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FAQ's to Physics

FAQ's to Install

• Are there new options in the version 4.0?
  Yes, in the version 4.0 are three new software options which are not included in the standard package:
  C(T): Static capacitance or current can be measured in dependence of temperature. This means temperature dependent C/V and I/V curves, Richardosn plot, CR(T), CP(T), TSC, TSCAP. For the trap concentration here is a Ns(T) correction possible.
  Data bank: Evaluation values and measurement reports can be saved in a DBASE data bank, also called report file.
  Routine module: This makes measurement and evaluation more easier. It combines different modules.

• How can I take the evaluated values in the Arrhenius plot as simulation data?
  Type in the Arrhenius plot the function key Alt-F3 and then you get an input window. For the question to apply the evaluation datas as simulation parameters you need user class 5 or higher.
• In the ITS module I find the menu point "Trap profile with difference". What does the difference mean?
  Trap profile with difference means that from two measurements with different reverse bias the difference will be used for one point in the trap profile. If you do this point by point you get the trap profile.
• What means in ITS the "transient value"?
  The transient value define the number of data point measured during one transient. The normal numbers are 512 for a tempscan or single transient. For ITS transients during period width scans this number is too high and not well because fix recovery time of bridge. Here the number of data point per transient is reduced to 64.
• At the ITS plot we sometimes see a peak at a period width of 100us, but in the ITS evaluation we cannot see this peak!
  In the ITS plot is normally Tw the x-axis (select in 4.4.1). The plot with Tw as x-axis is only valid if Tw/t0=constant. That is for small Tw not possible because Boonton recovery time. In the case of Tw=100us, Tw is a factor of 2 smaller than t0! So it could be that you see in the Tw-plot at short Tw a maximum. This is not a true maximum, it comes from the changing of Tw/t0. In the ITS evaluation you see the corrected plot, that means tau as x-axis and a correction for the y-axis that recalculate to a constant ratio of Tw/t0. This evaluation plot should be the true plot, but problems here are possible with very small period widths.
• Why some times stops the I/V curve measurement?
  One reason could be the maximal current. Check this input. An other explaination could be the voltage interval. Try it with a smaller one.
• I can not work with more than four tempscan files?
  Set BUFFERS=20 in the file CONFIG.SYS
• Why we get some times memory problems and post mortem dumps?
  The memory error and the post mortem dump are coming from the same proble. The free memory in DOS for the executable file is too small. It has to be more than 580 KByte, and an EMM memory has to be installed. You have to change the CONFIG.SYS and the AUTOEXEC.BAT file. Load high all drivers and resident programs. You can find an example for these two files incl. explaination in \dlts\dltfs\install\default. If the memory is large enought there will be no error. You avoid memory problems while running the DLTS program in the DOS box of Windows 95/98.
• How can I see how much memory is free?
  You can see the biggest free memory block (not the total free memory) in every menu and in the plot status line by Alt-M.
• If I change at the tempscan evaluation the sample area and then load a new file, the area will be overwritten?
  The sample area is a part of sample and so it it will be saved at the data header. If you read a stored data file then the sample area will also readed and set new. For the next measurement the program asks you if you want to keep the old are or the readed area. In the init file is only saved the default value for the measurement bit not for readed data. To avoid such problems and you have the wrong area save on your files please load the file, change the sample params and save the file again with the same file name. You have to do it for all files!
• Should I work always in user class 6?
  Please use only user class 4. That is the normal expert class. User class 5 is only in some special cases helpfull. User class 6 is more for testing. It is much easier to work with the program in user class 4 or less!
• Although I get a plot for NT I get the error message "no plot data" for the excact trap concentration?
  The problem with the exact NT-calculation can be a physcial problem. For this calculation you need the shallow concentration and the space charge region, that means the capacitance. You have to calculate Ns and to measure the reverse bias and the pulse capacitance exact. Have a look to the equations, you find it at the global help or at the FAQ. The pulse capacitance is normally only calculated. Sometimes it is not possible because high NT, not good Schottky diode, temperature depending Ns and so on. Then you get bad results for the space charge region and so no plot points.
• How can I save/read init files?
  You should save init files during finishing the program. You can save it as hot file and start it with the hot file, or you can define the extension (buffer / save init file, extension input). At program start, you can then define the extension, and the defined parameter set will be loaded.
• How can I save a special tempscan init file?
