PAM-XIAMEN offers GaN on SiC HEMT epitaxial wafer, which is HEMT stacks grown on semi insulation SiC for fabricating microwave RF devices, working on III-N material-growth and devices.
1. GaN on SiC HEMT Wafer for RF Application
No.1 GaN-on-SiC HEMT Epistructure
| Wafer size | 2”, 3”, 4”, 6” |
| AlGaN/GaN HEMT structure | Refer 1.2 |
| Carrier density | 6E12~2E13 cm2 |
| Hall mobility | 1300~2200 cm2v-1s-1 |
| XRD(102)FWHM | – |
| XRD(002)FWHM | – |
| Sheet Resistivity | 200~450 ohm/sq |
| AFM RMS (nm）of 5x5um2 | <0.25nm |
| Bow(um) | <=35um |
| Edge exclusion | <2mm |
| SiN passivation layer | 0~30nm |
| GaN cap layer | 2nm |
| Al composition | 20-30% |
| In composition | xx% for InAlN |
| AlGaN | / |
| AlN interlayer | / |
| GaN channel | / |
| Fe doped GaN buffer | 1.6um |
| AlN buffer layer | / |
| Substrate material | SiC Substrate |
The radial resistance distribution of GaN on SiC HEMT wafer is shown as figure:
Resistance on GaN / SiC Wafer Mapping
The RF GaN / SiC HEMT square resistance is detected as below:
Rs run2run —HEMT on SiC
No.2 GaN-on-SiC HEMT Structure without Back Barrier
PAM200808 – SICH
| Layer No. | Layer Name | Material | Thickness |
| 4 | Barrier layer | Al(0.23)Ga(0.77)N | – |
| 3 | Interlayer | AlN | ~1nm |
| 2 | Channel layer | GaN | – |
| 1 | RF buffer | – | |
| Substrate | 4inch SiC |
2. About the GaN on SiC HEMT Epitaxy
GaN on SiC HEMT technology combines the excellent thermal conductivity of SiC with the high power density and low loss capability of GaN. Compared with Si substrate, SiC substrate is a very dissipative material. The GaN on SiC thermal conductivity is high, so devices can operate under high voltage and high drain current, and the junction temperature will slowly increase with the RF power. Therefore, the RF performance is better on GaN on SiC HEMT, and the GaN on SiC epitaxy is a suitable material for RF applications.
Under the same dissipation conditions, the reliability and service life of devices fabricated on GaN epitaxial growth on SiC HEMT are better. In current GaN on SiC market, due to the limited size of SiC substrate, only 2”, 3”, 4”, 6” GaN-on-SiC HEMT wafers can be produced by GaN on SiC fab, and 8” wafers have not been promoted.
At present, this thin and light GaN-on-SiC solution is mainly used for radio frequency, and it will move towards power applications in the future. Because it can achieve higher power, compared with GaN-on-Si HEMT, it has stronger irreplaceability, especially in electric vehicle applications, the target voltage is generally 900 to 1200V. In this regard, GaN-on-SiC HEMT has more advantages, and the cost of the substrate will be reduced.
Silicon Carbide based Gallium Nitride has now been used in the fields of wireless infrastructure (4G/LTE base station), defense and communication satellites. In these areas, the highest performance and reliability must be available. Silicon Carbide based Gallium Nitride HEMT is also a strong competitor to 5G MIMO infrastructure. With the continuous advancement of Gan on SiC process, the GaN-on-SiC price will be more competitive with high quality.
3. FAQ about GaN based HEMT Wafer
Q1: Do you think SiN will help to protect the top layer and structure from getting contamination during shipping? If it protects the structure, then do deposit SiN.
A: Yes, SiN will help for protection, we will do deposit SiN.
Q2: What is the AlN nucleation layer thickness for GaN HEMT epi-structure on 6H, 4H, Si?
A: The thickness of AlN nucleation layer stack on GaN HEMT structure should be 100-150nm.
Q3：Do you have any information regarding the thermal budget of GaN/SiC wafers? Will they survive 800 ℃ in the nitrogen atmosphere for 2 hours? Are there any diffusion processes in epi-layers, which can change their properties?
A: 1/ Delta in GaN/SiC wafer <30deg.
2/ 800deg. is the critical temperature for GaN stability. The problem is not big in XX hours, and it is difficult to say for two hours, it is better to lower than xx deg. (please send email to tech@powerwaywafer.com for details)
3/ We have technology to prove that 800deg. will not cause performance degradation due to diffusion. (201127)
Q4: You mentioned a technology above to prove no performance degradation of GaN on SiC due to diffusion. I wonder what it means, what is this technology?
A: In our own Fab wafers, there is a step of passivation layer deposition in GaN/SiC wafer, and the process temperature is about XX ℃. The outflow HEMT device can maintain good Ron, IDS, breakdown performance. (please send email to tech@powerwaywafer.com for details)
Q5: We are interested to fabricate a HEMT at 4GHz and 8GHz. Can we use your HEMT Wafer to fabricate HEMT at these frequencies?
Please provide me quotation of the GaN HEMT wafers.
A: If you use it for 4GHz and 8GHz, we suggest you use GaN HEMT structure on silicon carbide, also it should be RF structure. For detailed structure please refer to the above specification listed.
Q6: Can you, please, elaborate the spec for GaN grown on prime SiC A grade and B grade?
A: 1) It looks similar, but for commercial bulk order from industry, they use GaN on SiC A grade, while GaN on B grade are used in high research grade.
2) for GaN/SiC epi wafer itself, you will find defects is much lower than what you order before.Of course, on A grade it is the best.
3) for yield rate on chip fabrication, GaN on A grade SiC is much higher a lot.
For more information, please contact us email at victorchan@powerwaywafer.com and powerwaymaterial@gmail.com.