InP wires

Microelectronic Engineering 11 (1990) Elsevier Science Publishers B.V.

11

1 l-14

Magnetoresistance

measurements InGaAs/InP

A. Menschig. 4. Physikalisches D 7000

wires

A. Forchel.

B. Roos.

, Universitat

Institut Stuttgart

R. Germann

Stuttgart

. Federal

80

ln microstructured

Pfaffenwaldring

Republic

57

of Germany

W. Heuring Physikalisches

Institut.

Universit;it

Wiirzburg.

D 8700

Wtirzburg

D. Grutzmacher Institut

ANract.

Microstructured

ted

modulation

from

40mK.

The

about

4

and

The

compared

higher

Introd~ctlon. pers and

2D

focused to

etching, to

metal

of

of

wide

wires. level

Most

narrow In

this

paper

In,,sGa.,rAs/InP wire

definition,

low

pressure

quantum

level

wires strong we

The

the

50pm

with

decreasing only

fabrica-

fields

down

wire

very

a distinct

magnetic

were

magnetoresistance

indicating

on

to

width

only

dry

etch

small

resistance

and

maximum

Shubnikov-de-Haas

etch

is

are carrier

doped density

an electron

reduce

to

a lot

pain

transition

of

work

3D

from

has

nanostructures

been

C21 and

C41. by

the

effective

the

observation

be

of

deep

are

or

the

wire

shallow damage

width. of

ascribed

depleted

dry leads

Depleted

1D

effects

in

to

pinning

of

less

thicknesses

should

important

properties be

of

h

*

especially

than etched

20nm

steep

and

C61. in

be observed. and

widths the &

is

and

studies SOurn.

heterostructures localized

two-dimensional

= 100000

0167-9317/90/$3.500 1990, Elsevier Science Publishers B.V.

80nm

double

2DEG

at 2K in the

magnetotransport

between

In .ssGa.aTAs/InP

mobility

optical

layer

fabrication

which

significantly

the

in InGaAs

should

in

the

In particular,

layers

theoretical properties

sidewalls.

known

geometrical used,

now wires

damage.

depleted

typical

the

to

on

fabricated

allowed

etched

potential

on

Up

and

transport

inversion-layer

wires,

the

the

of

GaAs/GaAlAs

dry

pinning

experimental

concentrated

silicon

which

1D effects

with

of

dependence

CSI have

indicate

modulation

crnA2 with

number

investigations

report

wires MOVPE

well.

= 1.3 * 10”

and

finite

B10.3T.

lower

Aachen

80nm

a

width, for

at

etched

layers

1D confinement

channels

between

behaviour.

commonly

particular,

the

wire

interest

Ill,

on

at mid-gap

In,ssGa,,7As/InP

increases

quantum

150nm

in

Therefore

wires

the

wires

depleted

about

Fermi

In

of the

a large

131 or dry

In In.ssGa.47As GaAs.

show

(UCF’s)

recently

significantly

formation

Fermi

wires

dimensionality

GaAs/AlGaAs

widths

0.4pm the

of

depend

the

layer

years

the

defined

properties

widths

All

5Oirrrt

one-dimensional

small

electrostatically The

past

More

two-dimensional on

D 5100

with

magnetoresistance

fluctuations

on

systems.

published

at

Aachen.

fields. the

In

have

value

a negative

resistance

at

wires

heterostructures.

to the

show

reproducible

oscillations

RWTH

= OT. T = 40mK)

(B

wires

Halbleitertechnik.

In ,S3Ga,47As doped

resistivity

times

damage.

fur

cm’/Vs.

in

the

grown

by

a 12nm

electron

of

For

gas

InGaAs is N2D

12

A. Menschig

Sample

Z4eparation

fabricated

by

lithography used.

aM-CMS on,

resists the

has

high

some

various

between ration

80nm

Exposure resist

gas

mixture

depths On

and

at

were

advantage

that

each

microscope.

perature

measurements

the

into

magnetotransport

the

energies etch

etch

(65nm) of

gold-wire out the

experiments

C81. Compared

for

x-ray

contrast

a series 20pm

of

long

(y

we

spot

SOpm wires

>

used

sizes

of

a SOkV

accele-

1Onm

to

were with

different

the

with

with

exactly

the were field

a lock-in

the

were of to

same measured

a 80nm

with

at

perpendicular

Figure

etch

the

This

wire.

refrigerator was

ArIO spacer

has

technological

the

technique

an

well.

widths.

contact

oriented

and

quantum

different

picture

dilution

layer

InGaAs/InP

wires used

doping

25nm.

used.

