Dale McMorrow Radiation Effects Section Naval Research Laboratory Washington, DC

1. Mechanisms of Ionization-Induced Carrier Transport and Collection in Next-Generation III-V Structures Dale McMorrow Radiation Effects Section Naval Research Laboratory Washington, DC

2. Outline • Objectives/Overview • Motivation • III-V Technology Overview • Radiation Effects in III-V Technologies • NextGen III-V Research Program • Technology Transfer

3. Description of the Effort • ABCS: Antimonide-Based Compound Semiconductors • To investigate, using both theory and experiment, the basic mechanisms of ionization-induced carrier deposition, transport, and collection in next-generation antimonide-based III-V compound semiconductor structures and materials • This is a collaborative effort between the Naval Research Laboratory and Vanderbilt University

4. Status of the Effort • Significant ongoing ABCS technology development • DARPA ABCS Program (2001-2006) • DARPA ISIS Program (2007-present) • Intel CRADA • Very little is understood about the performance of ABCS technologies in hostile environments • Experimental and theoretical databases are minimal • NRL has unique access to Sb-based technology, and has developed the experimental approaches necessary to address their response to ionizing radiation • Vanderbilt is ideally suited to take the lead on the theory/computational part of this effort

5. AlAs AlSb Wavelength, mm InP Energy Gap, eV GaAs GaSb InGaAs InAs Lattice Constant, mm III-V Semiconductor Material Systems

6. III-V Semiconductor Material Systems

7. Motivations: ABCS Electronics High-speed, low-power consumption electronics are needed for light-weightpower supplies, extension of battery lifetimes, and high data rate transmission • Low-noise receivers • space-based sensing and communications • portable communications • micro-air-vehicles (MAVs)

8. Motivations: ABCS Electronics • High-speed logic circuits • high-speed onboard processing • communications, data transmission • potential for lowest power-delay product • integration with RTDs for enhanced functionality and low-voltage operation • InP HEMTs presently hold the record current gain cutoff frequency for any three-terminal device

9. Motivations: ABCS Electronics • Sb-based electronics exhibit: • High electron mobility • High electron velocity • High sheet charge density • Large conduction band offset • <0.5 V operation / low power dissipation • Low noise • Digital circuits with speeds >100 GHz are anticipated

10. ABCS Technology Development • The NRL Microwave Technology Branch is a world leader in the growth, fabrication and characterization of Sb-based HEMTs, p-channel HFETs, and HBTs. • DARPA ABCS Program (2001-2006): • NRL teamed with Northrop-Grumman Space Technology (NGST, formerly TRW) to develop next-generation high-speed, low-power HEMT and HBT technology using antimonide heterostructures. • At the inception of the ABCS program, NRL had been in the forefront of the development of antimonide HEMT technology for more than seven years. • NRL’s superior material growth and device processing capabilities let to a record high cutoff frequency fT of 250 GHz, and a 90 GHz fT at a record low voltage of 0.1 volts • NRL growth and processing technology for antimonide HEMTs transferred to NGST via CRADA in FY03.

11. ABCS Technology Development • DARPA ABCS Program Major Milestones: • demonstration of an antimonide HEMT with a record maximum frequency of oscillation (fmax = 275 GHz) • Demonstration of an order of magnitude less power consumption than HEMTs based on competitive semiconductor material systems • The first antimonide-based X-band and W-band MMICs with state-of-the-art low-power performance Ref: J. Vac. Sci. Technol. B, 17 (3), May 1999

12. ABCS Technology Development • DARPA Integrated Structure is Sensor (ISIS) Program • NRL is again teamed with NGST • Continue to develop next-generation high-speed, low-power Sb-based HEMT technology. • Intel CRADA • NRL is also currently teamed with Intel, via a Cooperative Research and Development Agreement (CRADA), to develop advanced p-channel Sb HFETs for use in high-speed complementary logic applications

13. AlSb InAs 20 Å In0.4Al0.6As 40 Å AlSb 12 Å 1.0 InAs(Si) 12 Å AlSb 125 Å 0.5 InAs 100 Å AlSb 30 Å E0’ E1 InAs subchannel 42 Å Energy (eV) 0.0 E0 AlSb 500 Å Al 0.7Ga0.3Sb 0.3 mm -0.5 AlSb 1.7 mm InAs SI GaAs substrate -1.0 0 50 100 150 200 250 300 350 400 450 500 Distance (Å) In0.4Al0.6As InAs(Si) ABCS Technology: InAs HEMT 6.1 Å Lattice Spacing • 1.7 mm AlSb buffer layer on GaAs (SI) substrate: accommodates 8% lattice mismatch • InSb-like interfaces: high electron mobility • Modulation doping in thin InAs(Si) layer: sheet charge densities of 1-4 x 1012/cm2 • Large InAs/InAlAs valence band offset: lower leakage current from holes • InAs sub-channel reduces impact ionization: higher frequency operation

