| 1. |
|
|
| 2. |
- Bergsten, Johan, 1988, et al.
(författare)
-
Electron Trapping in Extended Defects in Microwave AlGaN/GaN HEMTs with Carbon-Doped Buffers
- 2018
-
Ingår i: IEEE Transactions on Electron Devices. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1557-9646 .- 0018-9383. ; 65:6, s. 2446-2453
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates AlGaN/GaN high-electron mobility transistors (HEMTs) fabricated on epistructures with carbon (C)-doped buffers. Metalorganic chemical vapor deposition is used to grow two C-doped structures with different doping profiles, using growth parameters to change the C incorporation. The C concentration is low enough to result in n-type GaN. Reference devices are also fabricated on a structure using iron (Fe) as dopant, to exclude any process related variations and provide a relevant benchmark. All devices exhibit similar dc performance. However, pulsed I - V$ measurements show extensive dispersion in the C-doped devices, with values of dynamic R-mathrm-scriptscriptstyle ON 3 -4 times larger than in the dc case. Due to the extensive trapping, the devices with C-doped buffers can only supply about half the output power of the Fe-doped sample, 2.5 W/mm compared to 4.8 W/mm at 10 GHz. In drain current transient measurements, the trap filling time is varied, finding large prevalence of trapping at dislocations for the C-doped samples. Clusters of C around the dislocations are suggested to be the main cause for the increased dispersion.
|
|
| 3. |
- Chen, Ding Yuan, et al.
(författare)
-
Microwave Performance of 'Buffer-Free' GaN-on-SiC High Electron Mobility Transistors
- 2020
-
Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 41:6, s. 828-831
-
Tidskriftsartikel (refereegranskat)abstract
- High performance microwave GaN-on-SiC HEMTs are demonstrated on a heterostructure without a conventional thick doped buffer. The HEMT is fabricated on a high-quality 0.25~\boldsymbol {\mu }\text{m} unintentional doped GaN layer grown directly on a transmorphic epitaxially grown AlN nucleation layer. This approach allows the AlN-nucleation layer to act as a back-barrier, limiting short channel effects and removing buffer leakage. The devices with the 'buffer-free' heterostructure show competitive DC and RF characteristics, as benchmarked against the devices made on a commercial Fe-doped epi-wafer. Peak transconductances of 500 mS/mm and a maximum saturated drain current of 1 A/mm are obtained. An extrinsic \text{f}-{\sf T} of 70 GHz and \text{f}-{\sf max} of 130 GHz are achieved for transistors with a gate length of 100 nm. Pulsed-IV measurements reveal a lower current slump and a smaller knee walkout. The dynamic IV performance translates to an output power of 4.1 W/mm, as measured with active load-pull at 3 GHz. These devices suggest that the 'buffer-free' concept may offer an alternative route for high frequency GaN HEMTs with less electron trapping effects.
|
|
| 4. |
- Chen, J. T., et al.
(författare)
-
A GaN-SiC hybrid material for high-frequency and power electronics
- 2018
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 113:4
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that 3.5% in-plane lattice mismatch between GaN (0001) epitaxial layers and SiC (0001) substrates can be accommodated without triggering extended defects over large areas using a grain-boundary-free AlN nucleation layer (NL). Defect formation in the initial epitaxial growth phase is thus significantly alleviated, confirmed by various characterization techniques. As a result, a high-quality 0.2-μm thin GaN layer can be grown on the AlN NL and directly serve as a channel layer in power devices, like high electron mobility transistors (HEMTs). The channel electrons exhibit a state-of-the-art mobility of >2000 cm2/V-s, in the AlGaN/GaN heterostructures without a conventional thick C- or Fe-doped buffer layer. The highly scaled transistor processed on the heterostructure with a nearly perfect GaN-SiC interface shows excellent DC and microwave performances. A peak RF power density of 5.8 W/mm was obtained at VDSQ= 40 V and a fundamental frequency of 30 GHz. Moreover, an unpassivated 0.2-μm GaN/AlN/SiC stack shows lateral and vertical breakdowns at 1.5 kV. Perfecting the GaN-SiC interface enables a GaN-SiC hybrid material that combines the high-electron-velocity thin GaN with the high-breakdown bulk SiC, which promises further advances in a wide spectrum of high-frequency and power electronics.
|
|
| 5. |
- Chen, J. T., et al.
