Investigating galvanomagnetic effects in developing higher magnetoresistance devices for low voltage high current switche

Grannemann, W. W.

Kim, T. W.

Yu, H. Y.

English

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THE UNIVERSITY OF NEW MEXICO
Bureau of
_ Engmeenng
Lt J Research
Albuquerque
MAGNETORESISTANCE DEVICES
By
T. W. Kim
H. Y. Yu
W. W. Grannemann
Progress Report PR-92(69)NASA-028
,July 1969
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Prepared for NASA NeG 3P.004-002
UniuR,reity of New Mexico No. 280
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MAGNETORESISTANCE DEVICES
by
T. W. Kim
H. Y. Yu
W. W. Grannemann
Progress Report PR-92(69)NASA-028
July 1969
Prepared for NASA NsG 32-004-002
University of New Mexico No. ,_290
rx
MAGNETORESISTANCE DEVICES
Introduction
This work is a continuation of the project on galvano-
magnetic effects. Its aim is to find higher magnetoresis-
tance devices for a low-voltage high-current switch.
Previous studies have been made of the effect of the
geometry of indium antimonide (InSb) and bismuth (Bi) magneto-
resistance devices [References 1 and 2]. According to pre-
vious results, lowering of the Hall voltage can create higher
magnetoresistance. Use of the Corbino disk has obtained the
best results. Its magnetoresistance coefficient may reach
51 at room temperature [Reference 11. We shall extend the
previous analysis and try to find even better results.
One of our proposed studies is the use of self-b,as.ed
electrical-field-enhanced magnetoresistance devices. We
shall adopt the best geometrical shape and use the electric
field effect to increase the magnetoresistance of the de-
vices. Next, we plan the use of an InSb p-n junction to get
higher magnetoresistance. Finally, we propose the use of
p-n-p or p- i-n magnetic field-sensitive devices; these are
described in the last section.
Magnetoresistance
The magnetoresistance phenomenon has close relationship
with the Hall effect. The current changes its direction
I - as.
1
F	 1
tit	 n
when a magnetic field is applied perpendicular tQ the cur-
rent direction. That is, the current flows over a longer
path than before. The material has more effective resistiv-
ity with a crossed magnetic field. There is a difference
in the magnetoresistance phenomenon and the Hall effect that
is causad by geometrical shape. A high Hall voltage device
may accompany a low magnetoresistance coefficient. Both the
Hall voltage and magnetoresistance coefficient are dependent
upon the geometry of the device.
Lippmann and Kuhrt [Reference 31 derived the low-field
	
magnetoresistance of a rectangular isotropic spec ; :nen by	 P
conformal mapping in terms of Hall angle 6, the resistivity
in a magnetic field p B , the corresponding resistivity in
zero field p o , and a function of geometry g(k/w), evaluated
numerically and graphically:
RB = pB [1 +g ( .L)tan 2 6]	 (1)
R 	 po	 w
Since (p B/Po 	 ( 
uo
/V B ) , and since tan 26 = ( uBE) 2 , Equation
1 may be expressed as
RR 
= uu + [g (W)• 	 DU • II I B 2	 (2)
o	 B
where Ap/uB is a "physical magnetoresistance" in small mag-
netic fields, which may be considered negligible in compari-
son with the geometrical magnetoresistance which is quadratic
in B. Lippmann and Kuhrt have shown that the magnetoresist-
ance coefficient in high magnetic fields  and for-large ( k/w) ,
rmay be expressed as
^
	
