ATLAS常见问题解答.docx

1、ATLAS常见问题解答ATLAS常见问题解答Q1The ATLAS Users manual, Vol. II said that the conversion from resistivity to carrier concentration is base on table, which is derived from Arora mobility model. Could you inform me in more detail about those tables and the conversion tool (if there is one)?A1The conversion of

2、 resistivity to carrier concentration in silicon using the RESISTI parameter in the DOPING statement is base on the following equation: Carrier Concentration = 1 / (R * q * u) (in cm-3) where R is the resistivity (in ohm-cm); q is the charge; and u is the mobility (in cm2/. In ATLAS, Arora mobility

3、is used for computing the carrier concentration. The computation of the resistivity to carrier concentration in Silicon for both N-type and p-type carrier are as shown in the figure below.Q2Part I: How can I simulate the short circuit current, Isc and open voltage, Voc of a Solar Cell in ATLAS? A2Th

4、e short circuit current, Isc can be extracted from the IV curve when the voltage is 0 while the open circuit voltage can be extracted from the IV curve when the current 0. The figure below shows the location of the Isc and Voc values. The commands used to extract both values are as follows: extract

5、init inf= # Extract Short Circuit Current extract name=short_circuit_current from curve(v.cathode,i.cathode) where =0 # Extract Open Circuit Voltage extract name=open_circuit_voltage from curve(v.cathode,i.cathode) where =0Q3Part II: How can I include a variable load resistance (external load) into

6、the simulation program and simulate the IV characteristics of a Solar Cell? A3There are 2 methods of adding an external resistance to a device: i. The first method is to add a lump element; andii. The second method is to add a distributed contact resistance. The first method is to specify the value

7、of the resistance in the RESISTANCE option of the CONTACT statement. However, this method is only applicable for planar metal-semiconductor surface. The second method is to add a distributed contact resistance, for non-uniform metal-semiconductor surface. For this method, the option was used instead

8、 in the CONTACT statement. Below give an example of how to compute the value. Assuming an external load of 50ohm at the Cathode contact, the (in ohm-cm2) is calculated as follow: = 50 x Cathode_length x cathode_width = 50 x 140 um x 1um = 7e-5 ohm-cm2 Then, you need to specify the CONTACT statement

9、as below: CONTACT NAME=CATHODE =7E-5 Below shows the simulated IV characteristics of a Solar Cell with and without a 50 ohm external load.To extract the channel length, use the following EXTRACT statement as follows: extract name=junc_source xj silicon =1 = =1 extract name=junc_drain xj silicon =1 =

10、 =2 extract name=Channel Length $junc_drain-$junc_sourceQ4How to extract Ioff in SILVACO TCAD tools?A4Firstly you should know the definition of Idsat and Ioff. When Ioff is defined as the drain current at gate voltage equals to 0v, you can use following statement: Extract name=”Ioff” from curve(v.”g

11、ate”, i.”drain”) where =0 After run this statement, you will get a result which is stored in file .Q5I have finished the simulation of BJT and get the IV curve, but I could find how to display the curve beta vs. base voltage. Is that possible to display such curve?A5Yes, it can. Firstly launch TonyP

12、lot and open the log file which include IV curve. Then, click “tools”- “display” in the menu, select “Function 1” in the “Y Quantities”After that, click button “Functions” which is in the left-bottom. A window will pop up like following:In this window, type in “Collector Current / Base Current” whic

13、h is also showed in above picture ( because beta is defined as beta=Ic/Ib ) Then click “Ok” to finish. Then you will get a curve which x axis is base voltage, and y axis is beta. See follows:Q6How to obtain the Capacitance-Voltage (CV) curve of a MOS capacitor at low frequency?A6In the simulation of

14、 CV curve, SRH model needs to be added to the input deck file. This is because when reverse biasing the MOS capacitor, GENERATION in the depletion region actually dominate over RECOMBINATION, as the carrier concentrations are less than their thermal equilibrium values; . pn I increases - C increases

15、. The generation rate in the depletion region, G = ni/2T, where T is the lifetime of the effective lifetime, . T = (Tn + Tp)/2. Therefore, G is inversely proportional to T = The shorter the lifetime T, the greater the generation rate G = greater I = greater C. Hence it is necessary to add the SRH mo