(författare)
-
Carbon-doped GaN on SiC materials for low-memory-effect devices
- 2016
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781607685395 ; 75:12, s. 61-65, s. 61-65
-
Konferensbidrag (refereegranskat)abstract
- AlGaN/GaN on SiC HEMT structures suitable for high power, high frequency applications are demonstrated. The material manifests record breaking thermal management and electron mobility. Moreover, thanks to the fact that the buffer layer is doped with carbon, the memory effect of processed devices is very low making system design and manufacturing significantly easier and less expensive.
|
|
| 6. |
- Ding Yuan, Chen, 1991, et al.
(författare)
-
Impact of in situ NH3 pre-treatment of LPCVD SiN passivation on GaN HEMT performance
- 2022
-
Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 1361-6641 .- 0268-1242. ; 37:3
-
Tidskriftsartikel (refereegranskat)abstract
- The impact on the performance of GaN high electron mobility transistors (HEMTs) of in situ ammonia (NH3) pre-treatment prior to the deposition of silicon nitride (SiN) passivation with low-pressure chemical vapor deposition (LPCVD ) is investigated. Three different NH3 pre-treatment durations (0, 3, and 10 min) were compared in terms of interface properties and device performance. A reduction of oxygen (O) at the interface between SiN and epi-structure is detected by scanning transmission electron microscopy (STEM )-electron energy loss spectroscopy (EELS) measurements in the sample subjected to 10 min of pre-treatment. The samples subjected to NH3 pre-treatment show a reduced surface-related current dispersion of 9% (compared to 16% for the untreated sample), which is attributed to the reduction of O at the SiN/epi interface. Furthermore, NH3 pre-treatment for 10 min significantly improves the current dispersion uniformity from 14.5% to 1.9%. The reduced trapping effects result in a high output power of 3.4 W mm(-1) at 3 GHz (compared to 2.6 W mm(-1) for the untreated sample). These results demonstrate that the in situ NH3 pre-treatment before LPCVD of SiN passivation is critical and can effectively improves the large-signal microwave performance of GaN HEMTs.
|
|
| 7. |
- Ding Yuan, Chen, 1991, et al.
(författare)
-
Thin Al 0.5 Ga 0.5 N/GaN HEMTs on QuanFINE ® Structure
- 2021
-
Ingår i: CS MANTECH 2021 - 2021 International Conference on Compound Semiconductor Manufacturing Technology, Digest of Papers. ; , s. 153-155
-
Konferensbidrag (refereegranskat)abstract
- The performance of HEMTs fabricated on a thin Al0.5Ga0.5N/GaN heterostructure with a total barrier thickness of 6.5 nm is presented and benchmarked to the epi-structure with a 13 nm thick Al0.3Ga0.7N barrier on an identical QuanFINE® structure. DC transfer characteristics on both samples with a gate length of 100 nm demonstrate a high current above 1 A/mm. A higher extrinsic gm of 550 mS/mm is measured on the sample with a thinner high Al content barrier. Moreover, low trapping effects with a 12-14 % buffer-related dispersion at a VDSQ of 25 V are characterized for both samples, which indicate the advantage of the iron-free QuanFINE® heterostructure.
|
|
| 8. |
- Gogova, Daniela, et al.
(författare)
-
Epitaxial growth of β -Ga 2 O 3 by hot-wall MOCVD
- 2022
-
Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 12:5, s. 055022-055022
-
Tidskriftsartikel (refereegranskat)abstract
- The hot-wall metalorganic chemical vapor deposition (MOCVD) concept, previously shown to enable superior material quality and highperformance devices based on wide bandgap semiconductors, such as Ga(Al)N and SiC, has been applied to the epitaxial growth ofβ-Ga2O3. Epitaxial β-Ga2O3 layers at high growth rates (above 1 μm/h), at low reagent flows, and at reduced growth temperatures(740 ○C) are demonstrated. A high crystalline quality epitaxial material on a c-plane sapphire substrate is attained as corroborated by a combination of x-ray diffraction, high-resolution scanning transmission electron microscopy, and spectroscopic ellipsometry measurements. Thehot-wall MOCVD process is transferred to homoepitaxy, and single-crystalline homoepitaxial β-Ga2O3 layers are demonstrated with a 201 ¯rocking curve width of 118 arc sec, which is comparable to those of the edge-defined film-fed grown (201) ¯ β-Ga2O3 substrates, indicative ofsimilar dislocation densities for epilayers and substrates. Hence, hot-wall MOCVD is proposed as a prospective growth method to be furtherexplored for the fabrication of β-Ga2O3
|
|
| 9. |
|
|
| 10. |
|
|
