Microwave Microelectronics Laboratory Department of Electrical Engineering, USC Research 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
Microwave switch applications Microwave switches are essential components in nearly any modern RF and microwave systems Receiver Transmitter Switch Microwave switches in 3G cell communications Transmitter-receiver switches in radars Microwave switches in ipad Satellite communications with on-board switching systems Reconfigurable phase-shifters in phased-array antennas 2
3 7 6 5 4 3 2 1 0 III-N HFET is a new paradigm in RF switching Ignoring the dislocation array development Critical barrier thickness 30 3 nm 4 10 nm 2 nm1 0 0.2 0.4 0.6 0.8 1 5 Al Molar Fraction AlGaN GaN AlGaN/GaN heterostructure induces 2DEG with sheet densities up to 5 10 13 cm - M. S. Shur, A. D. Bykhovski, R. Gaska, Sol.St. Elec., Vol. 44, pp. 205-210 (2000) SiC 2 forming metal-like conducting plane
4 MOSHFET RF switch concept S G D V G SiO 2 S G D AlGaN F E T GaN In p u t O u tp u t SiC Vg Vg ON state V G =0 Ron Coff OFF state V G < V T
5 State-of-the-art III-N MOSHFET S SiO 2 G D AlGaN/GaN 2DEG: AlGaN GaN SiC µ 1800 cm 2/ V-s n S 1.5 10 13 cm -2 R SH 230 Ω/Sq. Device component 5 µm S-D spacing, R SD ~ 1.15 Ω-mm Contact R C ~ 0.5 Ω-mm Total R ON ~ 1.65 Ω-mm Insertion loss ~ 0.1 db-mm ~ 0.09 db-mm ~ 0.2 db-mm 3-mm gate periphery MOSHFET ~ 0.065 db
6 MOSHFET vs. other RF switching devices Characteristic Pin-diodes RF MEMS GaAs HEMTs III-N MOSHFETs Technology discrete devices Planar IC Planar - IC Planar IC Insertion loss 0.3 1.5 db 0.1 5 db 0.2 2.5 db 0.05 1.5 db Isolation > 30 db > 40 db > 25 db > 30 db Handling powers < 10 W < 1 W < 1 W Up to 100 W DC power consumption High Low Low Low Biasing network Requires LC filters Simple Simple Low Temperature, chemical, radiation stability Poor Poor Mediocre Excellent Reliability Good Mediocre Good Excellent
Typical circuit for low-loss high isolation RF switch Effect of R ON and C OFF on series/shunt RF switch IC performance RF input Z 0 =50Ω D 1 RF output Z 0 =50Ω R G1 D 2 R G2 V 2 V 1 Higher R ON : increases the insertion loss provided by the series device D 1 decreases the isolation provided by the shunt device D 2 Higher C OFF : increases the insertion loss provided by the shunt device D 2 decreases the isolation provided by the series device D 1 7
8 III-N Single-pole, single-throw (SPST) switch MMIC 0.0 Insertion loss (no metal loss) -10 Insertion Loss (db) -0.2-0.4-0.6-0.8-1.0 Insertion loss (thin metal) Isolation 0.5 1.0 1.5 2.0 Frequency (GHz) -20-30 -40 Isolation (db)
9 III-N Single-pole, double-throw (SPDT) switch MMIC RF Transmission, db 0.0-0.5-1.0-1.5-2.0-2.5-3.0-20 -30-40 -50-60 ON OFF 0.5 1.0 1.5 2.0 2.5 Frequency, GHz Insertion loss and isolation of III-Nitride Single-pole double-throw integrated MOSHFET RF switch
10 III-N MOSHFET RF Switch maximum RF powers I DS, A V T - V G, V 2.0 1.5 1.0 0.5 75 50 25 ON P ON ~ I DS2 R L OFF HP ADS simulations Measured at 10 GHz HP ADS simulations Measured at 10 GHz 2 P OFF ~ ( VG VT ) / RL 0 20 25 30 35 40 45 50 Peak switching Power, dbm
11 Maximum switching power measured MOSHFET RF power is limited by the available power source
12 III-N MOSHFET RF Switch temperature stability Insertion Loss, db 0-2 -4 RT 50 o C 100 o C 150 o C 200 o C 250 o C Isolation, db 0-5 -10-15 -20-25 -30-35 -40 RT 50 o C 100 o C 150 o C 200 o C 250 o C 2 4 6 8 10 Frequency, GHz 2 4 6 8 10 Frequency, GHz Tested temperature range limited by the probe station specs