RR	 + (T) IuoB - u
11 0 "
^ • n ln2 ]	 (?)
	0 	 o	 B
The magnetoresistance coefficient (BR/Ro) of monophase,
riendritic InSb films is a quadratic function of the magnetic
field B, for uB«1, and a linear function of B in high
magnetic fields [Reference 41.
Simmo.is [Reference 61 confirmed that the enhancement of
the magnetoresistance effect in rectangular elements is due
to the Hall effect rather than to is absence. He also showed
that the bulk property has a B 2 relationship while the geo-
metrical effect is linear in B and inversely proportional to
the length-to-width ratio.
Experimental Procedures Being Investigated
1. Geometrical Shape of Magnetoreaistance Devices
The geometrical shape of magnetoresistance materials has
been investigated by several authors [References 1, 2, 4, and
51. They confirm that the geometrical shape is very import-
ant to the magnetoresistance coefficient of the materials.
Corbino disks and modified devices with shorting electrodes
of the Hall voltage are among the best shapes to produce the
optimum of the magnetoresistance coefficient. This is due to
the shorting of the Hall voltage.
In addition to the geometrical shapes, the most important
factors in obtaining the best magnetoresistance are the
3
t
r.'	 F
+a
^tttiM1i
4
Y
^y
s
u	
^pa
:t
=Y,
choice of material and the reducing of the contact resist-
ance of the electrodes. InSb is considered to be t. N e best
material for magnetoresistance devices at room temperature
while bismuth is the best material at low temperature, be-
cause of their high carrier mobility. Contact resistance
of the electrodes can cause an increase in the zero field
resistance and this can reduce the magnetoresistance coef-
ficient. For InSb, indium alloyed into the contact surface
of the InSb bulk material can reduce the contact resistance
[Reference 11 .
Several geometrical shapes of the bulk magnetoresistance
devices, which will be considered later, are shown in
Figure 1.
2, Self-Biased Electric-Field-Enhanced MOS Magnetoresis-
tance Device
A self-biased electric-field-enhanced MOS magnetoresist-
ance device is a two-terminal passive device. We will use
the Corbino disk geometry shape with self-biased gate volt-
age on a MOS device. The structure of this device is shown
in Figure 2. This device is the combination of a magneto-
resistance bulk device and the MOS device. Without applying
the magnetic field, the voltage drop on the terminals of this
device is small. The lower gate voltage does not have too
much effect on the resistance of the device. When a magnetic
field is applied to the device, due to the structure of the
Corbino disk, the resistance of the device increases, and as
4	 -
I'
1
tage
nt
(f)
(a)
Corbino Disk
(c)
Electrode Shorting
(e)
(b)
C^
Hall
Voltage
Shunt
Figure 1. Six Different Geometrical Shapes of the
Bulk Magnetoresistance Devices
, R
5 Ak
Dielectric Layer
_Drain
dn
 Reverse Biased
Source
Gate
Drain
z:
b, n type
ulator substrate or
ype InSb
Figure 2. Self-Biased Electric-Field-Enhanced MOS
Magnetoresistance Device
6
^.LI
em.	
t
 t°
i
" t4x
a result the voltage on the terminals also increases. There-
fore, the higher voltage on the gate cuts more current.
Such a type of self-biased magnetoresistance device has a
higher magnetoresistance coefficient. This is the main
idea of the device. We will work on the structure of this
device in order to attain the best performance on the
magnetoresistance coefficient (AR/R0). A p-n InSb wafer or
an InSb fily on the insulator substrate will be used for the
MOS structure.
3. =n Junction Magnetoresistance Devices
Different arrangements of a high carrier mobility p-n
junction have different resistances under different direc-
tions of the magnetic field applied. Several different
models of the p-n junction magnetoresistance devices ara
briefly described below.
a Reverse-biased p-n junction
A reverse-biased p-n junction device is shown in Figure
3. It is polished and etched except for one side of the
p-n junction, which is lapped. When the magnetic field is
applied in a proper direction, the carriers flow to the side
of the smooth surface. However, the carriers flow to the
other side of the lapped surface for a different direction
of the magnetic field. Different recombination velocities
at different surface states have different properties. It
is expected that there is a low value of the resistance of
7
OB
e	 • 0
-0 Reverse- Biased
1 , f,	 Polished and etched surface
®	 ®
mb^ p	 n	 Reverse-Biased
Lapped Surface
B
•' . P .^
	
