3.6 DLTS signal standards database (DLTS)

 

Starting from version 3.3 of the main program it is possible to compare the measured conventional and Laplace DLTS spectra with the DLTS signal standards gathered in a dedicated data base. In this data base there are results of high-quality and reliable DLTS measurements for a number of point defects for which microscopic structure has been unambiguously proven or defects for which the structure is still debated, however, the technological conditions for their appearance are very well established. In the Laplace system this data base is called the Master data base. The individual entries in the Master data base have been recommended by experts in the DLTS measurements. The content of the Master data base can be merged with any number of other data bases containing the same type of information but coming from different sources, in a future e.g. user own measurements. In the version 3.3 of the main program only the data base containing a choice of entries provided with the version 3.5 of the TrapView© software can be merged. This merge is optional and can be disabled on the Customise form. The result of this merging procedure is another data base which will be called the temporary data base. The content of the Master data base can be also viewed and some results compared to its entries via the Laplace web page http://www.laplacedlts.eu.

 

 The window presenting the content of the temporary data base is opened by pressing this button either on the Laplace or conventional DLTS window. When this button is pressed for the first time the temporary data base is build and a tree view presenting it contents is shown. The first level of the tree view is a material. The second level is a defect. The defect may be presented as a short description, when the entry belongs to the Master data base, or as a code/identifier for the TrapView© entries. Gathering information from and using the temporary data base is based on a similar concept as the experimental data base, i.e. user has to form sets of entries. Clicking an entry adds the first item to a set.  This determines set type: on the tree view all entries from other materials are disabled; entries from the chosen material but representing emission from the opposite carrier are also disabled. For example, if an entry representing the electron emission signal in silicon is chosen then all entries corresponding the electron emission in the n- or p-type silicon are enabled, and all entries relating to the hole emission in silicon and all entries from other materials are disabled.

Clicking the right mouse button opens a context menu with details of this entry and with a web link to the reference describing the given defect and the corresponding DLTS signal. The same information can be found on the central panel. Left-clicking any enabled tree view defect entry adds corresponding defect entry to the set list in the central panel. The defect description is display at the bottom of the panel. Buttons in the central panel of the window allow manipulating entries within the set, and then saving the set with chosen name and optional comment when the choice is completed. It is recommended to save the set for later use before leaving this window.  

 

On the graph in the right panel each selected defect is depicted as two points connected with a line. These are two-point Arrhenius plots for the DLTS signal. Individual entries in the defect databases are stored in a form of two pairs of values of the emission rate and corresponding temperature. These values are used to form the Arrhenius plot for the given defect DLTS signal. They represent a range of temperatures (or emission rates) for which given DLTS signal has been measured and analysed. When any of the end points of the graph is clicked then the corresponding entry on the central panel list is high-lighted and corresponding defect data in the bottom description box is displayed.

These range values, as well as other detailed defect data, can be inspected on LaplaceDLTS System web page (http://www.laplacedlts.eu). For defects gathered in the TrapView© database the temperature range values are in general not known hence temperatures corresponding to the emission rates of 1000 and 1s^-1 has been arbitrary taken.

 

 After choosing standard DLTS signals for comparison with ones own measurement one can close defect selection window and return to the measurement window. Comparison of the chosen signals with own measurements are made by opening text box (press this button). The way the data in this text box is presented depends on from which measurement window this panel has been opened. If it is the conventional DLTS measurement then on top of the box there is the temperature range for which the current spectrum is drawn. Below there is a list of chosen defects with temperatures at which the conventional DLTS peak should appear for the currently used rate window. Usually, the list is organised into three groups: the peaks which should appear at temperatures lower than the lowest temperature on the spectrum, the peaks on the spectrum, and the peaks at temperatures higher than the highest spectrum temperature. If this text box is opened from the Laplace DLTS window then the chosen signal presentation is organised in a similar way but this time according to the values of the defect and current spectrum emission rates at the current temperature.