GaN-Based Trench Gate Metal Oxide Semiconductor Field-Effect Transistor Fabricated with Novel Wet Etching
TL;DR: In this article, a novel method for fabricating trench structures on GaN was developed and a smooth non-polar (1100) plane was obtained by wet etching using tetramethylammonium hydroxide (TMAH) as the etchant.
Abstract: A novel method for fabricating trench structures on GaN was developed. A smooth non-polar (1100) plane was obtained by wet etching using tetramethylammonium hydroxide (TMAH) as the etchant. A U-shape trench with the (1100) plane side walls was formed with dry etching and the TMAH wet etching. A U-shape trench gate metal oxide semiconductor field-effect transistor (MOSFET) was also fabricated using the novel etching technology. This device has the excellent normally-off operation of drain current–gate voltage characteristics with the threshold voltage of 10 V. The drain breakdown voltage of 180 V was obtained. The results indicate that the trench gate structure can be applied to GaN-based transistors.
Citations
More filters
20 May 2010
TL;DR: In this article, GaN power transistors on Si substrates for power switching application are reported, and current collapse phenomena are discussed for GaN-HFETs on Si substrate, resulting in suppression of the current collapse due to using the conducting Si substrate.
Abstract: In this paper, GaN power transistors on Si substrates for power switching application are reported. GaN heterojunction field-effect transistor (HFET) structure on Si is an important configuration in order to realize a low loss and high power devices as well as one of the cost-effective solutions. Current collapse phenomena are discussed for GaN-HFETs on Si substrate, resulting in suppression of the current collapse due to using the conducting Si substrate. Furthermore, attempts for normally off GaN-FETs were examined. A hybrid metal-oxide-semiconductor HFET structure is a promising candidate for obtaining devices with a lower on-resistance (Ron) and a high breakdown voltage (Vb).
454 citations
01 Jan 2010
TL;DR: A hybrid metal-oxide-semiconductor HFET structure is a promising candidate for obtaining devices with a lower on-resistance and a high breakdown voltage as well as one of the cost-effective solutions.
Abstract: In this paper, GaN power transistors on Si substrates for power switching application are reported. GaN heterojunction field-effect transistor (HFET) structure on Si is an important configuration in order to realize a low loss and high power devices as well as one of the cost-effective solutions. Current collapse phenomena are discussed for GaN-HFETs on Si substrate, resulting in suppression of the current collapse due to using the conducting Si substrate. Furthermore, attempts for normally off GaN-FETs were exam- ined. A hybrid metal-oxide-semiconductor HFET structure is a promising candidate for obtaining devices with a lower on-resistance ðRonÞ and a high breakdown voltage ðVbÞ.
448 citations
TL;DR: In this article, the GaN-based recessed MIS-gate structure in conjunction with negative polarization charges under the gate allows the high threshold voltage, whereas the low on-state resistance is maintained by the 2D electron gas remaining in the channel except for the recessed gate region.
Abstract: This letter reports normally-off operation of an AlGaN/GaN recessed MIS-gate heterostructure field-effect transistor with a high threshold voltage. The GaN-based recessed MIS-gate structure in conjunction with negative polarization charges under the gate allows us to achieve the high threshold voltage, whereas the low on-state resistance is maintained by the 2-D electron gas remaining in the channel except for the recessed MIS-gate region. The fabricated device exhibits a threshold voltage as high as 5.2 V with a maximum field-effect mobility of 120 cm2/Vmiddots, a maximum drain current of over 200 mA/mm, and a breakdown voltage of 400 V.
383 citations
Cites background from "GaN-Based Trench Gate Metal Oxide S..."
...Consequently, the GaN-based MIS-gate structure allows us to attain a positive threshold voltage like that of GaN MISFETs [17]–[20]....
[...]
...The maximum field-effect mobility is 120 cm2/V · s, which is comparable with those of previously reported GaN MISFETs [19], [20], [23]....
[...]
...In addition, owing to the 2DEG remaining in the channel except for the recessed MIS-gate region, lower ON-state resistance can be attained compared to the conventional GaN MISFETs [17]–[20]....
[...]
...In contrast, GaN-based MISFETs exhibited normally-off operation with a threshold voltage higher than 3 V [17]–[20]....
[...]
...itive threshold voltage like that of GaN MISFETs [17]–[20]....
[...]
TL;DR: In this paper, a redesigned epitaxial layer structure with a regular hexagonal trench gate layout was proposed to reduce the specific on-resistance to as low as 1.8 mΩcm2 while obtaining a sufficient blocking voltage for 1.2kV-class operation.
Abstract: In this paper, we report on 1.2-kV-class vertical GaN-based trench metal–oxide–semiconductor field-effect transistors (MOSFETs) on a free-standing GaN substrate with a low specific on-resistance. A redesigned epitaxial layer structure following our previous work with a regular hexagonal trench gate layout enables us to reduce the specific on-resistance to as low as 1.8 mΩcm2 while obtaining a sufficient blocking voltage for 1.2-kV-class operation. Normally-off operation with a threshold voltage of 3.5 V is also demonstrated. To the best of our knowledge, this is the first report on vertical GaN-based MOSFETs with a specific on-resistance of less than 2 mΩcm2.
258 citations
TL;DR: In this article, a lateral GaN power device with a blocking voltage of 600 V and a vertical GaN Power Switching Device with a block voltage of 1200 V are proposed for medium power applications for sub-systems and high-power applications for the drive of main motors, respectively.