•moo Reverse-Biased
Figure 3. Reverse-Biased InSb p--n Junction
the device when the carriers flow to the lapped surface at
the junction.
b. Forward-biased p-n junction magnetoresistance device
In a forward-biased p-n junction magnetoresistance de-
vice, the electrodes are connected on one aide of the p-n
junction as shown in Figure 4, and the device is forward-
biased. When the magnetic field is applied to keep the car-
riers bending toward the junction, the device has lower
resistivity., If the magnetic field is in ;:he opposite direc-
tion, the carriers must find the longer way to complete the
passage. This device, therefore, has higher resistance. It
is hoped that its magnetoresistance coefficient will be highei;
than the basic magnetoresistance devices.
c. Reverse-biased p-n junction magnetoresistanc-a device
A reverse-biased InSb p-n junction with electrodes on
one side of the junction is shown in Figure 5. With the
proper direction of the magnetic field, the carriers flow
toward the p-n junction. In the opposite direction, the car-
riers flow outward from the electrodes to follow the complete
path through the outside-shorted bar. This device is non-
linear under the magnetic field.
4. p-n-p or p-i-n Magnetoresistance Devices
It is well known that the change of the width of the
center region of p-n-p or p-i-n structures can change the
collector current for onstant terminal voltage. That is,
9
1
Forward-Biased
e
r0B
Forward-Biased
Forward-Biased
,, r
u
e„
ce, ` .C.ae	 uir* `.	 k	 _	 #
o-
^p
bi
r
OB
a® be
Figure 4. Forward -Biased p-n Junction Magnetoresistance
Device
	a	
Reverse-Biased
749
	
y	 V
d
OB Reverse-Biased
FZ
	't
1 9 749
	
' 	 .+^p
N)tF
(4
Figure 5. Reverse-Biased p-n Junction Magnetoresistance
Devices with Long Bar Structure
..	
..	
^,..
	
a	
..	 _
d
the wider center region has less collector current. If we
construct the p-n-p or p-i-n devices to have a wider center
region (width/diffusion length V 5) , we have the following
interesting results:
Without applying the magnetic field, the current flowing
through the device is small compared with that of the regular
structure. But when the magnetic field is applied to this
device, due to the Corbino structure, the device has a longer
path for the carriers at the center region. In other words,
the effective width is increased. If the effective width
increases to twice its previous width the W/L ratio can reach
10. By the p-n-p transport factor formula [Reference 61, the
collector current can be reduced from its original value by
a factor of 1501 Such an arrangement has high sensitivity
in the magnetic field and a high magnetoresistance coeffic-
ient. The main disadvantage of this device, however, is an
increase in resistivity.
v	 ..mow .:
	
`c4	 1
REFERENCES
1. Bechtel, R., Grannesmann, W. W., and Har, ter, B. J.,
"D.C. to A.C. Conversion using Magneto-Resistance,"
Solid State Electronics, Vol. 7, 1964, p. 357.
2. Bechtel, R., and Grannemann, W. W., Report EE-131,
University of New Mexico, December 1965.
3. Lippmann and Kuhrt, "Der Geometrieeinf luss auf den
transversalen magnetischen Widerstandseffekt bei
rechteckformigen Halbleiterplatten," Zeitschrift
fur Naturforschung, Vol. 13a, 1958, p.-671.
4. Wieder, H. H., "Galvanomagnetic Properties of Re-
crystallized Dendritic InSb Films," Solid State
Electronics, Vol. 9, 1966, p. 373.
5. Simmons, C. A., "Influence of the Hall Effect upon
the Transverse Magnetoresistance in Indium Antimonide,"
J. Applied Phys., Vol. 32, 1961, p. 1970.
6. Sze, S. M., Physics of Semiconductor Devices, Wiley-
Interscience, 1969.


Magnetoresistance devices  Progress report

Magnetoresistance devices and flash evaporation equipment design for indium antimonide researc

