Some Popular Options
Current Transient Spectroscopy (CTS)
Detects and amplifies current transients. Useful for characterizing samples with vanishingly small variations in capacitance (such as semi-insulating materials). Trap filling can be either by bias changes or optical excitation. Also used in studying traps of FET devices by pulsing the gate and detecting changes in the channel conductance.
Charge Transient Spectroscopy (QTS)
Integration of the current transient allows one to measure trapped charge. Advantages of this method are a very fast response time, extraordinary sensitivity and applications to insulating materials. Unlike CTS, the interpretation of QTS spectra does not have to take into account the relation between spectral amplitudes and the corresponding rate windows.
Isothermal Transient Spectroscopy (ITS)
This accessory allows one to digitize transients over a wide time range, generate a running average to reduce noise and store the raw data for later numerical analysis. The latter could be a specialized method chosen by the user or one of the many routines comprising this package. These include integral transforms for creating isothermal DLTS spectra, i.e. plots of trap concentration vs decay time. The ITS method applies to capacitance, current or charge measurements. It is useful for studying materials which cannot tolerate large temperature ranges (such as organic semiconductors), for investigating the influence of electric fields on trap emission and for resolving closely spaced decay times.
Photo-Induced Transient Spectroscopy (PITS)
Light can be used to create electron-hole pairs for minority carrier injection in conductive devices as well as to create ehp's in high resistivity materials where low free carrier levels preclude trap detection. Our PITS option involves exposing the sample to repetitive pulses of focused light together with monitoring the resultant dynamic signal changes (capacitance, current or charge). The instrumentation provides a wide range of pulse widths and wavelengths. Light sources are laser diodes and high power LEDs which furnish both above- and below-bandgap energies. Optical intensity is regulated via a pulsed current source.
Constant Capacitance DLTS (CCDLTS)
For analysis of samples where detrapping is accompanied by a significant change in depletion width (high trap concentrations, thin films, multilayered structures, MOS devices, etc.). Following the filling pulse, a fast responding feedback loop forces the depletion width (and therefore the capacitance) to remain constant during the relaxation process. The bias voltage required to maintain this condition is an exponential transient which is processed by the Main Unit correlators.
Auxiliary Correlators
These additional correlators, together with the two correlators of the Main Unit, allow simultaneous recording of spectra at four or more rate windows. With this feature, activation energy plots can often be obtained from a single temperature sweep. Also useful for rapid survey experiments which reveal in a single run trap levels with emission times ranging from 80 microseconds to 400 milliseconds.
Fast Pulse Interface
For applying fast filling pulses using an external pulse generator supplied by the client. Useful for precise determination of capture cross sections with values so large that very small pulses are required to achieve non-saturating conditions. Also allows application of large bias voltages (200VDC) for trap depth profiling of wide bandgap materials.