GaAs

Nuclear Instrnments and Methods in Physics Research B37/38 (1989) 352-356 North-Holland, Amsterdam

352

ELECTRON BEAM DOPING OF Si INTO GaAs IN THE OVERLAYER AND THE SANDWICHED SYSTEM OF GaAs/Si/GaAs

Si/SUBSTRATE

GaAs

Takao WADA and Akihiro TAKEDA of Electrical and Computer Engineering, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466, Japan

Department

Si atoms were introduced in (lOO)-oriented undoped semi-insulating GaAs at 50 o C by using an electron-beam doping method t of - 0.5 mm was sandwiched between two wafers of GaAs: GaAs (layer 3)/Si (layer Z)/GaAs (layer 1) (sandwiched array). The surface of layer 3 was irradiated with a fluence of 5 x 10”electrons cmm2 at 7 MeV. After annealing at 800 o C for 20 rnin with a SiO, cap, the 0.6 mm thick GaAs wafers (the layers 1 and 3) converted to p-type, and the peak carrier concentrations at the surfaces of layers 1 and 3, which were in contact with the Si surface, were - 3 X 10” and - 4 X lOI cmm3, respectively. The photoluminescence spectra at 77 K for layers 1 and 3 indicated two dominant peaks, which were attributed to the Si acceptor, Si,,, at 1.48 eV and to the band gap transition at 1.51 eV. In the case of the sandwiched array electron-beam doping was experimentally determined to be more effective than in the case of the two layer array (an overlayer Si/substrate GaAs). from a Si sheet. A Si sheet with a thickness

1. Introduction

of arrays are used. As shown in fig. la, the Si sheet was sandwiched between two wafers of GaAs, that is GaAs

The physical by high energy workers

properties

of semiconductors

irradiated

(layer

electrons

have been

by many

was in contact

[l]. Ion implantation

nological cation

advantages

of electronic

process

devices.

[2]. Electron

to occur

However,

introduced irradiation

of complex

in neutron

conditions

injection

have been directly

methods

of electron

tion

[7] and epitaxy

authors

and

impurity ductor

semiconductor energy In

(2-7

doping

The

EBD

or a vacuum surface

MeV)

which

new oxida-

by one of the employs

an

with the semicon-

evaporated

layer

is bombarded

on the

with

paper

we study

properties

of GaAs

doped

the

electrical

and

with Si by the EBD

of

wafers were

and impurity (lOO)-oriented

grown by liquid

and (lOO)-oriented mensions

accelerator

surface

of layer

3 for

duty

of

- 40 PA cmp2.

During thermal

cycle

and

irradiation,

circulating

cm-2

with a

at 7 MeV from an

with a pulse width of 3.5 t.ts,

Hz

an

average

the samples

water

as shown in fig. lc. After

bath

electron-beam

were put in an iso-

using

a thermoregulator

irradiation,

the GaAs

samples

of layers 1 and 3 for A.111 and of A.11 were annealed 800°C

for 20 min with a SiO,

furnace.

After

luminescence

stripping (PL)

K. A focused

off

cap

the

measurements

800 mW,

used as the excitation

3.

5145

at

in a conventional

SiO,

films,

photo-

were performed

A argon

laser

at 77

beam

was

source.

Experimental results

GaAs

samples

tively.

The

mental

B-doped

0168-583X/89/$03.50 Physics

sheets

used in the experi-

undoped

encapsulated

of each sample

(North-Holland

and each In another

with a GaAs

The surfaces

- 5 x 10” electrons

linear

current

p-Si,

semi-insulating

Czochralski respectively.

di-

are shown in fig. 1. Two kinds

0 Elsevier Publishing

Science

Publishers

Division)

B.V.

and broken

spectrum

the most when

a peak

suitable

the following

attributed

at 1.51

eV, a peak

isolated

Si atoms

peak attributed

lines

for the EBD

indicate

and each Lorentzian

to obtain

assumed:

(LEC) The

EBD

PL spectra

of layer 1 for A.111 and of AH,

solid

results,

puted ments

(fig. lb).

Figs. 2a and 2b show typical

2. Experimental procedures

GaAs

(AH))

layer.

high

technique.