https://ntrs.nasa.gov/search.jsp?R=19700020561 2020-03-12T02:33:29+00:00Z
MAGNETORESISTANCE DEVICES 
T. W. Kim 
H. Y. YU 
W. W. Grannemann 
Progress Report PR-94 (70) NASA-028 
March 19'40 
Prepared for the National Aeronautics 
and Space Administration under Contract 
No. NGR32-004-002 
TABLE OF CONTENTS 
Introduction 
Properties of Indium Antimonide 
Geometry Shapes of Magnetoresistance Devices 
A Special Magnetoresistance Device 
Flash Evaporation 
Hall Effect on InSb Thin Films 
References 
Page 
1 
1 
3 
11 
18 
20 
2 4  
LIST OF FIGURES 
Page 
Figure 1. 
Figure 2. 
Figure 3. 
Figure 4. 
Figure 5. 
Figure 6. 
Figure 7. 
Figure 8. 
Figure 9. 
Figure 10. 
Figure 11. 
Figure 12. 
Figure 13. 
Magnetoresistance of sample #9 with 
different bias currents in the magnetic 
field. 
Voltage of sample # 9  in the magnetic 
field with constant bias currents. 
Magnetoresistance of the sample versus 
sample current. 
V-I characteristics of the sample with 
or without the magnetic field. 
A special biased diode magnetoresistance 
device. 
Magnetoresistance Versus magnetic field 
of the special magnetoresistance device 
(sample #lo) with open and short Hall 
terminal conditions. 
Magnetoresistance versus magnetic field 
in sample #10 with a silicon diode 
connected to the Hall terminals. 
MR o en Magnetoresistance ratio (MR ,EOrt of 
sample #lo. 
A high-magnetoresistance ratio and 
asymmetric device. 
Flash evaporation vacuum system. 
Substrate heater, powder-sending system 
of the flash evaporation system. 
Hall voltage of thin InSb film with dif- 
ferent bias currents. 
The InSb thin film sample with measuring 
circuit. 
G4AGNETORESPSTmCE DEVICES 
I n t r o d u c t i o n  
S ince  l a s t  J u l y ,  we have investigated t h e  geometry 
shapes on magnetores i s tance  i n c l u d i n g  t h e  modified Corbino 
d i s k .  A s p e c i a l  non l inea r  and asymmetric magnetores i s tance  
dev ice ,  u s ing  a diode t o  d r i v e  t h e  Ha l l  t e r m i n a l s ,  has  been 
made. I t  shows some i n t e r e s t i n g  r e s u l t s  which w i l l  be d i s -  
cussed l a t e r .  We designed and i n s t a l l e d  t h e  f l a s h  evspsra -  
t i o n  equipment f o r  Indium Antimonide t h i n  o r  t h i c k  f i l m  re- 
sea rch .  We a l s o  measured t h e  mob i l i t y  of Indium Antimonxde 
t h i n  f i l m  by t h e  f l a s h  evapora t ion  method. 
The s e l f - b i a s e d  e l e c t r i c  f i e l d  enhanced magne to re s i s t -  
ance dev ices  which a r e  proposed i n  t h e  l a s t  r e p o r t  (1) will 
be i n v e s t i g a t e d  a f t e r  w e  o b t a i n  t h i c k  Indium Antimonide film 
P r o p e r t i e s  of Indium Antimonide 
Indium Antimoni.de i s  one of  t h e  most impor t an t  materials 
f o r  t h e  magnetores i s tance  dev ices .  I t  i s  necessary  to de- 
s c r i b e  and d i s c u s s  i t s  p r o p e r t i e s .  
Because of  i t s  high m o b i l i t y  p r o p e r t i e s ,  Indium Anti-  
monide i s  one of t h e  I I I - V  compound semiconductors which have 
been almost  f u l l y  explored  by s c i e n t i s t s .  The e l e c t r o n  mobil- 
i t y  i n  Indium Antimonide i s  very  l a r g e .  This  i s  due t o  i t s  
smal l  e f f e c t i v e  mass. The p h y s i c a l  p r o p e r t i e s  of Indium 
Antimoni.de a r e  l i s t e d  i n  Table 1, 
TABLE 1, PHYSICAL PROPERTIES OF InSb 
Physical Properties Descriptions 
Crystal Structure Zfncblende 
Lattice Constant at 300°K 6.4788i 
Melting Point 525'C 
Effective Mass of Electrons (0.016t0.007)me ( 2 )  0. 036me ( 3 )  
Energy Gap at 300°K 0.167 eV 
Energy Band Structure Direct energy band. The mini- 
mum in the conduction band 
occurs at k=O and the constant 
energy surfaces are spherical 
near the minimum. The maximum 
in the valence band is also at 
k=O, but this band is degener- 
ate so that two types of hole 
should occur as for silicon 
and germanium ( 2 )  
Mobility of Electrons We = e~/m, 
Minority Carrier Lifetime second near room ternpera- 
ture for purest crystal; 5x10-9 
second for the doping dens~ty 
of lo1' cm-3e Near room 
temperature, both n type and p 
type material, the lifetime 
increases rapidly as the 
temperature decreases. (2). 
It is known that Cd and Zn act as acceptor impurities 
and are frequently used to provide p type material, while Te 
acts as a donor impurity and is used to provide n type mate- 
rial (2). Usually the impurity energy level above or below 
the valence band and conduction band is about 0.01 eV. At 
2 
room temperature, the mobility of 77,000 cm /V-sec can be 
obtained. 
Geometrv Sha~es of Maanetoresistance Devices 
The geometry shapes of magnetoresistance devices have 
been investigated by several authors (4) ( 5 )  (6) 7 They 
show that the Corbino disk shape has the highest magnetore- 
sistance. The reason is due to the short circuiting of the 
circumferential Hall field induced in the disk by the orthog- 
onal electric and magnetic fields. 
We have nine samples with different geometry shapes of 
magnetoresistance devices. The length/width ratio is about 
0,625 on sample #l, l/w = 1.0'7 on sample # 2 ,  and 1/w = 5.5 on 
sample # 3 .  Our results show that sample # 2  has a higher 
magnetoresistance than sample #3. This coincides with the 
results from the mentioned authors. However, the lower 
magnetoresistance on sample #l is due to the high contact 
resistance compared with the bulk resistance, Samples #4, # 5 ,  
and #6 are specially designed geometry shapes. All electrodes 
are on one side of the sample with small spacing. Under very 
weak magnetic field, the sample shows asymmetric properties 
of magnetoresistance. However, it tends to saturate as the 
magnetic f i e l d  i n c r e a s e s .  Sample # 7  i s  l i k e  a c a p a c i t o r  w i t h  
two e l e c t r o d e s  mounted on t h e  s u r f a c e s  of  t h e  Indium Antn- 
monide wafers .  The low magnetores is tance of t h i s  sample i s  
a l s o  due t o  t h e  c o n t a c t  r e s i s t a n c e .  Sample # 8  i s  a t r i a n g l e -  
l i k e  shape.  We use  t h e  copper -p la t ing  method t o  make t h e  
c o n t a c t  e l e c t r o d e s  on t h e  above samples.  Then we use  t h e  
s o l d e r  t o  connect  t h e  l eads  t o  t h e  e l e c t r o d e s .  Sample # 9  i s  
c a l l e d  t h e  modified Corbino d i s k .  The o u t e r  e l e c t r o d e  i s  
r ec t angu la r  i n s t e a d  of c i r c u l a r .  Our r e s u l t  shows t h a t  t h i s  
modified Corbino d i s k  i s  comparable w i th  t h e  r e g u l a r  Corbino 
d i sk  i n  magnetores i s tance .  
Experimental  d a t a  on our  n ine  samples a r e  l i s t e d  on 
Table 11. Figure  1 shows t h e  magnetores i s tance  ve r sus  mag- 
n e t i c  f i e l d  w i t h  d i f f e r e n t  b i a s  c u r r e n t s  a t  room temperature  
on a modified Corbino d i s k  (sample # 9 ) .  The h ighe r  b i a s  cur-  
r e n t  may cause  t h e  temperature  r i s e  and reduce t h e  magneto- 
r e s i s t a n c e  a s  expected.  However, when t h e  b i a s  c u r r e n t  i s  
smal l  enough, t h e  c o n t a c t  r e s i s t a n c e  o r  c o n t a c t  p o t e n t i a l  on 
t h e  c o n t a c t  a r e a  of t h e  e l e c t r o d e s  causes  t h e  drop of t h e  
magnetores is tance.  F igure  2 shows t h e  e l e c t r o d e  vo l t age  
ve r sus  magnetic f i e l d  w i th  d i f f e r e n t  b i a s  c u r r e n t s .  From 
t h i s  f i g u r e ,  Ib = 1 0 0  ma has t h e  s t e e p e s t  s l o p e ;  t h e r e f o r e ,  