. Two

the

a

wires widths

milling

11 wires

8),

long

by ion

and

through

to

with

80 $/cm’(aM-CMS)

in which

were

applicati-

SOOeV

in a He3/He4 magnetic

40nm high

exposure

250eV

an SEM

bonds

an expe-

CXM-CMS

heterostructure

of

1 shows

of

with

of

resist

of

fabricated

dimensions

with

and

pads, beam

C71.

of

beam

current

(S2nm),

a set

was

Figure

carried

40mK

electron beam

tone

contact electron

available to

a very

solutions

a series

by

developed

consists

and

(RAY-PN)

prepared

geometrical

were and

the

etched

wire

pattern

SOOpA

down

example

in aqueous

SOpm)

For

to

a deep

we

The

4K

up

a medium

meters.

surements

to

was

electron

ween

resist

(120nm

40 PC/cm*

and

sample

defined

negative

originally

for

defined

commercially

patterns

RAY-PN,

advantages:

acceleration

used:

removed, each

of

pattern

resist

of

were

sensitive,

and the

definition

beam

420nm.

20pA

doses

The

were

widths

voltage,

)

AuGe/Ni/Cr/Au

wires

an electron

no degradation

lithographically

with

the

interesting and

As

( RAY-PN

allow

electron

sensitivity

The

etching. resist

measurements

alloyed

In .s3Ga,,7As

lithography,

dry

electron

Both

Between

and measurement.

optical

and

rimental

et al. / Magnetoresistance

mainly

For

sample.

a

the

parascanning low

tem-

The

mea-

temperatures to

the

bet-

2DEG.

used.

1:

A SEM picture of a 80nm InGaAs/ InP wire fabricated

with a RAYPN

etch mask and dry etch techmque.

For

13

A. Menschig et al. I Magnetoresistance measurements Experimental results. Figure 2 depicts GaAs

wires

at

widths below ring

40mK

for

zero

the resistivity

magnetic

iurn. This is due to the influence

at the etched

temperature

sidewalls

the resistivity

4 higher than the constant

InGaAdlnP

charge

or

resistivity

depleted

(medium

value defined

Ar/o,

.

a.

T-M

active

surements are nearly Maile et al. 181.

wire

width

identical

therefore

By performing

magnetotransport of

the

electron

values

Typical

fields

2) At fields defined

should

magnetic

appear for

wire width. good

negative

region

field

from

depleted

layer

here from

resistance

mea-

in

experiments

40mK

optical

we

have investigated

curves

of

3 . Four features

magnetoresistance

a distinct

scales

decreasing

resistance amplitudes

with

a 80 nm

by

the

and a

should be menti-

usually

with cyclotron

fluctuations (universal

resistance the

magnetic

The half height position

agreement

calculated

resistance.

attributed

to

is observed.

but very irregular

3) In the same field

at

resistance

in figure

B 1 0.3 T reproduceable

periodicity

sponding

the typical

effects

20nm and the

extracted

determined

measurements gas.

190nm wire taken at 40mK are plotted oned. low

is about

layer widths

with

dimensionality

very

leads to a cut-off

width for finite

1OJ wire width I_, / n:

30nm. The values for the depleted

1) At

polation

8 -110,4

I~~~~,

weak localisation

- width dependence

wires at 40mK.

63nm

geometric01

electrical

width dependence

4.2K and 300K. A linear extra-

.

0.

52nm

ld

The

of

wires at 40mK.

of InGaAs

. .

this

2:

Conductivity

. .