The

1) (A.III),

surface

electrons.

the present

optical

[4-61,

technique

in contact

carrier

[3]. Recently

(EBD)

in

(layer

another

a 200

irradia-

reactions

minority

[8,9] were reported

or water,

surface,

of

observed

beam

others.

sheet,

particle

annealing

2)/GaAs

with

A.111 and of the Si sheet for A.11 were irradiated fluence

regions presumed

(layer

the Si sheet was in contact

electron

and heavy-charged

semiconductors

array,

(Si/GaAs,

is accompanied

avoids the complication

of defect

3)/Si

by the implantation

damage

tion. The enhancements under

of tech-

in the fabri-

it is well known

in semiconductors

damage

of the generation

offers a number

which are important

that ion implantation by radiation

studied

shaped

to the band

attributed

to silicon

on As site Si,, to the residual

peak

agreement emission

respec-

the expericom-

for

the

peaks

are

gap transition acceptor

with

at 1.48 eV [lo]

and a

copper

in Ga site Cu,,

T. Wada, A. Take-da / Electron beam doping of Si into Ga.As

A.IB

a High

energy

electron ~=5X10’7e/crn2)

(E=7MeV

( layer 3) Si ( layer 2) GaAs ( layer ,l)

+6mm---*/ in running

water

b

A.11 High

energy

( E=7MeV

electron @= 5x 1017 elcm2)

353

A.111 and A.11 are shown by the solid and broken lines, respectively, in fig. 3 as a function of depth from the front and back surfaces of the GaAs. They were measured with an electrochemical C-V profiler. The solid lines show the profiles to a depth of 35 urn from the front and back surfaces of layer 1 for A.111 after annealing at 800°C for 20 min. Large buildups of carrier concentrations at both the front and back surfaces of GaAs layer 1 were observed. The hole concentrations near the front and the back surfaces and in the center of layer 1 wafer for A.111 are - 4 X lo”, - 3 X 10” and - 1.5 X 10” cmm3, respectively. The broken line indicates the profile in a depth x range of O-5 urn from the front surface of the GaAs sample for A.11 after annealing at 800 o C for 20 min. The carrier profiles could not be observed near the back surface for several samples of A.11 even after annealing at 700, 800 and 900 o C for 20 min. This may be caused by lattice imperfections induced in the doping process. The hole concentration near the front surface of the sample for A.11 is - 1.5 x 10” cme3, which is lower than that ‘for the sample for A.111. The profile for A.11 contains a dip at x = 2.4 urn, which may be due to the effect of complex defects.

a

EBD-&As(layerl)

A in running

water

C Llnac

\ Anneal :BOO”C, 20min

EBD-GaAs

II

b

A.11 +

Current monitor

SaGpIe

Fig. 1. Schematic diagram for the experiments of the sandwiched array of GaAs/Si/GaAs (A.111) (a), the array of overlayer Si/substrate GaAs (A.11) (b), and schematic diagram of electron irradiation at 50 o C (c).

at 1.36 eV [ll]. The PL spectra for layer 1 of A.111 indicated a clear peak which is attributed to the Si acceptors (Si,,). On the other hand, in the case of A.11 the Si As peak was rather unclear, The ratio of the emission intensity for the Si-acceptor of GaAs (layer 1) for A.111 to that of GaAs for A.11 was nearly 4 to 1. The hole concentration profiles in the GaAs substrate of

Anneal: 8oO”C, 20min

Photon

Energy

(eV)

Fig. 2. Typical photoluminescence spectra for the EBD GaAs samples of layers 1 for A.111 (a) and of Si/GaAs (A.11) (b) after annealing at 800 o C for 20 min. IV. ION IMPLANTATION

354

T. Wade, A. Takedu / Electron beam doping of% into GuAs

,<

10ZO:

1

A.@

. EBD-GaAs

-

-

lOI9 :

--I--

% U

layer1 ( A.lll ) ’ &As ( A.ll ) :

Back Surface Front

.k

.

Ann~~:~~OC,ZOmin

Surface

tote : P -we

1o15 .

