smart power chip technology has been realized using a GaN-on-Si HEMT platform, featuring monolithically integrated high-voltage power devices and low-voltage peripheral devices for mixed-signal functional blocks. In particular, this brief presents the imperative analog functional block-voltage reference generator for smart power applications with wide-temperature-range stability. The circuit is capable of proper functions within a wide temperature range from room temperature up to 250°C , illustrating the unique advantage of the wide-bandgap GaN in high-temperature operation. The voltage reference generator was designed with an AlGaN/GaN HEMT and Schottky diodes, and the devices were operated in the subthreshold regime to obtain low power consumption. The voltage reference generator achieved an average drift of less than 0.5 mV/°C and can be used as a reference voltage in various biasing and sensing circuits.

We report an in situ low-damage pre-gate treatment technology in an atomic layer deposition (ALD) system prior to the ALD- Al2O3 deposition, to realize high-quality Al2O3/III-nitride (III-N) interface. The technology effectively removes the poor quality native oxide on the III-N surface while forming an ultrathin monocrystal-like nitridation interlayer (NIL) between Al2O3 and III-N surface. With the pre-gate treatment technology, high-performance Al2O3(NIL)/GaN/AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors are demonstrated, exhibiting well-behaved electrical characteristics including suppressed gate leakage current, a small subthreshold slope of ~64 mV/dec, and a small hysteresis of ~0.09 V.

In this paper, a zero-bias mixer using a lateral field-effect diode fabricated on standard GaN-on-Si AlGaN/GaN high-electron-mobility-transistor wafers is demonstrated. The diode features strong nonlinearity near zero bias, enabled by a threshold-voltage modulation using a fluorine-plasma-treatment technique. The maximum change in conductance was adjusted to ~0 V, leading to optimal conversion loss (CL) of the mixer at zero bias and eliminating the need for any dc supplies. The mixer is characterized from room temperature (RT) to 250degC . At 2.5 GHz and at RT, the CL and third-order intermodulation intercept point are 12.9 dB and 17.64 dBm, respectively. The operation of the proposed diode is modeled by a physical equivalent circuit, with the element values extracted from the measured S-parameters. The voltage-biasing dependence of the CL can be explained by the model. The high-temperature operation of the mixer shows that the proposed mixer can perform well in high-temperature and ultralow-power applications.

CMOS-compatible 100/650 V enhancement-mode FETs and 650 V depletion-mode MISFETs are fabricated on 6-inch AlGaN/GaN-on-Si wafers. They show high breakdown voltage and low specific on-resistance with good wafer uniformity. The importance of epitaxial quality is figured out in a key industrial item: high-temperature-reverse-bias-stress-induced on-state drain curent degradation. Optimization of epitaxial layers shows significant improvement of device reliability.

In this paper, the reliable SiN x /AlGaN/GaN MISHEMTs on silicon substrate with improved trap-related characteristics have been well demonstrated. The devices with our proposed treatment method showed less deep-level traps and more Si surface donors at SiN x -AlGaN interface. The trap related device characteristics are also improved by using our optimized treatment method. The devices with proposed treatment method exhibit less current collapse and better positive bias temperature stability of threshold voltage. All the results suggest that the proposed treatment method is very effective to improve the slow-trap related device reliability.

CMOS-compatible GaN-on-silicon technology with excellent D-mode MISHFET performance is realized. A low specific contact resistance R c (0.35 Ω-mm) is achieved by Au-free process. MIS-HFET with a gate-drain distance (L GD ) of 15 μm exhibits a large breakdown voltage (BV) (980 V with grounded substrate) and a low specific on-resistance (R ON , sp ) (1.45 mΩ-cm 2 ). The importance of epitaxial quality in a key industrial qualification item: high temperature gate bias (HTGB) stress-induced voltage instability issue is figured out and a breakthrough by optimizing GaN epitaxial layer for improvement of MIS-HFET is demonstrated. A low V th shift of the optimized MIS-HFET is achieved ~ 0.14V with qualification stress condition V G of -15 V at ambient temperature of 150 oC for 128 hours.

An AlGaN/GaN HEMT-compatible lateral field-effect diode has been used for zero-bias microwave detector application. Using the versatile fluorine plasma ion treatment technique, we have been able to realize a diode that exhibits strong nonlinearity near zero bias, thus, eliminating DC supplies in microwave detector circuits. The AlGaN/GaN microwave detectors deliver high sensitivity, wide dynamic range and high temperature operating capability. The maximum zero-bias curvature coefficient (?) measured are 11.6 V -1 and 3.2 V -1 at 50°C and 250°C, respectively, yielding a directly-measured sensitivity (sv) of 1027 mV/mW at 50°C and 466 mV/mW at 250°C. The peak conjugately-matched sensitivity (sv,opt) is projected to be 9030 mV/mW at 2 GHz at 50°C. At room temperature, the wide dynamic range of 53 and 54 dB at 2 and 5 GHz are observed, respectively, both of which are the highest values reported so far.

