1. InAs Inserted HEMT
연성진

2. contents 1.Introduction 2.Structure & Device performance
3.Improvement scheme

3. InGaAs/InAlAs HEMT low noise and high frequency device
Conduction Band
2DEG
Fermi Level
Energy band diagram of a HEMT
low noise and high frequency device
high electron mobility & high sheet carrier density
high saturation drift velocity
Material
Bandgap
Energy (eV)
Electron Mobility
(cm2/V·s)
Peak Velocity
(cm/s) Si
1.13
1,300
1.0x107 Ge
0.76
3,800 -
GaAs
1.42
8,500
2.0x107
InP
1.26
4,600
2.7x107
InAs
0.35
27,000
4.2x107
In0.53GaAs
0.75
12,000
2.9x107

4. Channel structure Lower band gap material as channel material:
InGaAs channel
InAs channel
Lower band gap material as channel material:
Higher Electron confinement
Higher mobility
Lower noise
Lower sheet resistance
higher saturation drift velocity

5. InAs inserted HEMT For Higher gain Higher frequency characteristics
Cap InGaAs
Cap InGaAs
Barrier InAlAs
Barrier InAlAs
Channel InGaAs
Channel InGaAs
SubChannel InAs
Channel InGaAs
Buffer InAlAs
Buffer InAlAs
Substrate InP
Substrate InP
InGaAs/InAlAs HEMT
InAs Inserted HEMT
For
Higher gain
Higher frequency characteristics

6. Channel engineering Channel total thickness: 300Å
Target: Higher mobility
Variable: InAs thickness, Upper InGaAs thickness
Dependence on growth tech.

7. Device performance 0.1um T-Gate fT=290GHz @ Vds=0.5V
Low drain bias voltage limitation owing to the increased output conductance

8. Low drain bias voltage limitation
Low on-state breakdown
Bias sweep limitation
Drastic increment of output conductance
Low Fmax
By Impact ionization!

9. Impact Ionization process
Hole accumulation
1. Impact Ionization
2. Electron-hole pair is generated
3. the hole is attracted to source region
4. hole accumulation in source region
5. electron is attracted from source
by accumulated hole
Carrier multiplication
Positive
Feedback

10. Lowering Impact Ionization rate
Composite channel with low I.I threshold energy material
Channel quantization

11. Composite channel (with low I.I threshold energy material )
Impact ionization threshold energy in InP is higher than in InGaAs or InAs
wider band gap energy
larger electron effective mass.
=> contribute to decreased impact ionization effects

12. InGaAs/InP composite channel HEMT
Advantage of composite channel with InP:
InGaAs or InAs (high mobility at low fields)
InP (low impact- ionization, high saturation velocity)

13. Channel quantization
Channel quantization with decreasing channel thickness
Enhancement of the channel bandgap
Increment of threshold energy for i.i
=>reduces impact ionization effects in on-state breakdown

14. Application to InAs(1) Increment of Effective bandgap
Reduction of impact Ionization hole current
Reduction of saturation current level
Composite channel

15. Application to InAs(2) Structure A: L1=9nm, (single side doped)
Structure B:
L1=2nm, (single side doped)
Structure C:
L1=2nm, (double side doped)
Structure B
Structure C

16. Conclusion InAs Inserted HEMT Lowering Impact Ionization rate Merit:
Higher Gm
Higher Ft
Problem:
Low bias voltage limitation
(Low On-state breakdown voltage)
Lowering Impact Ionization rate
Composite channel
Channel quantization

17. Reference
Suppression of kink phenomenon in ultra-high-speed strained InAs- inserted E-mode HEMTs with a new 0.1 /spl mu/m Y-shaped Pt-buried gate and their impacts on device performance Dae-Hyun Kim; Tae-Woo Kim; Hun-Hee Noh; Jae-Hak Lee; Kwang-Seok Seo; Electron Devices Meeting, IEDM Technical Digest. IEEE International Dec Page(s):
First principles band structure calculation and electron transport for strained InAs Hori, Y.; Miyamoto, Y.; Ando, Y.; Sugino, O.; Indium Phosphide and Related Materials, 1998 International Conference on , 11-15 May Pages:
Improved InAlAs/InGaAs HEMT characteristics by inserting an InAs layer into the InGaAs channel Akazaki, T.; Arai, K.; Enoki, T.; Ishii, Y.; Electron Device Letters, IEEE , Volume: 13 , Issue: 6 , June Pages:
MBE growth of double-sided doped InAlAs/InGaAs HEMTs with an InAs layer inserted in the channel  • ARTICLE Journal of Crystal Growth, Volumes , Part 2, 1 May 1997, Pages M. Sexl, G. Böhm, D. Xu, H. Heiß, S. Kraus, G. Tränkle and G. Weimann
Impact of subchannel design on DC and RF performance of 0.1 μm MODFETs with InAs-inserted channel Xu, D.; Osaka, J.; Suemitsu, T.; Umeda, Y.; Yamane, Y.; Ishii, Y.; Electronics Letters , Volume: 34 , Issue: 20 , 1 Oct Pages:
High electron mobility 18,300 cm2/V·s InAlAs/InGaAs pseudomorphic structure by channel indium composition modulation Nakayama, T.; Miyamoto, H.; Oishi, E.; Samoto, N.; Indium Phosphide and Related Materials, Conference Proceedings., Seventh International Conference on , 9-13 May Pages: