A survey of Gallium Nitride HEMT for RF and high power applications

We report a high-performance normally-off Al2O3/AlN/GaN MOS-channel-high electron mobility transistor (MOSC-HEMT) featuring a monocrystalline AlN interfacial layer inserted between the amorphous Al2O3 gate dielectric and the GaN channel. The AlN interfacial layer effectively blocks oxygen from the GaN surface and prevents the formation of detrimental Ga-O bonds. Frequency-dispersion in C-V characteristics and threshold voltage hysteresis are effectively suppressed, owing to improved interface quality. The new MOSC-HEMTs exhibit a maximum drain current of 660 mA/mm, a field-effect mobility of 165 cm2/V·s, a high on/off drain current ratio of ~1010, and low dynamic on-resistance degradation.

Interface Characterization of Normally-Off Al2O3/AlN/GaN MOS-Channel-HEMTs with an AlN Interfacial Layer

In this paper, we investigated characteristics of AlGaN/GaN high-electron mobility transistors (HEMTs) with high resistive buffer structure consisted of periodically carbon-doped (PCD) GaN buffer layer and AlGaN back barrier layer. The PCD structure was proposed for reducing undesirable trapping effects, which resulted in effective suppression of the current collapse compared to that in conventional carbon buffer structure. To further improve the dynamic performances of the device and to increase the electron confinement of the 2-D electron gas (2-DEG) channel, AlGaN back barrier was inserted between the GaN channel and the PCD buffer layer, which results in greatly improved current collapse with slightly improved 2-DEG mobility compared to those of the device without back barrier. The OFF-state leakage current of the device with back-barrier is about 2 orders lower in magnitude than that of device without back barrier, which leads to the breakdown voltage of 2 kV and figure of merit of 2.27 GV $^{2} \Omega ^{-1}$ cm−2 for the device with LGD of $10~{{\mu }}\text{m}$ , one of the highest values ever reported for the GaN-based HEMTs.

High Figure-of-Merit ( ${V}_{\text{BR}}^{\text{2}}$ / ${R}_{\text{ON}}$ ) AlGaN/GaN Power HEMT With Periodically C-Doped GaN Buffer and AlGaN Back Barrier

This work presents the effect of Al mole fraction and gate oxide on the direct current and low frequency noise characterization of GaN/AlGaN high electron mobility transistor (HEMT). Metal–oxide–semiconductor (MOS)-HEMT with SiO2 in the gate stack improved the Id(on)/Id(off) ratio up to more than 8 orders, compared to fabricated HEMT without oxide. It was shown that the gate leakage and isolation leakage suppression efficiency improved dramatically with the gate oxide. Subthreshold swing of MOS-HEMTs with different Al mole fractions (from 20% to 35%) varies slightly from 72 mV/decade to 79 mV/decade. Low frequency noise study revealed the difference in transport mechanism between HEMT and MOS-HEMTs. By using carrier number fluctuation model on the measured data, it was found that the noise is predominantly coming from the surface states. While generation-recombination is very prominent in HEMT, it is very insignificant in both MOS-HEMTs at much higher frequencies. This study reveals that very high number ...

Fabrication and comparative study of DC and low frequency noise characterization of GaN/AlGaN based MOS-HEMT and HEMT

Micro/nanowire-based devices have been envisioned as a promising new route toward improved electronic and optoelectronic applications, which attracts considerable research interests. However, suffering from applicable strategies to synthesize uniform core-shell structures to meet the requirement for the investigations of electrical transport behaviors along the length direction or high electron mobility transistor (HEMT) devices, heterojunction wire-based electronics have been explored limitedly. In the present work, GaN/AlN/AlGaN core-shell heterojunction microwires on patterned Si substrates were synthesized without any catalyst via metalorganic chemical vapor deposition. The as-synthesized microwires had low dislocation, sharp, and uniform heterojunction interfaces. Electrical transport performances were evaluated by fabricating HEMTs on the heterojunction microwire channels. Results demonstrated that a normally off operation was achieved with a threshold voltage of 1.4 V, a high on/off current ratio of 108, a transconductance of 165 mS/mm, and a low subthreshold swing of 81 mV/dec. The normally off operation may attribute to the weak polarization along semipolar facets of the heterojunction, which leads to weak constrain of 2DEG.

a-Axis GaN/AlN/AlGaN Core–Shell Heterojunction Microwires as Normally Off High Electron Mobility Transistors