13 Cryogenic performance Resistance, Ω 35 30 25 20 15 10 5 Room temp. 0 2 4 6 8 1012141618202224 Electrode spacing TLM data for MOSHFET RF switch at 77K and room temperature. Liquid N 300K: R sh =268 W/sq; R c = 0.45 W mm; 77K: R sh =92 W/sq R c = 0.36 W mm; Transmission, db 0-2 -4-6 -8-10 -12-14 RT 77K ON (V G <V T ) OFF (V G = 0) -16 1.0 1.1 1.2 1.3 Frequency, GHz Single shunt MOSHFET in a 50-W CPW. RF transmission at room temperature and at 77K
14 III-N MOSHFET RF Switch switching speed RF detector signal, a.u. 0.6 DC (ON) Pulsed 0.5 0.4 0.3 0.2 0.1 0.0 DC (OFF) 0 100 200 300 400 500 Time, ns RF detector signal, a.u. 0.6 DC (ON) Pulsed 0.5 0.4 0.3 0.2 0.1 DC (OFF) 0.0 0 40 80 120 160 200 Time, µs 100 ns pulses 50 µs pulses No large-signal RF dispersion (no current collapse) Switching time is driver-circuit limited (ns range expected)
15 Millimeter-wave III-N C 3 -MOSHFET RF Switch S G SiO 2 D S G SiO 2 D OUT AlGaN 2 AlGaN GaN GaN SiC SiC/sapphire Ohmic contacts High-T annealing Tight Gate alignment C 3 MOSHFET No annealed contacts Alignment-free technology
16 C 3 HFET vs. regular HFET RF-switch RF Input S G SiO 2 AlGaN D OUT RF Output GaN SiC/sapphire Transmission, db 0-1 -2-3 -4-5 -6 V G = 0 (ON ) RF In RF Out V G C 3 MOSHFET MOSHFET 5 10 15 20 Frequency GHz Transmission, db -10-15 -20-25 -30-35 -40 V G = -10 V (OFF) RF In RF Out V G C 3 MOSHFET MOSHFET 5 10 15 20 Frequency GHz
17 C 3 MOSHFET RF Switch MMIC V G1 L D S D P1 V G2 D P2 Insertion Loss & Isolation (db) 0-5 Insertion Loss -10-15 -20-25 Small-signal -30 Isolation -35 1 2 3 4 5 6 7 8 9 10 11 12 Frequency (GHz) Transmission (db) 0-5 -10-15 -20-25 -30-35 OFF V G2 =0 V G1 = -12V -16V -20V ON V G1 =0 V G2 = -12V -16V 10 GHz CW 20 22 24 26 28 30 32 34 36 38 40 Pin (dbm)
C 3 HfO 2 RF Switch -2 Source (RF in) AlGaN Gate GaN HfO 2 2D gas Drain (RF out) Insertion Loss, db -3-4 Isolation, db -5 0 2 4 6 8 10 Frequency, GHz 5 0-5 -10-15 -20-25 -30 HFET MOSHFET 2 4 6 8 10 Frequency, GHz 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) 18
19 Multigate C 3 - RF switches Experimental multigate RF switch (W = 200 µm, L G = 0.25 µm) Capacitively-coupled contacts (C 3 ) no annealed ohmic contacts
Multigate C 3 - RF switches Insertion Loss / Isolation (db) 0-1 -2-3 -4-15 -20-25 -30-35 -40 Insertion Loss (1...4 gates) Single Gate 2 Gates 4 Gates Dots - 2D simulations -45 1 2 3 4 5 6 7 8 9 10 Frequency (GHz) Isolation (db) -13-14 -15-16 -17-18 10 GHz isolation 1 2 3 4 Number of Gates C 3 multigate RF switch (W = 200 mm, LG = 0.25 mm) 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) 20
21 Side-Gated C 3 RF Switch Substrate C 3 or Ohmic electrodes RF Input Control Control C 3 electrodes Channel RF Output C 3 or Ohmic electrodes RF Input Control C 3 RF Input Control C 3 RF Output Control C 3 RF Output Control C 3 No gate electrode in the RF Input-output region Side-gate electrode controls the impedance of C 3 contacts thus turning switch ON and OFF
22 Side-gated C 3 - series test element Control electrode W=50 µm Insertion Loss, db 0-1 -2-3 -4-5 HFET C3 C3 2um gap -6 W=50 um Series -7 ON -8 0 5 10 Frequency, GHz Experimental data and comparison with C 3 - models
23 Side-gated C 3 - SPST Control electrode RF input output interdigitated fingers Single control electrode controls the ON/OFF state of the multi-finger C3-device
Side-gated C 3 - SPST performance Insertion Loss, db 0-2 -4-6 -8 MOS C3 SPST 0.3 db @ 6 GHz -10 0 2 4 6 8 10 12 Frequency, GHz Isolation,dB -10-15 -20-25 -30-35 -40-45 27.5dB @ 6 GHz MOS C3 SPST 0 2 4 6 8 10 12 Frequency, GHZ Small-signal insertion loss and isolation Control electrodes bias ON-state: V SER = 0; V SHT =10V; OFF-state: V SER = 10V; V SHT =0; 24