At

a factor

Inset:

. .

200

wire

wire widths.

of InGaAs

.

I

L ; u

etch depth

regions.

Resistivity InGaAvlnP j60

for

by e.g. scatte-

is only about

by the larger

¶d

l

sidewall

Figure

of the In-

increases

sidewall

etch)

#80

T=4OmK

dependence

resistivity

of the wire

carrier

of a 80nm wire

- width

The

field.

wire

field,

if

which

have no

fluctuations).

maximum is obvious. The correA rise in magnetoresistance

width.

the cyclotron

and the field

diameters

appear

conductance

position

and cyclotron

diameter

reaches

of the maximum

radii positions,

the

are in

respectively,

the 2D carrier density and the measured wire widths.

4) At

higher magnetic fields typical Shubnikov-de-Haas oscillations are observed. of the quantum numbers of the The inset of figure 3 shows a usual fan diagram magnetoresistance minima plotted versus the reciprocal magnetic field. No deviation from the linear l/B dependence down to 0.8 T is found for wires wider than 310nm. But pronounced tes

the formation

deviations

are obvious

of 1D subbands

C91.

for

the smaller

wires.

The

deviation

indica-

A. Menschig et al. I Magnetoresistance measurements

14

lnGa,&/lnP

#8()

InGaAs/lnP

l

#80

. . ..****.*.3lonm

c 40_

01

6

5

I

I

1

2.5

0

I

7.5 field

rnogn~k~

10.0

[ T I

Figure 3: Two typical curves of longitudinal resistance (80nm and 190nm wire width) at 40mK are shown. The inset depicts procal magnetic

field

Ihe dependence

for different

of Landau level number over Ihe reci-

wire widths (310nm.

190nm.

150nm.

IlOnm and

80nm).

COZZC~US~OXI. We have a finite res down ductance

to 80nm. fluctuations

with large

nikov-de-Haas-oscillations surface

scattering

due

in our medium

and G. Landwehr

RAY-PN.

for

the experimental

K. Thonke state.

and K. Pressel

for

A. Benoit. C.P. Umbach. R.B. Laibowitz.

stimulating

making

assistance the help

universal

in the periodicity

ID subbands

corporation

We acknowledge

. We thank K. Grijtsch

Steinmetz

of

InGaAs/InP

we found and

of

an

their

discussions

with

available

at the

with

for providing

his analyzing

He3/He4

-

M.L. Roukes. A. Scherer. S.J. Allen,

the measurements

experimenM. Pilkuhn

cryostate

R.A. Webb; Phys. Rev. Lett. 58

H.G. Craighead.

, 2343 (1987)

T. Demel. D. Heitmann. P. Grambow. K. Ploog, Appl.

Phys. Lell. 53

B.E. Maile.

Appl. Phys. Lett. 54

R. Dammel. K.-F. D&sel. J. Lingnau. J. Theis: Microelectr. B.E. Maile.

A. Forchel.

R. Germann. A. Menschig.

Eng. 7

J.P. Harbison,

H.P. Meier; J. Vat.

G. Roos. H. van Houten: Phys. Rev. B37

2176 (1988) 1552 (1989)

. 575 (1988)

2308 (1988) K.-F. Berggren.

951 (1982)

, 1769 (1986)

R.M. Ruthen. E.D. Beebe,

R. Germann. D. Griitzmacher;

10118 (1988)

N. and

at our magnet-cryo-

, 3011 (1987)

A. Forchel.

of

program,

dilution

T.J. Thornton. D.J. Newson. M. Pepper; Phys. Rev. Lett. 57

Phys. Rev. Lett. 59

the Shub-

influence

W.J. Skocpol. L.D. Jackel. E.L. Hu. R.E Howard, L.A. Fetter; Phys. Rev. Lett. 49 K.-F. Berggren.

wicon-

transport.

We thank the Hoechst

system

changes

formation field

deep etched

measurements

amplitudes, to

on low magnetic

A&owledgement. tal resist

resistance

In the magnetotransport

Sci. Technol.

B6