Characterization of Deep-Level Defects in Semi-Insulating GaAs and InP by Photoinduced Transient Spectroscopy (PITS)
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CHARACTERIZATION OF DEEP-LEVEL DEFECTS IN SEMI-INSULATING GaAs AND InP BY PHOTOINDUCED TRANSIENT SPECTROSCOPY (PITS) PAWEL KAMINSKI
Institute of Electronic Materials Technology , ul.Konstruktorska 8 ,02-673 Warsaw ,Poland ABSTRACT Deep states in semi-insulating (SI) materials :GaAs:Cr ,undoped GaAs and InP:Fe are investigated by Photoinduced Transient Spectroscopy (PITS) .The relationship between the Hall mobility in undoped SI GaAs and occurrence of the EL2-related peak in the PITS spectrum is shown. INTRODUCTION GaAs and InP are
(SI)
Semi-insulating for manufacturing
materials
substrate
quali-
high speed electronic devices .However,
strongly
terms of device performance is
ty of these materials in affected by deep-level
impurities and native defects.So,monito-
ring of deep states in
SI GaAs and SI
importance. Because
(DLTS) often TS)
is
to
,relies
[1,2]
as
the photocurrent
while
the
is
is
given by
.The
time
this
study
function
related to the change in
(PI
pulse and ana-
variation
of
temperature
of
the
trap
excess
occupancy
11] (1)
n(t) = NTTnenexp(-ent) where NT is
in
Spectrosccpy
by optical
as a
transient
off
electron concentration
Transient
the traps
on filling
lysing
light
Deep Level Spectroscopy
The technique employed
Photoinduced
and
electri-
the traps by change in
capacitance-mode
not applicable.
referred
of the material
of the high resistivity
hence the difficulty of filling cal bias ,conventional
of great practical
InP is
the trap concentration,
Tn
is
electron lifetime and
e n is the thermal emission rate for electrons. dependence of e n is given by [2) en
T
-1
=
The temperature
n2 rTexp(-E /kT)
where k is Boltzmann's constant ,T is the absolute temperature crossis the activation energy ,a is the apparent capture E a
n
-section for electrons and 2- is material constant (for GaAs rn= n -211-2 -1 20 ). For hole traps, the value of material cm-K-s 2.0 x 10 because of the difference differs from that of r constant y Mat. Res. Soc. Symp. Proc. Vol. 163. 1990 Materials Research Society
76
between the effective mass values for electrons 21 cm-2K-2s-1). = 18X10 Gs =p 1.8 x 1 Gags
This paper is technique ting
for
III-V
holes
aimed at showing the potentialities of
characterization grown in
compounds
were obtained by processing using
and
the double-gated
deep
states
integrator
of PITS
semi-insula-
various conditions.
The spectra
transient current
the photo-induced
boxcar
in
(for
similarly
as in
DLTS
technique. RESULTS AND DISCUSSION direction by
The GaAs and InP crystals were grown in liquid-encapsulated
of Cr-doped
The resistivity was 5 x 10 a cm crystal
bility
(LEC)
Czochralski
probably due to its
The chromium concentration absorption
,
was 3 x
10
16
.
GaAs samples,measured
and Hall mobility about
was pulled from the quartz
is
method
1500 cm 2/Vs
crucible,the
by optical
Figure 1 shows the PITS spectrum
cm-.
for the Cr-doped GaAs samples
and
the
activation
energies
TC5 0.52eV