it shows t h e  h i g h e s t  magnetores i s tance .  The magnetores is tance 
ve r sus  b i a s  c u r r e n t  i s  shown i n  F igure  3. F i n a l l y  t h e  I - V  
curve of sample # 9  w i t h  o r  wi thout  magnetic f i e l d  i s  shown 
i n  F igure  4 ,  On t h e  modified Corbino d i s k ,  t h e  magnetore- 
s i s t a n c e  va lue  (AR/Ro) i s  about 35.7 a t  15 k i l o g a u s s .  T h l s  
TABLE i l  
TABLE I I (Cont.) 
Figure 1. Magnetoresistance of sample # 9  with different 
bias currents in the magnetic field. 
0 I 2 3 4 5  6 7 8 9 1 0 1 1 I 2 1 3  
5 (kllogauss) 
Figure 2. Voltage of sample # 9  in the magnetic field 
with constant bias currents. 
36 
3 4 
3 2  2 
3 0  
z 
a 
b- 
52 
2 8  
cc 
i 
W $ 26 
4 
H 
2  4 
2 2 
2  0  
0  2 0  4 0  6 0  8 0  100 120 140 160 180 2 0 0  2 2 0  
S A M P L E  C U R R E N T  (ma)  
Figure 3. Magnetoresistance of the sample versus 
sample current. 
Sample No. 9 
M o d l f l a d  Corb lno  Disk 
Figure 4. V-I characteristics of the sample with or 
without the magnetic field. 
i s  comparable wi th  t h e  r e p o r t  by R e  Bechte l  and W .  W a  
Grannemann ( 5 ) .  W e  use t h e  Indium a s  t h e  s o l d e r  f o r  t h i s  
modified Corbino d i s k  i n  o r d e r  t o  o b t a i n  b e t t e r  c o n t a c t .  
A S p e c i a l  Magnetores is tance Device 
A s p e c i a l  magnetores i s tance  dev ice  was i n v e s t i g a t e d  l a s t  
Winter .  We know t h a t  t h e  opening o r  s h o r t i n g  o f  t h e  H a l l  
v o l t a g e  t e rmina l s  may change t h e  magnetores i s tance  of t h e  
dev ice ,  I f  t h e  Ha l l  v o l t a g e  i s  i n  t h e  range of  a few v o l t s ,  
then  a d iode  can swi tch  t h e  Ha l l  t e r m i n a l s  from "open" t o  
" s h o r t "  o r  v i c e  v e r s a  under d i f f e r e n t  d i r e c t i o n s  of t h e  b i a s  
c u r r e n t  o r  magnetic f i e l d .  I n  o t h e r  words, h ighe r  Ha l l  
v o l t a g e  can d r i v e  t h e  d iode  under bo th  c o n d i t i o n s .  I n  t h i s  
c a s e ,  we have t h e  asymmetric p rope r ty .  The change of t h e  
magnetores is tance depends upon t h e  shape of t h e  dev ices .  
Seve ra l  d i f f e r e n t  shapes  of t h e  dev ice  have been made, e . g . ,  
r e c t a n g u l a r  ( l eng th /wid th  = 4 )  and square  ( l eng th lwid th  = 1). 
A s  an example, a  square  sample 8.5 mrn by 8 .5  mm by 1 mm was 
cons t ruc t ed ,  u s ing  p o l y c r y s t a l  Indium Antimoni.de wi th  t h e  
2 
mobi l i t y  50,000 cm /V-sec a t  80°K. The va lue  of t h e  magneto- 
r e s i s t a n c e  r a t i o  i s  1 . 6 2  (open) : 1 ( s h o r t )  a t  1 0 0  ma b i a s  
c u r r e n t  wi th  3 k i l o g a u s s  magnetic f i e l d  under l i q u i d  n i t r o g e n  
temperature .  The va lue  of  t h e  magnetores i s tance  r a t i o  can be 
inc reased  by op t imiz ing  dimensions and t h e  e1ectrod.e shape ,  
A room temperature  dev ice  can be made from a very  t h i n  InSb 
s l i c e  o r  InSb f i l m  by us ing  t h e  f l a s h  evapora t ion  method wi th  
proper  annea l ing .  A t  a  s p e c i f i c  range of t h e  magnetic f i e l d  
( 3  kilogauss in our square sample), we obtained the peak value 
of the magnetoresistance ratio. This value decreases as the 
magnetic field increases or decreases from this optimum point. 
As we connected a silicon diode at the Hall terminals of this 
sample, we found that under reverse bias of the diode the 
curve of the magnetoresistance versus the magnetic field is 
the same as the curve when the Hall terminals are open. How- 
ever, the condition on forward bias of the silicon diode is 
different. The curve stays close to the open curve until the 
