Single Event Transient Response of InGaAs MOSFET Kai Ni 1 , En Xia - PowerPoint PPT Presentation

Single Event Transient Response of InGaAs MOSFET Kai Ni 1 , En Xia Zhang 1 , Nicholas C. Hooten 1 , William G. Bennett 1 , Michael W. McCurdy 1 , Ronald D. Schrimpf 1 , Robert A. Reed 1 , Daniel M. Fleetwood 1 , Michael L. Alles 1 , Tae-Woo Kim 2 , Jianqiang Lin 3 , Jesús A. del Alamo 3 1 Vanderbilt University, Nashville, TN 37235, USA 2 SEMATECH 3 Massachusetts Institute of Technology, Cambridge, MA 02139 USA 6/23/14 RER group meeting 1

Motivation • III-V materials are promising channel candidates at beyond 14nm technology node • Previous transient studies focus on III-V MESFET/HEMT • Gate transients • Charge enhancement due to source drain pathway • Gate bias dependence shows a peak at threshold voltage • It’s important to study the transient response of III-V MOSFET 6/23/14 RER group meeting 2

Device II • Cross section and vertical band diagram Conduction Band 2 Fermi Level Valance Band 1 0 energy (eV) -1 -2 -3 -4 0.00 0.02 0.04 0.06 0.08 position ( µ m) 6/23/14 RER group meeting 3

Heavy Ion Results • No gate transient due to large barrier • Source and drain transient have the same magnitude • Two processes with different time constant • Fast collection: τ≈ 100 ps, direct 0.3 collection drain source • Slow collection: τ≈ 3 ns, source-to- 0.2 gate drain pathway 0.1 current (mA) 0.0 -0.1 -0.2 -0.3 0 10 20 30 40 50 time (ns) 6/23/14 RER group meeting 4

Gate Bias Dependence • Peak drain current reaches a maximum around threshold voltage 0.36 0.34 peak drain current (mA) 0.32 0.30 0.28 0.26 0.24 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 V GS -V TH (V) • Peak drain current decreases considerably in inversion and slightly in depletion and accumulation 6/23/14 RER group meeting 5

Laser Irradiation • Laser wavelength 1.26 μm • Photon energy 0.98 eV, larger than the channel material bandgap, smaller than the other matherials 10 µ m XX’ 4 µ m 40 µ m 6/23/14 RER group meeting 6

Laser Results • Line scan • The drain side strike has a larger peak drain current than the source side strike • The drain side has a higher electric field than the source side ( V DS =0.5 V), so the electron velocity is higher in drain side, the peak drain current is larger 2.5 peak drain current (mA) 2.4 2.3 2.2 Source Drain 2.1 2.0 -2 -1 0 1 2 x position ( µ m) 6/23/14 RER group meeting 7

Gate Bias Dependence • The laser data is consistent with heavy ion data 2.5 2.4 peak drain current (mA) 2.3 2.2 2.1 2.0 1.9 1.8 1.7 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 V GS -V TH (V) • The peak drain current is maximum around threshold and decreases considerably in inversion while slightly in depletion and accumulation 6/23/14 RER group meeting 8

2D TCAD Simulation • Model HfO2 gate InGaAs InGaAs InGaAs InAlAs X Y source drain Y’ 0 Y (µm) 0.2 -0.4 -0.2 0 0.2 0.4 X’ X (µm) The LET is 0.1 pC/ μm • • The ion strike is gaussian both in space and time The strike center is at 0.2 μm and 1.0 ns • 6/23/14 RER group meeting 9

2D TCAD Simulation • Hole density (colored map) and electrical potential (contour) Hole Density -0.2 -0.2 1.0 ns Pre Strike -0.1 -0.1 0 0 0.1 0.1 0.2 0.2 0.3 0.3 0.1 0.2 0.3 -0.2 -0.1 0 0.1 0.2 0.3 -0.2 -0.1 0 • At the center of the strike, the electric potential is strongly distorted due to a large number of electrons and holes are generated around the strike location 6/23/14 RER group meeting 10

2D TCAD Simulation • Hole density (colored map) and electrical potential (contour) -0.2 -0.2 1.2 ns 1.0 ns -0.1 -0.1 Y (µm) 0 0 0.1 0.1 0.2 0.2 0.3 0.3 -0.2 -0.1 0 0.1 0.2 0.3 X (µm) -0.2 -0.1 0 0.1 0.2 0.3 • At 1.2 ns, the electric potential in the buffer recovers. Electrons and holes move to the channel layer. Only the channel layer is strongly perturbed 6/23/14 RER group meeting 11

2D TCAD Simulation • Conduction band along the horizontal cut and vertical cut 1.0 ps 0.4 3.0 1.0 ns 1.0 ps 1.2 ns 0.2 2.5 1.0 ns 1.6 ns conduction band (eV) 1.2 ns 2.1 ns 0.0 2.0 1.6 ns conduction band (eV) 6.0 ns 2.1 ns 10.0 ns -0.2 1.5 6.0 ns 10.0 ns -0.4 1.0 -0.6 0.5 -0.8 0.0 -1.0 -0.5 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 -0.01 0.00 0.01 0.02 0.03 0.04 x position ( µ m) y position ( µ m) • Electric field exists before strike to stop holes entering channel, but it is almost zero after strike. Electrons and holes flood into the channel • Electric potential is distorted around the strike location at the center of strike (1.0 ns) but recovers quickly • At pre-strike, the source-channel barrier is 0.52 eV, but reduces to 0.03 eV at 1.2 ns. The device is ON • The source-channel barrier is slowly recovered, which lasts for a few nanoseconds 6/23/14 RER group meeting 12

2D TCAD Simulation • Conduction band and excess electron density at different gate biases 18 -0.40 9x10 V GS =-0.4 V 18 8x10 -0.45 V GS =-0.2 V -3 ) conduction band energy (eV) 18 V GS = 0.2 V excess electron density (cm 7x10 -0.50 V GS = 0.4 V 18 6x10 -0.55 18 5x10 -0.60 18 4x10 V GS =-0.4 V -0.65 V GS =-0.2 V 18 3x10 -0.70 V GS = 0.2 V 18 2x10 V GS = 0.4 V -0.75 18 1x10 -0.80 0 0.000 0.002 0.004 0.006 0.008 -0.4 -0.2 0.0 0.2 0.4 y position ( µ m) x position ( µ m) • The voltage drop along the channel region decreases with gate bias, leading to smaller horizontal electric field, hence smaller velocity • The absolute excess electron density, the difference between post-strike and pre- strike electron density, reaches a maximum around threshold, decreases considerably in inversion and slightly in depletion and accumulation 6/23/14 RER group meeting 13

Comparison • Comparison of the gate bias dependence between heavy ion, laser and 2D TCAD simulation 1.05 1.00 normalized peak current 0.95 0.90 0.85 Laser Results 0.80 Heavy Ion Results 0.75 2D TCAD Simulation 0.70 0.65 0.60 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 V GS -V TH (V) • The heavy ion data, the laser data and 2D TCAD simulation data agree very well 6/23/14 RER group meeting 14

Conclusion  No gate transients due to large barrier for both electron and hole between gate dielectric and semiconductor  The slow holes piling up under the gate and the source access region modulates the source channel barrier, turning ON the device and enhancing the collected charge  The peak drain current is maximum for gate biases around threshold and decreases considerably in inversion and slightly in depletion and accumulation  Depending on the application and the opportunities for remediation, these transient responses may impose limitations on the use of some types of alternative-channel materials in space applicaiton 6/23/14 RER group meeting 15