1. Professor Ronald L. Carter ronc@uta.edu http://www.uta.edu/ronc/
EE5342 – Semiconductor Device Modeling and Characterization Lecture 11 - Spring 2005
Professor Ronald L. Carter
L11 February 22

2. Project 1
Some initial data and assignments for Project 1 are posted at
and
L11 February 22

3. Additional Project 1 Actions
Develop the best least squares* static model (IS, N, ISR, NR, RS) for operating the diode in the range 700mV < vext < 1000mV *i.e. minimize
Repeat for the range 300mV to 1V
L11 February 22

4. SPICE Diode A.C. Parameters
L11 February 22

5. SPICE Diode Static I-V
Id,ext (A)
Vd,ext (V)
L11 February 22

6. Small signal diode Z-parameter**
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7. SPICE Diode Re{Z} Re{Z} (Ohms) Frequency (Hz) (2pTT)-1 1 mA 10 mA
CJ0 = 1E-12
VJ = 0.75
M = 0.5
TT = 1E-9
(2pTT)-1
1 mA
100 pA
1 nA
10 nA
100 nA
10 mA
100 mA
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8. Small signal low and high freq. limits for Z-par.**
L11 February 22

9. SPICE Diode Temp. Eqs.1
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10. Corrections in some versions of SPICE
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11. SPICE Diode Temp. Pars.1 PARAMETER definition and units default value
XTI IS temperature exponent 3.0
TIKF ikf temperature coefficient (linear) °C
TRS1 rs temperature coefficient (linear) °C
TRS2 rs temperature coefficient (quadratic) °C
TBV1 bv temperature coefficient (linear) °C
TBV2 bv temperature coefficient (quadratic) °C
T_ABS absolute temperature °C
T_MEASURED measured temperature °C
T_REL_GLOBAL relative to current temperature °C
T_REL_LOCAL Relative to AKO model temperature °C
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12. Thermal Resistance
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13. Self-Heating Effects Id (A) Vd,ext = Vd + Id*RS
348K < TNOM < 300K
10 mW
20 mW
30 mW
40 mW
50 mW
60 mW
70 mW
80 mW
Rth = 0 K/W , RS = 0.32 W
Rth = 600 K/W, RS = 1 W
L11 February 22

14. Self-Heating Effects
SPICE models the IS, etc. the same for all power dissipations.
The effect of diode self-heating is to increase the current at all voltages.
In this case, an Rth of 600K/W gave nearly the same simulation as re-setting RS from 1 Ohm to 0.32 Ohm.
The diode Tj is different at all curr.
L11 February 22

15. PiN Diode PiN: Na >> Nint (= N-) & Nint << Nd
Wi = Intrinsic region (metall.) width
Em,P-T = Peak field mag. when xn = Wi
Vbi = fi = Vtln(NaNd/ni2)
Vbi,int = fi,int = Vtln(NaNint/ni2)
VHL = Vtln(Nd/Nint), the offset at N+N-
Vbi = Vbi,int + VHL
VPT = applied voltage when xn = Wi
L11 February 22

16. PiN Diode Depletion Fields
Normalized Position, x’ = x/Wi
Normalized Field, E/Em,P-T
dx’p
dx’n
x’n
-x’p
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17. PiN Diode Depletion Conditions
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18. CV data and N(x) calculation
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19. Estimating Junction Capacitance Parameters
Following L29 – EE 5340 Fall 2003
If CJ = CJO {1 – Va/VJ}-M
Define y  {d[ln(CJ)]/dV}-1
A plot of
y = yi vs. Va = vi has
slope = -1/M, and
intercept = VJ/MF
L11 February 22

20. Derivatives Defined
The central derivative is defined as (following Lecture 14 and 11)
yi,Central = (vi+1 – vi-1)/(lnCi+1 – lnCi-1),
with vi = (vi+1 + vi-1)/2 Equation A1.1
The Forward derivative (as applied to the theory in L11 and L14) is defined in this case as
yi,Forward = (vi+1 – vi)/(lnCi+1 – lnCi),
with vi,eff = (vi+1 + vi-1)/2 Equation A1.2
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21. Data calculations
Table A1.1. Calculations of yi and vi for the Central and Forward derivatives for the data in Table 1. The yi and vi are defined in Equations A1.1 and A1.2.
L11 February 22

22. y vs. Va plots
Figure A1.3. The yi and vi values from the theory in L11 and L14 with associa-ted trend lines and slope, intercept and R^2 values.
L11 February 22

23. Comments on the data interpretation
It is clear the Central derivative gives the more reliable data as the R^2 value is larger.
M is the reciprocal of the magnitude of the slope obtained by a least squares fit (linear) plot of yi vs. Vi
VJ is the horizontal axis intercept (computed as the vertical axis intercept divided by the slope)
Cj0 is the vertical axis intercept of a least squares fit of Cj-1/M vs. V (must use the value of V for which the Cj was computed).
The computations will be shown later.
The results of plotting Cj-1/M vs. V for the M value quoted below are shown in Figure A1.4
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24. Calculating the parameters
(the data were generated using M = 0.389, thus we have a 0.77% error).
VJ = yi(vi=0)/slope =1.6326/ = 0.640
(the data were generated using fi = 0.648, thus we have a 1.24% error).
Cj0 = 1.539E30^-.392 = pF
(the data were generated using Cj0 = 1.68 pF, thus we have a 12.6% error)
L11 February 22

25. Linearized C-V plot
Figure A1.4. A plot of the data for Cj^-1/M vs. Va using the M value determined for this data (M = 0.392).
L11 February 22

26. Additional Project 1 Actions
What forward voltage range actually fits the standard CV model? Hint: this will be for Va > VPT.
What auxiliary circuit would you add in order to model the diode for operation at Va < VPT?
L11 February 22

27. 2/24 and 3/1 class Project workday on 2/24 – no class
Meet on 3/1 in 212 ELB
Be sure you have a gamma account and can access iccap. If problems, send questions to
We will start using iccap and have a demonstration.
Check project web page for updates
L11 February 22

28. References
1 OrCAD PSpice A/D Manual, Version 9.1, November, 1999, OrCAD, Inc.
2 Semiconductor Device Modeling with SPICE, 2nd ed., by Massobrio and Antognetti, McGraw Hill, NY, 1993.
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