An
important goal in semiconductor technology is the
reduction of intrinsic and process-induced defects in the
crystalline, polycrystalline and amorphous layers which
comprise all semiconductor devices. Defects arising from
impurities, grain boundaries, interfaces, etc. result in
the creation of traps which capture free electrons and holes.
Even at very low concentrations these trapping centers can
dramatically alter device performance.
Deep
Level Transient Spectroscopy is an extremely versatile
technique for the determination of virtually all parameters
associated with traps including density, thermal cross selection,
energy level and spacial profile.
By
monitoring capacitance or current transients produced by
pulsing the semiconductor junction at different temperatures,
a spectrum is generated which exhibits a peak for each deep
level. The height of the peak is proportional to trap density,
its sign allows one to distinguish between minority and
majority traps and the position of the peak on the temperature
axis leads to the determination of the fundamental parameters
governing thermal emission and capture (activation energy
and cross section). Application of the method has led to
the discovery of new phenomena and has provided a unique
tool for the understanding of materials processing for semiconductor
devices.
At
one time the expense and complexity of laboratory assembled
deep level spectrometers limited the use of DLTS to a relatively
small number of specialized research groups. In
response to this situation we developed a low cost, dedicated
DLTS instrument, which contains all the functions necessary
to carry out precise and reliable deep level measurements.
