Microwave Microelectronics Laboratory

Department of Electrical Engineering, USCResearch Focus:

- Wide Bandgap Microwave Power Devices and Integrated Circuits

- Physics, Simulation, Design and Characterization

The research in the Microwave Microelectronic Lab is focused on high power high frequency devices and ICs made of GaN and

related wide bandgap semiconductors. These devices are capable of delivering record high power density, operating in a broad temperature range from cryogenic up to at least 300 C; they are robust and chemically stable. These features make GaM microwave

devices best candidates to replacing many of existing components, from Si devices in power conversion systems to MEMS in microwave switches.

The group has demonstrated low loss high power microwave switches, power limiters and other devices and ICs which outperform

most of existing traditional devices. The group also works on GaN based components for power electronic applications.

1

III-Nitride microwave switches

Grigory Simin

Department of Electrical Engineering, University of South Carolina, Columbia, SC

simin@cec.sc.edu

2

Microwave switch applications

Microwave switches are

essential components in

nearly any modern RF

and microwave systems

Reconfigurable

phase-shifters in

phased-array

antennasMicrowave switches in

iPad

Microwave switches in 3G

cell communications

Satellite communications

with on-board switching

systems

Receiver

Transmitter Switch

Transmitter-receiver

switches in radars

3

III-N HFET is a new paradigm in RF

switching

M. S. Shur, A. D. Bykhovski, R. Gaska, Sol.St. Elec., Vol. 44, pp. 205-210 (2000)

AlGaN/GaN

heterostructure induces

2DEG with sheet

densities up to 5×1013 cm-

2

forming metal-like

conducting plane

SiC

GaN

AlGaN

0

1

2

3

4

5

6

7

0 0.2 0.4 0.6 0.8 1

Al Molar Fraction

1

2

34

30 nm

10 nm

5 nm

Ignoring the dislocation array development

Critical barrier thickness

4

MOSHFET RF switch concept

ON state VG=0

Ron

Vg

OFF state

VG < VT

Coff

Vg

S G D

F E T

In p u t O u tp u t

V G

S G D

F E T

In p u t O u tp u t

V G

SiC

GaN

AlGaN

SiO2

S DG

5

State-of-the-art III-N MOSHFET

AlGaN/GaN 2DEG:

µµµµ ≅≅≅≅ 1800 cm2/V-snS ≅≅≅≅ 1.5 ×1013 cm-2

RSH ≤ 230 Ω/Ω/Ω/Ω/Sq.

~ 0.065 dB3-mm gate periphery MOSHFET

~ 0.2 dB-mmTotal RON ~ 1.65 Ω-mm

~ 0.09 dB-mmContact RC ~ 0.5 Ω-mm

~ 0.1 dB-mm5 µm S-D spacing, RSD ~ 1.15 Ω-mm

Insertion lossDevice component

SiC

GaN

AlGaN

S DGSiO2

6

MOSHFET vs. other RF switching devices

ExcellentGoodMediocre GoodReliability

ExcellentMediocrePoorPoorTemperature, chemical, radiation stability

LowSimpleSimpleRequires LC filters

Biasing network

LowLowLowHighDC power consumption

Up to 100 W< 1 W< 1 W< 10 WHandling powers

> 30 dB> 25 dB> 40 dB> 30 dBIsolation

0.05…1.5 dB0.2…2.5 dB0.1…5 dB0.3…1.5 dBInsertion loss

Planar – IC Planar - ICPlanar – ICdiscrete devices

Technology

III-N MOSHFETs

GaAs HEMTsRF MEMSPin-diodesCharacteristic

7

Typical circuit for low-loss high isolation

RF switch

Effect of RON and COFF on series/shunt RF switch

IC performance

RF input

Z0=50Ω

RF output

Z0=50Ω

D1

D2

V1

V2RG1

RG2

Higher RON: • increases the insertion loss provided by the series device D1

• decreases the isolation provided by the shunt device D2

Higher COFF: • increases the insertion loss provided by the shunt device D2

• decreases the isolation provided by the series device D1

8

0.5 1.0 1.5 2.0-1.0

-0.8

-0.6

-0.4

-0.2

0.0

-40

-30

-20

-10

Isola

tio

n (

dB

)

Inse

rtio

n L

oss (

dB

)

Frequency (GHz)

Insertion loss (no metal loss)

Isolation

Insertion loss (thin metal)

III-N Single-pole, single-throw (SPST)

switch MMIC

9

Insertion loss and isolation of III-Nitride Single-pole double-throw integrated MOSHFET RF switch