*

' to

)

' 20

'

t

-

Front Surface (x=0)

'

'

30

'is

30

Depth in Substrate

10

20

f Back Surface (x=t)

(pm)

Fig. 3. Carrier concentration profiles in layer 1 for A.111 and in the GaAs samples for A.11 as a function of depth from both the front and back surfaces. They were measured with an electrochemical C-V profiler.

It

10ZO.

. EBD-GaAs(layer31

1 Bat k Surface (x=t 1

A.lU GaAs

6

lOI :

Front Surface

E 2 4, ;;( I_

(x=0

1

layer3

Si

layer2

IZZI GaAs

layer1

Anneal:8OO”C, 20min .

1018 r

p-type

I 10

lOI

I Front Surface (x=01 Fig. 4. Carrier concentration

L

I 20

I

I 30 *Depth

*

1::’

’

’ . ’ 30 20 in Substrate ( pm 1

g

’ 10

*

t

Bat k Surface (x=t f

profile in layer 3 for A.111 as a function of depth from both the front and back surfaces. This was measured with an electrochemical C-V profiler.

of Si into &As

T. Wada, A. Takeda / Electron beam doping Fig. 4 indicates depth

the carrier

of 35 urn from

concentration

the front

layer 3 for A.111. This also indicates profile.

After

thick

GaAs

verted

800 o C annealing samples

to p-type.

front surface

of layers

through tions

of

depending

conditions,

the

on

in the section

the sample

would

give rise to a U-shaped

and 4 has been observed

concentrations C-V

irradiation

mea-

unstable annealing

by lattice

imperfec-

as will be men-

4. On the contrary,

for A.111, good reproducibility

Torr).

ranges

are about

of

the

Thus,

the impurity

allow

the

without

The production irradiation EBD

layer

semiconductors case

to

a significant

rate of defects

are about diffusion

The

rate

(EHPs)

of

loss

EHP-

1 dE

d+

z dx

dt

atoms

G of

of the

10”

plasma

and

would EHPs

electrons,

and some ions in layers level

is near

diffusion external tron-hole The properly

holes,

in-

level,

of the order

during

of

the irradiation, ionization

Si impurities,

vacancies

occur

when the Fermi

the ionization-enhanced

can be operative

by an irradiation

U-shaped

diffusion

by taking

account

mechanism

diffusion

D,

is much

D,.

The recoil

under an

that creates

the surface

profile

may

be

of the surface

elec-

than

impurities

that

explained

diffusion

[6]. The diffusivity larger

concentration

nearly

equal

of the volume

diffuse

at the back

to that

and

of the surface very fast on

from the front to the back surfaces,

impurity

array

III

(10~6-10-5

would not be largely

layers

formed

by reaction

suggested

that

a mechanism

plasma-grown

for EBD

was quite array

plausible

(A.II),

the

Si sheet

and

during

the

electron

irradiation.

sheet,

the enhanced-diffusions

tion

The

lattice

for electrical

the

GaAs

crystal

imperfection

couples

samples,

which

Even

the

of Ga and

and optical

in

As atoms

causes

properties

not only the diffusion

a degrada-

of GaAs.

of Si atoms

but also that of As and Ga atoms layer

2 and into

accomplished atom

migration

portant

role

migration

layer through

from layer 2,

effective

EBD

may be

array, and it is thought

process.

will play A study

an imon atom

in the Si sheet is now in progress.

of of

the

Semiconductor

for

their

Scientific Special Physics

of Education,

H. Masuda

Industrial help

of the samples.

by the for

to M. Takeda,

Government

Nagoya

61114002 Ministry

On may

from layer 3 through

the Si sheet

in the doping

We are grateful

in part

1. More

by the sandwiched

Si

may

the other hand, in the case of A.111, the irradiation generate

to on

[7]. In the

GaAs

due to diffusion

between

also occur.

similar

oxidation

in connection

and Science

Inwith

This work was supported

Research Project

and K.

