A low-cost microprocessor-based Deep-Level Transient Spectroscopy (DLTS) system

A microcomputer-based DLTS system is presented, in which the microcomputer functions as a signal averager and controller. The system can detect traps deeper than 0.20 eV from the band edges and 10
³
cm
^-3
less dense than the intentional dopant concentration. The system was applied to the study of deep traps in liquid-phase epitaxy (LPE) grown GaAs and vapor-phase epitaxy (VPE) grown GaAs
_0.75
P
_0.25
light-emitting diodes (LEDs). A deep donor level at
E
_c
-0.70 eV and σ
_n
=1.3×10
^-15
cm
²
was found in the latter which agreed with capacitance-transients experiments done by another investigator. The electric-field strength was seen to inversely affect the electron capture cross section of this level. A minority-carrier trap reported at
E
_v
+0.15 eV was observed but its energy level was not resolved due to its broad DLTS spectrum peak. The GaAs LED exhibited emission from a deep acceptor level at
E
_ν
+0.81 eV and σ
_p
=2.2×10
^-15
cm
²
, σ
_n
=6.8×10
^-22
, and a deep donor level which could not be resolved.