14. AlAs AlSb Wavelength, mm InP Energy Gap, eV GaAs GaSb InGaAs InAs Lattice Constant, mm III-V Semiconductor Material Systems

15. ABCS Technology: InAsSb HEMT InAsSb HEMT has attractive material properties and unique design flexibility enabling improved high-speed, low-power performance: • Higher electron mobility and velocity for higher speed. • Type I band alignment for lower leakage and lower noise figure. • Reach peak velocity at lower electric field for lower power consumption. • Complete structure is stable in air for increased stability. 6.2 Å Lattice Spacing

16. Radiation Effects in III-V FETs • III-V FETs typically are tolerant to high levels of ionizing radiation • Lack of native oxides • Dominated by displacement damage (DD) effects • III-V FET-based technologies typically are extremely susceptible to single-event effects • A primary goal of this program is to develop an understanding of the basic mechanisms of carrier transport and collection that lead to this SEE susceptibility

17. Rad Effects: TID/DD in III-V FETs • Recent work at NRL demonstrates that 6.1 Å ABCS technology is more tolerant than either GaAs or InP-based technologies • Due to strong carrier confinement in heterostructure wells • Weaver, et al., “High tolerance of InAs/AlSb high-electron-mobility transistors”, Appl. Phys. Lett, 87, 173501 (2005).

18. Rad Effects: SEE in III-V FETs • GaAs MESFETs and HFETs; Extensive work in 1990s: • Experiment and Simulation (NRL and others) • Charge collection and enhancement mechanisms fairly well understood • InP HEMTs: Limited experimental and simulation work • Experimental data similar to that of GaAs devices (NRL) • Simulation results inadequate but reveal significant differences • ABCS Devices: • HI and pulsed laser data on 6.1 Å technology (NRL) • No simulation results on 6.1 Å technology • No data/simulation on 6.2 Å or 6.3 Å technologies

19. Rad Effects: CC in GaAs HFETs Charge Enhancement 100 fC

20. Rad Effects: CC in GaAs HFETs

21. Rad Effects: CC in GaAs HFETs • 10X - 60X charge enhancement observed • HI and laser excitation • Associated with S-D current (from power supply) • Barrier lowering at source-substrate barrier • device turned “on” • Associated with charge deposited below active region • 1 mm to 2 mm most effective • Current pathway from source, deep through substrate, to drain

22. Hole Density Electron Density Rad Effects: CC in InP HEMTs G G • Experiment • Device simulation • Mechanisms are significantly different from GaAs t<0 ps 50 ps 400 ps cutline cutline

23. Rad Effects: CC in InP HEMTs 1e18 (600 ps) Carrier Injection and S-D Current Confined to InGaAs Channel

24. Excess Hole Density in InAlAs buffer: appx.1015 cm-3 Rad Effects: CC in InP HEMTs

25. Rad Effects: Bulk vs. HEMTs Bulk (GaAs MESFET) InP HEMT

26. Rad Effects: AlSb/InAs HEMTs

27. Technical Approach • OBJECTIVE: To investigate, using both theory and experiment, the basic mechanisms of ionization-induced carrier deposition, transport, and collection in next-generation antimonide-based III-V compound semiconductor structures and materials. • APPROACH: • Experiment: measurement of charge collection transients in 6.1 Å and 6.2 Å ABCS test structures • Theory: develop a theoretical description to describe the highly non-equilibrium state induced in heterosructure devices by ionizing radiation; use the experimental data to validate and calibrate the theory

28. Technical Approach • Experimental Approach (NRL): • Test structure selection • Packaging in high-bandwidth packages • High-bandwidth transient measurement • Statistical analysis of ion-induced transients • Theoretical Approach (VU): • Develop a theoretical description • Evaluate capabilities of various commercial codes and determine suitability • Use the experimental data to validate and calibrate the theory • Identify the basic mechanisms of carrier transport and collection that are responsible for shaping the data

29. Technical Approach • High-bandwidth (12-20 GHz), single-shot transient measurement • Permits direct measurement of ion-induced transients for single ion strikes for the first time

30. Technical Approach • Theoretical Approach (VU): • One graduate student assigned to this project (Sandeepan DasGupta) • Vanderbilt will provide access to its Advanced Computing center for Research and Education (ACCRE), which houses their Beowulf cluster supercomputer

31. Progress • Initial test structures selected • Mounted in high-bandwidth packages • Tested for dc operational characteristics • Heavy-Ion test scheduled for June • Vanderbilt student (Sandeepan DasGupta) is getting started • Reading literature • Evaluating available commercial codes • Asking questions

32. Key Personnel • NRL Solid State Electronics Branch • Radiation Effects Branch (McMorrow, Warner) • NRL Microwave Technology Branch • Brad Boos • Vanderbilt/ISDE • Robert Reed • Ron Schrimpf • Grad student

33. Technology Transfer • NRL ABCS technology development program • ISDE Engineering • Collaborative R&D, e.g. NRL/Vanderbilt • DoD vendor relationships • NASA Goddard • Through students