0.5 1.0 1.5 2.0 2.5-60

-50-40-30

-20

-3.0-2.5-2.0-1.5-1.0-0.50.0

OFF

ONR

F T

ransm

issio

n, dB

Frequency, GHz

0.5 1.0 1.5 2.0 2.5-60

-50-40-30

-20

-3.0-2.5-2.0-1.5-1.0-0.50.0

OFF

ONR

F T

ransm

issio

n, dB

Frequency, GHz

III-N Single-pole, double-throw (SPDT)

switch MMIC

10

20 25 30 35 40 45 500

25

50

75 HP ADS simulations

Measured at 10 GHz

VT -

VG,

V OFF

Peak switching Power, dBm

0.5

1.0

1.5

2.0 HP ADS simulations

Measured at 10 GHz

ID

S,

AON

PON ~ IDS2×RL

2

OFFP ~ ( ) /G T L

V V R−

III-N MOSHFET RF Switch maximum RF powers

11

Maximum switching power measured

RF power is limited by the available power source

MOSHFET

12

2 4 6 8 10

-4

-2

0

Inse

rtio

n L

oss, d

B

Frequency, GHz

RT 50oC

100oC 150oC

200oC 250oC

2 4 6 8 10

-40

-35

-30

-25

-20

-15

-10

-5

0 RT 50oC

100oC 150oC

200oC 250oC

Isola

tion, dB

Frequency, GHz

III-N MOSHFET RF Switch temperature stability

Tested temperature range limited by the probe station specs

13

Cryogenic performance

TLM data for MOSHFET RF switch at

77K and room temperature.

300K: Rsh=268 W/sq; Rc= 0.45 W×mm;

77K: Rsh=92 W/sq Rc= 0.36 W×mm;

Single shunt MOSHFET in a 50-W CPW.RF transmission at room temperature and at 77K

0 2 4 6 8 1012141618202224

5

10

15

20

25

30

35

Liquid N

Room temp.

Electrode spacing

Re

sis

tan

ce

, Ω

0 2 4 6 8 1012141618202224

5

10

15

20

25

30

35

Liquid N

Room temp.

Electrode spacing

Re

sis

tan

ce

, Ω

1.0 1.1 1.2 1.3-16

-14

-12

-10

-8

-6

-4

-2

0

OFF (VG = 0)

ON (VG <V

T)

RT

77K

Tra

nsm

issio

n, d

BFrequency, GHz

14

0 100 200 300 400 500

0.0

0.1

0.2

0.3

0.4

0.5

0.6 Pulsed

DC (OFF)

DC (ON)

RF

dete

cto

r sig

nal, a

.u.

Time, nS

0 40 80 120 160 2000.0

0.1

0.2

0.3

0.4

0.5

0.6 Pulsed

DC (OFF)

DC (ON)

RF

dete

cto

r sig

nal, a

.u.

Time, µS

100 ns pulses

50 µµµµs pulses

No large-signal RF dispersion (no current collapse)

Switching time is driver-circuit limited (ns range expected)

III-N MOSHFET RF Switch switching speed

15

Millimeter-wave III-N C3-MOSHFET RF Switch

SiC

GaN

AlGaN

SiO2

S DGOUT

SiC/sapphire

GaN

AlGaN

SiO2

SiC

GaN

AlGaN

SiO

2

S DG

Ohmic contacts

• High-T annealing

• Tight Gate alignment

C3 MOSHFET

• No annealed contacts

• Alignment-free technology

16

C3 HFET vs. regular HFET RF-switch

RF InputRF Output

5 10 15 20-6

-5

-4

-3

-2

-1

0

C3MOSHFET

MOSHFET

VG = 0 (ON )

Frequency GHz

Tra

nsm

issi

on, dB

RF In RF Out

VG

HFET

HFET

5 10 15 20-6

-5

-4

-3

-2

-1

0

C3MOSHFET

MOSHFET

VG = 0 (ON )

Frequency GHz

Tra

nsm

issi

on, dB

RF In RF Out

VG

HFET

HFET

5 10 15 20

-40

-35

-30

-25

-20

-15

-10

C3MOSHFET

MOSHFET

VG

= -10 V

(OFF)

Frequency GHz

Tra

nsm

issio

n, dB

RF In RF Out

VG

HFET

HFET

5 10 15 20

-40

-35

-30

-25

-20

-15

-10

C3MOSHFET

MOSHFET

VG

= -10 V

(OFF)

Frequency GHz

Tra

nsm

issio

n, dB

RF In RF Out

VG

HFET

HFET

OUT

SiC/sapphire

GaN

AlGaN

SiO2

SiC

GaN

AlGaN

SiO2

S DG

OUT

SiC/sapphire

GaN

AlGaN

SiO2

SiC

GaN

AlGaN

SiO2

S DG

17

20 22 24 26 28 30 32 34 36 38 40

-35

-30

-25

-20

-15

-10

-5

0ON

VG1

=0

VG2

=

-12V

-16V

Tra

nsm

issio

n (

dB

)