16、del and also reduce the effective lifetime of the carriers in the bulk for simulating the CV curve. This can be done by adding the following statements: material taun0=1e-11 taup0=1e-11 model srh Below shows the simulated Capacitance-Voltage (CV) curve of a MOS capacitor at high and low frequency.Q7

17、The MOS capacitor being a two terminal device, the two capacitances should be identical in magnitude. Simulation however shows them to be a few orders of magnitude different. Our theoretical estimation tell us that Csubstrate-gate between 8e-16 to Farad is correct. Cgate-substrate is between and F i

18、s confusing to us.A7Atlas performs a small signal ac analysis as described in the paper by Laux Ref. 74 of Atlas vol II Bibliography. According to ref. 46, the admittance matrix is defined as: Y(ij) = I(i) / V(j) where I(i) and V(j) are the phasor terminal current and voltage respectively. The real

19、part and imaginary part of the admittance matrix determine the conductance matrix G and the capacitance matrix C respectively. In Atlas, it is these conductance and capacitance that are being output. For instance, the capacitance matrix C is calculated as follows: Imag Y21 = -1*(2*frequency*Cgatesub

20、strate) input port=Gate, output port=Substrate Imag Y12= -1*(2*frequency*Csubstrategate) input port=Substrate, output port=Gate Therefore, the value of Cgatesubstrate does not equal to Csubstrategate.Q8In general, how to solve convergence problem?A8To solve convergence problem, 1) Try the refine you

21、r mesh especially at areas where carriers activity are most prominent such as areas near and at the junction or the Schottky contact, 2) Use a smaller step size . vstep = or even vstep = rather than a large one such as 2V. 3) By default, only Newton method is used. Try to use both the Gummel and New

22、ton Methods in the Method statement. This will cause the solver to start with Gummel iterations and then switch to Newton, if convergence is not achieved. This is a very robust, although more time consuming way of obtaining solutions for any device. 4) Refer to ATLAS Users Manual on Choosing Numeric

23、al Method pp. 2-27 to decide on the most appropriate methods to be used for your device.Q9Can you tell me how to retrieve the default parameters of SiC in the ATLAS?A9The default value of all material can be found in ATLAS Users manual vol. II Appendix B (You should have a pdf format of ATLAS manual

24、 in your silvaco directory: /doc). You may also view it by adding the print option in the Model statement.Q10I notice in Appendix B, Page 21, there lists some optical properties of several semiconductors such as Si, AlAs, GaAs. How about ternary compound semiconductor and quaternary semiconductors,

25、such as InGaAs or InGaAsP?A10All the default complex index of refraction for Si, AlAs, etc are listed in B-21. For those materials which are lack of complex index of refraction, you need to specify the index indicated in pp. 8-11 of ATLAS Users Manual Vol. 1. i. To set single values of Refractive In

26、dex regardless of wavelength, you may use the and parameters of the MATERIAL statement to set the real and imaginary indices of the ternary and quaternary material, region or regions; ii. To set a Wavelength Dependent Refractive Index for multispectral simulations, you need to specify index versus w

27、avelength: a. In a file known as the INDEX file. Note that if you use this method, only linear interpolation from the table in the INDEX file will be used. b. Use the C-INTERPRETER function in which it can returns wavelength dependent real and imaginary indices. Also note that you can add the parame

28、ter to any SOLVE statement to print out the refractive indices being used for that bias step.Q11How to define a new material such as InGaN by using the C-Interpreter?A11It is possible to simulate the user-defined material such as InGaN by using the C-Interpreter. The template file for the C-Interpre

29、ter is as attached. Please save this file in your working directory . C:SILVACOwork. The procedure involves in specifying . the band composition, for user-defined material . InGaN using the C-Interpreter are listed below: 1. In your MATERIAL statement, you need to define: material material=InGaN = w

30、here specifies the name of a file (in this case is containing a C-INTERPRETER function for the specification of temperature and composition dependent band parameter models. 2. Next, open the template file . C_template, using WORDPAD Application. Go to the function and you will see something as shown

31、 below: /* Temperature and composition dependent band parameters* Statement: MATERIAL* Parameter: * Note: This function can only be used with BLAZE.* Arguments:* xcomp composition fraction X* ycomp composition fraction Y* temp temperature (K)* *eg return: band gap (eV)* *chi return: affinity (eV)* *nc