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

3. UNCLASSIFIED 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. UNCLASSIFIED 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. UNCLASSIFIED III-V Semiconductor Material Systems Lattice Constant,  m Energy Gap, eV Wavelength,  m GaAs AlSb InAs GaSb InGaAs AlAs InP

6. UNCLASSIFIED III-V Semiconductor Material Systems

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

8. UNCLASSIFIED 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 Motivations: ABCS Electronics

9. UNCLASSIFIED 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 Motivations: ABCS Electronics

10. UNCLASSIFIED 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 f T of 250 GHz, and a 90 GHz f T 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. UNCLASSIFIED ABCS Technology Development DARPA ABCS Program Major Milestones: demonstration of an antimonide HEMT with a record maximum frequency of oscillation (f max = 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. UNCLASSIFIED 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. UNCLASSIFIED 1.7  m 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 10 12 /cm 2 Large InAs/InAlAs valence band offset: lower leakage current from holes InAs sub-channel reduces impact ionization: higher frequency operation 050100150200250300350400450500 -0.5 0.0 0.5 1.0 AlSb In 0.4 Al 0.6 As InAs InAs(Si) E1E1 E0E0 E0’E0’ Distance (Å) Energy (eV) ABCS Technology: InAs HEMT AlSb 125 Å InAs(Si) 12 Å AlSb 12 Å InAs 20 Å In 0.4 Al 0.6 As 40 Å SI GaAs substrate AlSb 1.7  m InAs 100 Å AlSb 30 Å InAs subchannel 42 Å AlSb 500 Å Al 0.7 Ga 0.3 Sb 0.3  m 6.1 Å Lattice Spacing

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

15. UNCLASSIFIED ABCS Technology: InAsSb HEMT 6.2 Å Lattice Spacing 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. InAsSb HEMT has attractive material properties and unique design flexibility enabling improved high-speed, low-power performance:

16. UNCLASSIFIED 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 Radiation Effects in III-V FETs

17. UNCLASSIFIED 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). Rad Effects: TID/DD in III-V FETs

18. UNCLASSIFIED 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 Rad Effects: SEE in III-V FETs

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

20. UNCLASSIFIED Rad Effects: CC in GaAs HFETs

21. UNCLASSIFIED 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  m to 2  m most effective Current pathway from source, deep through substrate, to drain Rad Effects: CC in GaAs HFETs

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

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

24. UNCLASSIFIED Excess Hole Density in InAlAs buffer: appx. 10 15 cm -3 Rad Effects: CC in InP HEMTs

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

26. UNCLASSIFIED Rad Effects: AlSb/InAs HEMTs

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