  First you have to define your measurement tasc in 5.2 Tempscan with manual parameters (5.2.2, 5.2.3, 5.2.4, 5.2.1 break before starting (in save) or do the measurement and follow the steps afterwards). Then save the user definable init file in 5.2.5.5. Following options are possible: (open input: 'mode for saving init file'): 1. special user init file temp_52.I5A If you save your measurement file under this name, you can run the measurement tasc easily with 5.1.5.2 (Tempscan with routine params, User routine measure, measurement with user init file). You then have not to define the measurement file name (it is predefined). 2. Temp_??.I5B This will change (for the customer) the definition of our standard and special routine measurement parameter sets. ?? means the last 2 numbers of our keys e.g. 11 means 5.1.1.1 (TW1=const, fast measum.) 21 means special routine measure single level no superposition) and so on. 3. *.I5? Here you can give a free name for your measurement tasc. You can run the measurement tasc by 5.1.5.3 or 5.1.5.4. You have to load this tasc before you can start, it will automatically show the input of file name 5.1.5.3 or a list of available measurement tascs 5.1.5.4.
• What mean the different pulse modes?
  There are two independant pulses. The first one, if selected (see below), is called injection puls. You can set the pulse widths and, if the first one is the electrical one, also the voltage for the pulse. 1) without pulse 2) normal: one electrical pulse. 3) double pulse: You can set the params of both electrical pulses independently. The first puls is named injection puls. 4) optical: Will give only an optical pulse to the sample. The pulse width is given in "rev bias and pulse". The reverse bias voltage is kept constant. 5) electrical & optical: will give at the same time an optical pulse and an electrical. 6) electrical, optical: give an electrical pulse first (this is named the injection puls) and an optical pulse direct after that. Both can have different pulse widths. 7) optical, electrical: gives first an optical pulse ane then an electrical. As above both pulse widths can be set independently.
• We want to make tempscans by different temperature steps for different temperature regions. It is possible?
  For the temperature steps you can select an "external file" in the input window of temp params. The temperature step you can define in an ASCII text file. Use for this option NotePad or WordPad (here only text file mode) and define the temperatures in Kelvin. The first temperature must be in line 1, the second in line 2 and so on. For example create the file TempStep.TXT with 6 lines( 100.0, 101.0, 102.0, 110.0, 120.0, 140.0). Save this file in your init directory, e.g DLTS\WORK\INIT. In the program use this file for external temperatures. Set the temperature start and end temperature between the min and max temperatures of the file.
• Sometimes I see negative transients?
  Negative transients come either really from the sample or a effect of wrong measurement conditions. The reasons for the last are to low capacitance range, to long recovery time, to high leakage current, bad Schottky diode, short circut to ground and so on. Check the effect by different rverse bias, pulse voltages, pulse width and period widths. You can also use the ITS measurement with automatic change of the voltages. If you have measured in range 1 of the Boonton meter, try it in range 2. A reverse bias change can help, but not solve the problem. Check the noise spectrum (your sample attached, not a reference sample). If it gives you a very high 50 Hz (or other) signal it can be the there is a (temperature dependant) short circut to ground.
• While calibration procedures we get the messages "Range for zero definition test : 2" and "Min. Capacitance for main calibration : 0.003". Why happen error and what is mean 0.003?
  The calibration procedure is not calibrating the Boonton meter. The four steps of the calibration procedure are: 1. It measures the offset capacitances of the Boonton meter in the 4 different ranges compared to the defined (normaly range 2) one and save in a list. The message "Range for ....: 2" is a user information, and no error message. "Min. Capacitance...: 0.003" gives the software accepts it as zero. It is needed for the compensation routine. 2. It measures the compensation capacitances that are used for compensating the rev. bias capacitance. 3. It measures all offset voltages of the measurement equipment. 4. It compensates cable capacitances. All these values are used for calculation the correct capacitance out of the measured signal and for a correct sample capacitance compensation. So it is absolutely necessary to do a calibration. The compensation should be redone always if cryostat has changed, cables to the sample, or the system had not worked for a week or more. The "zero" is O.K. if the reading is below +/-0.5 pF. A better one is not needed. If you measure C/V the Boonton is measureing in Range 3 and 2, because the capacitance is normally app. 300pF to 50pF and this Zero error could be neglected than. For transient measurements the zero is not used. Transient are measured relatively to a compensation capacitance and not absolutely. You will get the full resolution for the amplitude, and this is what is important for DLTS. To show the zero stability you can use "test for contact" and select range 1 for the Boonton meter. The reading should be a little be away from 0 reading, but stable. You can than adjust again manually with the zero knob at the Boonton the zero reading. This should give a stable 0.01 or so. But it will not make a difference in system accurancy, this is good in any case.
• Why sometimes appears a compensation error?
  A compensation error appears always, if a capacitance cannot be compensated, due to different reasons. If there is no sample, the compensation definitly does not work. Other reasons are a bad Ohmic contact of sample, high leakage current, to low bridge range or to high "Min. compensating capacitance".
• When we plot more than one DLTS curve to the same picture in the presentation plot program we see only the last plotted curve. The other ones are somehow hidden.
  For comparing DLTS curves in the presentation plot program plot all curves in one layer (Take over current data: additional curve/array). Then you see all curves. If you use manually more than one layer, you have to change the layer size, so that the layers dont overlap or one layer is inside of an other layer. You can change the layer/boarder size by F1, see full info by Alt-F2.