3.5 The conventional DLTS measurement (DLTS)
In
this version of the program there are three different routines enabling to
perform the conventional DLTS measurement. The first one (TrapView ver. 4.0) basically copies the idea
of the TrapView program where a user can perform multiple temperature scans with
different hardware setting, and during each scan two spectra with different rate
windows are measured. The other two use single temperature scan during which
sufficient information is acquired to construct a reliable Arrhenius plot of
defects observed. The conventional DLTS measurement utility is accessed from the
Main form by pressing the Conventional DLTS button or from the Measurements
menu. The conventional DLTS measurement in any of the three routines can give a
quick overview of the defect contents in the sample, however it is advised to
perform more elaborated DLTS measurements like the carrier capture process, the
emission process electric field dependence, the minority carrier recombination,
etc, in the Laplace DLTS mode, in particularly, with a use of scripts.
The measurement of the DLTS signal for all three routines is based on the same concept. Namely, after the voltage pulse (or sequence of pulses) is to the sample applied (with parameters set on the Generator tab) the capacitance transient is measured with the preset acquisition parameters. Then the transient is analysed in a way specific to each of the measurement routine and the conventional DLTS signal is calculated. The differences in these analysis processes for each routine are described in the following chapters. The acquisition process is realised during the temperature ramping. The ramp rate is set on the Temperature tab, and the current and average ramp rate are calculated and displayed on the status bar at the bottom of the window. The ramp averaging time is set on the General tab. On the status bar there is the Temperature interval parameter showing how much the temperature has changed during one complete transient measurement and processing procedure, and consequently, what is the current temperature distance between subsequent points on the conventional DLTS spectrum. It is a question of a user personal experience how big this parameter should be, however, it is advised to keep it below 1K for good quality measurements. The temperature interval can be changed by reducing the temperature ramp value (even while the measurement is running) or by reducing the Single transient measurement time. This parameter represents the number of transient averagings used for measurement of each transient. By reducing this parameter one can obviously speed up the measurement process, however in the same time the measurement noise level increases.
3.5.1 TrapView version 4.0