With an in situ low-damage NH3-Ar-N2 plasma pre-gate treatment, a high-quality Al2O3/GaN-cap interface has been obtained in the Al2O3/GaN/AlGaN/GaN MIS-structures. Frequency- and temperature-dependent C-V characterization techniques were developed to map the interface trap density (Dit) at the dielectric/III-nitride interface, whereby a low Dit of ~1012-1013 cm-2eV-1 in the Al2O3/GaN/AlGaN/GaN MIS-structures was extracted. The mechanism for the high-quality interface was validated to be effective removal of native oxide and the subsequent formation of a monocrystal-like nitridation inter-layer on the GaN surface. Both Dit mapping and the pre-gate treatment techniques are of significance for the improvement of III-nitride MIS-HEMTs.

We demonstrate a single-chip switch-mode boost converter that features a monolithically integrated lateral field-effect rectifier (L-FER) and a normally off transistor switch. The circuit was fabricated on a standard AlGaN/GaN HEMT epitaxial wafer grown with GaN-on-Si technology. The fabricated rectifier with a drift length of 15 mum exhibits a breakdown voltage of 470 V, a turn-on voltage of 0.58 V, and a specific on-resistance of 2.04 mOmegaldrcm2. The L-FER exhibits no reverse recovery current associated with the turn-off transient because of its unipolar nature. A prototype of GaN-based boost converter that includes monolithically integrated rectifiers and transistors is demonstrated using conventional GaN-on-Si wafers for the first time to prove the feasibility of the GaN-based power IC technology.

A zero-bias microwave detector using AlGaN/GaN-based lateral field-effect diode is demonstrated. The diode is compatible with AlGaN/GaN HEMT in fabrication process. Taking advantage of threshold-voltage modulation of fluorine plasma treatment technique, the diode features low turn-on voltage and strong nonlinearity at zero bias thus eliminating DC supplies for the application of zero-bias microwave detection. The diode exhibits good sensitivity from room temperature to 250 °C. The peak on-wafer measured sensitivity (β v ) of 1027 mV/mW is achieved at 5 GHz at 50 °C. The maximum conjugately-matched sensitivity (β v,opt ) of 9030 mV/mW is obtained at 2 GHz at 50 °C and decreases to 1227 mV/mW at 250 °C. At room temperature, the dynamic range as high as 53 and 54 dB at 2 and 5 GHz is observed, respectively, which are the highest values reported so far.

GaN smart power chip technology has been realized using GaN-on-Si HEMT platform, featuring monolithically integrated high-voltage power devices and low-voltage peripheral devices for mixed-signal functional blocks. Two imperative functional blocks for smart power applications with wide-temperature-range stability are demonstrated. The first one is a voltage reference generator, and the second one is a temperature-compensated comparator. These circuits are capable of proper functions within a wide temperature range from room temperature up to 250 °C, illustrating the unique advantage of the wide-bandgap GaN. The voltage reference generator was designed with an AlGaN/GaN HEMT and Schottky diodes, and the devices were operated in the subthreshold regime to obtain low power consumption. The voltage reference generator achieved an average drift of less than 70 ppm/°C and can be used as a reference voltage in various biasing and sensing circuits. The temperature-dependent performance of a conventional comparator is characterized and a new temperature-compensated comparator circuit is proposed. The positive limiting level of the temperature-compensated comparator is less than 450 ppm/°C drift compared to 1350 ppm/°C in the conventional comparator.

A lateral field-effect rectifier (L-FER) that can be fabricated with normally-off transistor on the same AlGaN/GaN HEMT with the same fabrication process has been demonstrated. The L-FER exhibits low turn-on voltage, low specific on-resistance and high reverse breakdown. A prototype of switch-mode dc-dc boost converter that features monolithically integrated L-FER and normally-off HEMT is demonstrated for the first time using industry-standard GaNon-Si epitaxial wafers to prove the feasibility of GaN power integrated technology.

The lateral field effect rectifier (L-FER) on AlGaN/GaN heterostructure on silicon substrate compatible with the HEMT process has been characterized for high temperature operation (up to 250 degC). The proposed rectifier takes advantage of adjusting the forward-on voltage to a slightly positive value by fluorine plasma treatment. The temperature dependences of the forward-on voltage and the on-resistance of the rectifiers with different drift lengths were measured. The knee voltage of the rectifier exhibits very little temperature dependence as the temperature raised to 250 degC. These results indicate that L-FER is promising for operation over a wide range of ambient temperatures.