This paper presents two structures of wide band gap high electron mobility transistor (HEMT). One structure is made-up of a stack of AlGaN layer over GaN layer. This structure is characterized by two-dimensional (2-D) electron gas layer formed at the interface of the AlGaN and GaN layers. The 2-D electron gas plays an important role in determining the carrier-mobility $$(\upmu )$$(μ) and hence drain-to-source current $$(I_\mathrm{DS})$$(IDS) of HEMT. The other structure introduces an AlN spacer layer between the AlGaN and GaN layers to improve these characteristics. This paper compares the output characteristics curves $$(I_\mathrm{DS}-V_\mathrm{DS})$$(IDS-VDS) and transconductance characteristics curves $$(I_\mathrm{DS}-V_\mathrm{GS})$$(IDS-VGS) obtained from simulations performed using Silvaco $$\hbox {ATLAS}^\mathrm{TM}$$ATLASTM. The modified structure with spacer layer shows improvements in carrier-mobility and hence drain-to-source current. This paper estimates and compares the subthreshold slope (SS) of the two devices. AlGaN/AlN/GaN HEMT offers an SS of 80 mV/decade whereas AlGaN/GaN HEMT offers an SS of 95 mV/decade. Thus, an improvement in SS of about 18.75 % is achieved in AlGaN/AlN/GaN HEMT compared to AlGaN/GaN HEMT. HEMT with spacer layer also offers 10$$\times $$× improvement in $$I_{DS}$$IDS as compared to HEMT without spacer layer. The proposed HEMTs achieve $$\approx $$?3.19$$\times $$× improvement in breakdown voltage, $$>$$>1.3$$\times $$× improvement in SS compared to HEMTs previously proposed in the literature.

Characterization of AlGaN/GaN and AlGaN/AlN/GaN HEMTs in terms of mobility and subthreshold slope

This paper characterizes a high electron mobility transistor (HEMT) having an undoped AlN spacer layer in the interface of AlGaN and GaN layers Two-dimensional (2-D) electron gas layer at the interface plays an important role in defining the mobility of charge carriers and hence drain current of HEMT Introduction of an AlN spacer layer between the AlGaN and GaN layers further causes an improvement in these characteristics The output characteristics curve (IDS-VDS) and transconductance curves (IDS-VGS) are analyzed by simulating the structure using Silvaco Atlas The proposed HEMT offers a sub threshold slope of 80 mV/decade and it is 153× lower than that of similar structure already reported in the literature

Characterization of AlGaN and GaN Based HEMT with AlN Interfacial Spacer

Since embedded systems have such a wide range of applications in today’s time, there is a pressing need to meet the design requirements such as power consumption, cost, time to market, flexibility and robustness. Power consumption by embedded systems is a particularly critical issue. This paper is a starting point for understanding power aware design methodologies, and it reviews the various techniques of designing power efficient embedded systems using Programmable System on Chip (PSoC). PSoC is a true programmable embedded SoC (System on Chip) which integrates configurable analog and digital components, memory and a microcontroller on a single chip thus providing high level of flexibility and configurability.

A Study on Power Optimization Techniques in PSoC

A structure of AlGaN/AlN/GaN High Electron Mobility Transistor with surface passivation is proposed in this paper. AlN layer in the proposed structure acts as spacer layer in order to improve the Two Dimensional electron gas mobility formed at the AlN/GaN junction. Output characteristics (Id-Vds), transfer characteristics (Id-Vgs), subthreshold slope and unity gain cut-off frequency (f T ) of the device are observed. The proposed device shows negligible leakage current in OFF state at V ds = 1 V. The device achieves maximum drain current of about 450 mA and exhibits a very steep and nearly ideal subthreshold slope of 63.3 mV/dec and hence can be used where very high speed transition between ON and OFF states is required. The simulated device exhibits unity current gain cutoff frequency (f T ) of 1 GHz. All the simulations are performed using Silvaco ATLASTM.

Development of HEMT device with surface passivation for a low leakage current and steep subthreshold slope

This paper proposes a High Electron Mobility Transistor (HEMT) which analyzed using Silvaco ATLASTM Tools. The proposed device is an AlGaN/GaN HEMT with AlN acting as a spacer layer. The design also includes a field plated gate to increase the breakdown voltage (F br ). The proposed device has a low threshold voltage V t =−11 V and minimal OFF state leakage current. The device exhibits peak drain current of 2.5 mA when the gate is biased at V gs = 1 V. The subthreshold slope is observed as 75 mV/dec and the ON-OFF current ratio observed is 1014. The proposed device achieves breakdown voltage in the range of 231 to 235 volts depending upon thickness of Gallium Nitride channel layer and hence the device can find high power applications.

Santashraya Prasad

Papers

Characterization of AlGaN/GaN and AlGaN/AlN/GaN HEMTs in terms of mobility and subthreshold slope

Characterization of AlGaN and GaN Based HEMT with AlN Interfacial Spacer

A Study on Power Optimization Techniques in PSoC

Development of HEMT device with surface passivation for a low leakage current and steep subthreshold slope

Analysis of breakdown voltage of a field plated High Electron Mobility Transistor