Abstract: Many power switching devices are used in hybrid vehicles (HVs) and electric vehicles (EVs). To improve the efficiency of HVs and EVs, better performance characteristics than those of Si power devices, for example, lower on-resistance, higher speed, higher operation temperature, are required for the power devices. GaN power devices are promising candidates for satisfying the requirements. A lateral GaN power device with a blocking voltage of 600 V and a vertical GaN power device with a blocking voltage of 1200 V are suitable for medium power applications for sub systems and high-power applications for the drive of main motors, respectively. Power device applications in HVs and EVs and the current status of the GaN power device are presented. The reliability of the GaN power device is also discussed.
253 citations
References
More filters
TL;DR: In this paper, a novel approach was proposed to fabricate high-performance enhancement mode (E-mode) AlGaN/GaN HEMTs based on fluoride-based plasma treatment of the gate region.
Abstract: We report a novel approach in fabricating high-performance enhancement mode (E-mode) AlGaN/GaN HEMTs. The fabrication technique is based on fluoride-based plasma treatment of the gate region in AlGaN/GaN HEMTs and post-gate rapid thermal annealing with an annealing temperature lower than 500/spl deg/C. Starting with a conventional depletion-mode HEMT sample, we found that fluoride-based plasma treatment can effectively shift the threshold voltage from -4.0 to 0.9 V. Most importantly, a zero transconductance (g/sub m/) was obtained at V/sub gs/=0 V, demonstrating for the first time true E-mode operation in an AlGaN/GaN HEMT. At V/sub gs/=0 V, the off-state drain leakage current is 28 /spl mu/A/mm at a drain-source bias of 6 V. The fabricated E-mode AlGaN/GaN HEMTs with 1 /spl mu/m-long gate exhibit a maximum drain current density of 310 mA/mm, a peak g/sub m/ of 148 mS/mm, a current gain cutoff frequency f/sub T/ of 10.1 GHz and a maximum oscillation frequency f/sub max/ of 34.3 GHz.
629 citations
TL;DR: In this paper, an enhancement-mode high electron mobility transistors (E-HEMTs) on GaN/AlGaN heterostructures grown on SiC substrates are reported.
Abstract: Fabrication of enhancement-mode high electron mobility transistors (E-HEMTs) on GaN/AlGaN heterostructures grown on SiC substrates is reported. Enhancement-mode operation was achieved with high threshold voltage (V/sub T/) through the combination of low-damage and controllable dry gate-recessing and the annealing of the Ni/Au gates. As-recessed E-HEMTs with 1.0 /spl mu/m gates exhibited a threshold voltage (V/sub T/) of 0.35 V, maximum drain current (I/sub D,max/) of 505 mA/mm, and maximum transconductance (g/sub m,max/) of 345 mS/mm; the corresponding post-gate anneal characteristics were 0.47 V, 455 mA/mm and 310 mS/mm, respectively. The RF performance is unaffected by the post-gate anneal process with a unity current gain cutoff frequency (f/sub T/) of 10 GHz.
272 citations
TL;DR: In this paper, a self-aligned GaN MOSFET was fabricated using low-pressure chemical vapor-deposited silicon dioxide as gate dielectric and polysilicon as the gate material, with implant activation at 1100/spl deg/C for 5 min in nitrogen.
Abstract: Gallium nitride self-aligned MOSFETs were fabricated using low-pressure chemical vapor-deposited silicon dioxide as the gate dielectric and polysilicon as the gate material. Silicon was implanted into an unintentionally doped GaN layer using the polysilicon gate to define the source and drain regions, with implant activation at 1100/spl deg/C for 5 min in nitrogen. The GaN MOSFETs have a low gate leakage current of less than 50 pA for circular devices with W/L=800/128 /spl mu/m. Devices are normally off with a threshold voltage of +2.7 V and a field-effect mobility of 45 cm/sup 2//Vs at room temperature. The minimum on-resistance measured is 1.9 m/spl Omega//spl middot/cm/sup 2/ with a gate voltage of 34 V (W/L=800/2 /spl mu/m). High-voltage lateral devices had a breakdown voltage of 700 V with gate-drain spacing of 9 /spl mu/m (80 V//spl mu/m), showing the feasibility of self-aligned GaN MOSFETs for high-voltage integrated circuits.
165 citations
TL;DR: In this article, an enhancement-mode metal oxide semiconductor field effect transistors (MOSFETs) with trench gate structures have been developed for vertical switching devices with high breakdown voltage and highly integrated low on-resistance with the usage of excellent physical parameters of GaN.
Abstract: Enhancement-mode metal oxide semiconductor field effect transistors (MOSFETs) with trench gate structures have been developed. These MOSFETs show excellent DC characteristics with on-voltage of 5.1 V, i.e., enhancement-mode operation and extremely high channel mobilities of 133 cm2/(V s). This structure enables us to realize vertical switching devices with high breakdown voltage and highly integrated low on-resistance with the usage of excellent physical parameters of GaN. This excellent performance of these devices breaks though the realization of GaN-based power switching transistors.
77 citations
TL;DR: In this article, a combination of reactive ion etching and KOH wet etching was used to construct GaN striped structures along the and directions by a combination etching technique.
Abstract: GaN striped structures along the and directions were fabricated by a combination etching technique, consisting of reactive ion etching followed by KOH wet etching. After wet etching, the sidewalls of the striped structures along the direction became very smooth and straight, compared with normal wet etching and dry etching. From the differences of the etching along the direction, it was found that etching mainly occurs in the (1 100) plane. This phenomenon can be explained by the action of OH- ions, which are repelled by N dangling bonds on the surface and which attack Ga back bonds as well as the mechanism of (000 1) polar GaN etching.
42 citations