In conclusion, an AlGaN/GaN HEMT-compatible lateral field-effect rectifier is demonstrated by utilizing the threshold-voltage controlling capability of the fluorine plasma treatment technique. The rectifier features low on-resistance, low turn-on voltage, high temperature operation and high reverse breakdown voltage. The rectifier is expected to exhibit fast reverse recovery time because of its unipolar nature. In addition, the rectifiers are fabricated with the same process as the normally-off AlGaN/GaN HEMTs, indicating a robust low-cost approach of realizing GaN-based power integrated circuits.

Surface acoustic wave (SAW) devices using two-dimensional electron gas (2DEG) as interdigital transducers (IDTs) on AlGaN/GaN heterostructure has been demonstrated using a planar isolation technique based on the fluoride-based (CF4) plasma treatment technique. The RF characteristics of the SAW filters with planar 2DEG IDTs are compared with SAW devices that are made of metal IDTs or hybrid metal/2DEG IDTs.

Surface acoustic wave (SAW) filters using two-dimensional electron gas (2DEG) as interdigital transducers (IDT) on AlGaN/GaN heterostructure has been demonstrated for the first time using a fluoride-based (CF4) plasma treatment technique. The CF4 plasma treatment is used to pattern 2DEG IDT on a planar surface without removing the top AlGaN layer. The RF characteristics of the SAW filters with planar 2DEG IDTs are compared with metal IDT SAW filters. It is shown that the massloading effects and the triple-transit-interference (TTI) are suppressed in the 2DEG IDT SAW devices owing to the removal of the metal IDTs. It is capable of reducing not only the passband ripple, but also the size of devices because 2DEG IDTs can be placed closer. In addition, the detection part of the SAW sensor can be performed on the top of the planar 2DEG IDTs rather than in the SAW propagation path. This novel SAW device can be integrated with high-electron mobility transistors (HEMTs) on AlGaN/GaN heterostructure to deliver a viable approach for single chip GaN wireless sensors.

We demonstrate a new planar fabrication technology for integrating surface acoustic wave (SAW) filters with high-electron mobility transistors (HEMTs) on AlGaN/GaN heterostructures using fluoride-based (CF4) plasma treatment techniques. The CF4 plasma treatment has been shown capable of effectively depleting the two-dimensional electron gas (2DEG) without removing the top AlGaN layer. It is not only able to achieve the same level of active device isolation, but also able to permit the acousto-electric transductions in the interdigital transducers (IDTs) of the SAW filters. The RF characteristics of the planar SAW filter was similar to those of SAW filters directly fabricated on GaN layer exposed by using the mesa etching. Compared to the SAW device without HEMT, the integrated SAW/HEMT exhibited an insertion loss that was 5.129 dB lower because of the amplification by the output HEMT

This paper presents the dc and dynamic characterizations of a GaN-based voltage comparator, fabricated with monolithic integration of enhancement-mode (E-mode) and depletion-mode (D-mode) AlGaN/GaN high electron mobility transistors (HEMTs). The comparator features high gain (>31 dB) and wide bandwidth (>4 MHz), and small propagation delay time (

A high electron mobility transistor (HEMT)-compatible power lateral field-effect rectifier (L-FER) with low turn-on voltage is demonstrated using the same fabrication process as that for normally off AlGaN∕GaN HEMT, providing a low-cost solution for GaN power integrated circuits. The power rectifier features a Schottky-gate-controlled two-dimensional electron gas channel between the cathode and anode. By tying up the Schottky gate and anode together, the forward turn-on voltage of the rectifier is determined by the threshold voltage of the channel instead of the Schottky barrier. The L-FER with a drift length of 10μm features a forward turn-on voltage of 0.63V at a current density of 100A∕cm2. This device also exhibits a reverse breakdown voltage (BV) of 390V at a current level of 1mA∕mm and a specific on resistance (RON,sp) of 1.4mΩcm2, yielding a figure of merit (BV2∕RON,sp) of 108MW∕cm2. The excellent device performance, coupled with the lateral device structure and process compatibility with AlGaN∕GaN...

Surface acoustic wave (SAW) devices using two-dimensional electron gas (2DEG) as interdigital transducers (IDTs) on AlGaN∕GaN heterostructure has been demonstrated using a planar isolation technique based on the fluoride-based (CF4) plasma treatment technique. The rf characteristics of the SAW filters with planar 2DEG IDTs are compared with SAW devices that are made of metal IDTs or hybrid metal/2DEG IDTs.