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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