Pin (dBm)

OFF

VG2

=0

VG1

=

-12V

-16V

-20V

1 2 3 4 5 6 7 8 9 10 11 12-35

-30

-25

-20

-15

-10

-5

0

Insertion Loss

Frequency (GHz)1 2 3 4 5 6 7 8 9 10 11 12

-35

-30

-25

-20

-15

-10

-5

0

Isolation

Insert

ion L

oss &

Isola

tion (

dB

)C3 MOSHFET RF Switch MMIC

10 GHz CWSmall-signal

DS

VG1

VG2DP1

DP2

L

18

C3 – HfO2 RF Switch

GaN

AlGaN

2D gas

HfO2

So

urc

e(R

F i

n)

Gate Dra

in(R

F o

ut)

GaN

AlGaN

2D gas

HfO2

So

urc

e(R

F i

n)

Gate Dra

in(R

F o

ut)

GaN

AlGaN

2D gas

HfO2

So

urc

e(R

F i

n)

Gate Dra

in(R

F o

ut)

0 2 4 6 8 10-5

-4

-3

-2

Insert

ion L

oss, dB

Frequency, GHz

2 4 6 8 10-30

-25

-20

-15

-10

-5

0

5

Isola

tion, dB

Frequency, GHz

HFET

MOSHFET

A. Koudymov, N. Pala, V. Tokranov, S. Oktyabrsky, M. Gaevski, R. Jain, J. Yang, X. Hu, M. Shur, R. Gaska, G. Simin, HfO2 - III-Nitride RF Switch with Capacitively-Coupled Contacts, IEEE EDL, V. 30, Issue 5, pp:478 - 480 (2009)

19

Multigate C3- RF switches

Experimental multigate RF switch (W = 200 µm, LG = 0.25 µm)Capacitively-coupled contacts (C3) – no annealed ohmic contacts

20

1 2 3 4

-18

-17

-16

-15

-14

-13

Isola

tio

n (

dB

)

Number of Gates1 2 3 4 5 6 7 8 9 10

-45

-40

-35

-30

-25

-20

-15

-4-3-2-10

Insertion Loss (1...4 gates)

Single Gate

2 Gates

4 Gates

Inse

rtio

n L

oss

/ I

sola

tion

(d

B)

Frequency (GHz)

Dots - 2D simulations

C3 multigate RF switch (W = 200 mm, LG = 0.25 mm)

10 GHz isolation

Multigate C3- RF switches

G. Simin, B. Khan, A. Koudymov, M. Gaevski, R. Jain, J. Yang, X. Hu, R. Gaska, and M. Shur, GaN Multigate RF Switches with Capacitively-Coupled Contacts. IEEE El. Dev. Lett, V. 30, N9 pp. 895-897 (2009)

21

Side-Gated C3 RF Switch

Substrate

RF Input

Channel RF Output

ControlControl

C3 electrodes

C3 or O

hmic

electro

des

C3 or O

hmic

electro

des

Substrate

RF Input

Channel RF Output

ControlControl

C3 electrodes

C3 or O

hmic

electro

des

C3 or O

hmic

electro

des

No gate electrode in the RF Input-output regionSide-gate electrode controls the impedance of C3 contactsthus turning switch ON and OFF

Control

C3

RF OutputRF Input

ControlC3

Control

C3

RF OutputRF Input

Control

C3

Control

C3

RF OutputRF Input

ControlC3

Control

C3

RF OutputRF Input

Control

C3

22

Side-gated C3- series test element

Control electrode

Experimental data and comparison with C3 - models

W=50 µµµµm

0 5 10-8

-7

-6

-5

-4

-3

-2

-1

0

C3 2um gap

W=50 um Series

ON

C3

HFET

Insert

ion L

oss, dB

Frequency, GHz

23

Side-gated C3- SPST

RF input – output interdigitated fingers

Control electrode

Single control electrode controls the ON/OFF state of the multi-finger C3-device

24

Side-gated C3- SPST performance

0 2 4 6 8 10 12-10

-8

-6

-4

-2

0

MOS C3 SPST

0.3 dB @ 6 GHz

Inse

rtio

n L

oss,

dB

Frequency, GHz

0 2 4 6 8 10 12

-45

-40

-35

-30

-25

-20

-15

-10

27.5dB @ 6 GHz

MOS C3 SPST

Isola

tion,d

BFrequency, GHZ

Small-signal insertion loss and isolation

Control electrodes bias

ON-state: VSER = 0; VSHT=10V;

OFF-state: VSER = 10V; VSHT=0;