Research

Grant-in-Aid

Research Electronics”,

on

No. “Alloy

from

the

and Culture.

at 7 MeV and 50 o C

1, 2 and 3 [7]. Since alternative

mechanisms

diffusion

becomes

= 3 X 102’

radiation

pairs [14].

the kickout

the

GE,,

The

density

of a defect

excitation

[15]. The

by a full or partial

the defect

(IED)

cme2 Thus

may be produced

in

s-l.

defect

in the sample.

changes

of EHP (e in Si and

result

cmp3

a uniform

charge-state

pairs

beam can

- 4.6 eV, respectively)

of 5 X 1017 electrons

includes

electron

for

vacuum

process

or oxide

two layer

bombardment

irradiation

cmp3

that

electron-hole

’

= 5 x 10”

fluence

in GaAs.

in

occur

stitute

is

may produce

of

but also

obtained

from the stoichiometry

Yasuda

GaAs electron

mechanism

[14]:

c is the energy for formation

and

the

energy.

of Si atoms,

where

- 3.23

in kinetic

[13]. The

of impurity

as follows

to

into

in Si for 7 MeV electron

8 cm -’

generation

[12].

thin

penetrate

per unit time by an incident

be estimated

at 7 MeV in Si

is sufficiently

electrons

is not only the recoil process

enhanced

G

sheet

irradiating

substrate

of electrons

the EBD

conventional

was obtained.

15 and 5.65 mm, respectively

were

irradiated

It was also that

[18]

The extrapolated

In the

with water.

in the case of

4. Discussion

profile.

length as shown in figs. 3

[6].

results

by water

deviates

and GaAs

PL

Therefore,

affected

diffusion

a large diffusion

(GaAs/Zn/GaAs)

and

process

Similar

at the

- 4 X 1017 cmp3.

electrochemical

in the doping

carrier

Then the impurities diffuse into the specimen from both surfaces through the value of 0,. This diffusion process

1 and 3 for A.111 con-

of A.11 was slightly the

of

case of EBD,

and this may be caused

induced

tioned

a U-shaped

of layer 3 for A.111 was

for the sample

to a

surfaces

for 20 min, the 0.6 mm

The peak carrier

Reproducibility surements

profile

and back

355

of the front

and thus

surface one,

N,_, N,=,.

References 111 J.W. Corbett, Electron Radiation Damage in Semiconductors and Metals (Academic Press, New York, London, 1966). Solid State 121 J.W. Mayer and O.J. Marsh, in: Applied Science, eds. C.J. Kriessman and R. Wolf (Academic Press, New York, 1968). [31 L.C. KimerIing and D.V. Lang, Inst. Phys. Conf. Ser. No. 23 (1975) p. 589. [41 T. Wada, NucI. Instr. and Meth. 182/183 (1981) 131. [51 T. Wada, Proc. 3rd Int. Conf. on Neutron-Transmutation Doped Si (Plenum, New York, London, 1981) p. 447. [cl T. Wada and H. Hada, Phys. Rev. B30 (1984) 3384. [71 T. Wada, Appl. Phys. Lett. 52 (1988) 1056. PI T. Wada and Y. Maeda, Appl. Phys. Lett. 51 (1987) 2130. [91 T. Wada and Y. Maeda, Appl. Phys. Lett. 52 (1988) 60. WI T. Hiramoto, Y. Mocbizuki, T. Saito and T. Ikoma, Jpn. J. Appl. Phys. 24 (1985) L921. IV. ION IMPLANTATION

356 [Ill

T. Wada, A. Takeda / Electron beam doping

T. Itoh and M. Takeuchi, Jpn. J. Appl. Phys. 16 (1977) 227. [12] T. Tabata, R. Itoh and S. Okabe, Nucl. Instr. and Meth. 103 (1972) 85. [13] T. Wada, K. Yasuda, S. Ikuta, M. Takeda and H. Masuda, J. Appl. Phys. 48 (1977) 2145. [14] J.C. Bourgoin and J.W. Corbett, Radiat. Eff. 36 (1978) 157.

of Si into

GaAs

[15] E. Baldinger, W. Czaja and A.Z. Farooqi, Helv. Phys. Acta 33 (1960) 551. [16] D.V. Lang and L.C. Kimerling, Phys. Rev. Lett. 33 (1974) 489. [17] T. Wada, M. Takeda and K. Yasuda, J. Electron. Mater. 14 (1985) 171. [18] T. Wada and M. Takeda, Nucl. Instr. and Meth. B21 (1987) 574.