applied field increases to a certain value, it then shifts 
from the open curve region to the closed curve region. This 
happened at 4.6 kilogauss with 100 ma bias current and 3.6 
volt bias voltage on our square sample. The shift region de- 
pends upon the size of the sample and the characteristics of 
the diode. 
Figure 5 shows the structure of this sample (#lo) with 
measuring circuit. The magnetoresistance of the sample with 
open or short Hall terminals versus magnetic field is shown 
in Figure 6. Figure 7 shows the characteristics of the 
magnetoresistance in the sample with a silicon diode connected 
versus the magnetic field on different bias currents. Figure 
8 shows the magnetoresistance ratio of the sample with Mall 
terminals open and short and for different directions of the 
sample current under the magnetic field. 
Theoretically, the magnetoresistance ratio on this 
special magnetoresistance device may be increased up to 10 by 
the arrangement as shown in Figure 9, 
HALL 
Figure 5. A special biased diode magnetoresistance 
device. 
Figure 6. Magnetoresistance versus magnetic field of 
the special magnetoresistance device (sample #lo) 
with open and short Hall terminal conditions. 
Sample No. 10 with forward  
F i g u r e  7 .  P lagne to res i s t ance  v e r s u s  magne t i c  f i e l d  i n  
sample #10 w i t h  a  s i l i c o n  d i o d e  connected  t o  
t h e  H a l l  t e r m i n a l s .  
MR open 
-
MR short 
Sornple No. I0 w i t h  d iode  .F=. 
------------- 
se---8 
MR open 
Figure 8. Magnetoresistance ratio (MR short ) of sample #lo. 
Figure 9. A high-magnetoresistance ratio and asymmetric 
magnetoresistance device. 
Flash  Evaporation 
Decomposition of t h e  compound semiconductors du r ing  evap- 
o r a t i o n  i s  a problem i n  t h e  p r e p a r a t i o n  of t h e  t h i n  f i l m s .  
Recent ly ,  f l a s h  evapora t ion  seems t h e  b e s t  method f o r  ob ta in-  
i n g  b e t t e r  compound semiconductor f i l m s .  The i d e a  of f l a s h  
evapora t ion  i s  very s imple .  Suppose t h e  compound semiconductor 
powder t o  be cont inuous ly  s e n t  down t o  t h e  evapora tor  dur ing  
evapora t ion ;  even i f  decomposition occu r s ,  t h e  cont inuous 
evapora t ion  of t h e  sma l l  compound semiconductor powder r e s u l t s  
i n  f a i r l y  well-mixed compound semiconductor l a y e r s  on t h e  
s u b s t r a t e .  With proper  annea l ing  of t h e  sample o r  p roper  sub- 
s t r a t e  temperature  dur ing  evapora t ion ,  good t h i n  f i l m s  may be 
ob ta ined .  Therefore ,  t h e  f l a s h  evapora t ion  i s  one of t h e  most 
impor tan t  t o o l s  f o r  compound semiconductor t h i n  f i l m  r e s e a r c h .  
S ince  l a s t  J u l y ,  we s t a r t e d  t o  des ign ,  i n s t a l l ,  and t e s t  
our  new f l a s h  evapora t ion  system, which i s  desc r ibed  i n  
F igure  1 0 .  There a r e  two r igh t - ang le  d r i v e s  connected t o  t h e  
mechanical feedthrough.  A w i r e  i s  connected a t  t h e  end of 
one of t h e  r i gh t - ang le  d r i v e s .  This  w i r e  s e r v e s  a s  a f e e d e r  
f o r  t h e  compound semiconductor powder. The v i b r a t i o n  of t h e  
mechanical feedthrough w i l l  d r i v e  t h e  meta l  w i r e  t o  have up 
and down motion through t h e  powder h o l d e r .  Then t h e  compound 
semiconductor powder w i l l  be c a r r i e d  out by up and down motion 
of t h i s  metal  w i r e .  When t h e  powder i s  dropped down from t h e  
h o l d e r ,  t h e  powder w i l l  s l i d e  down through t h e  V-shaped sender  
t o  t h e  h e a t e r  (fused. q u a r t z  b o a t ) .  Ca re fu l ly  a d j u s t i n g  t h e  
Figure 10. 
Flash evaporation 
vacuum system 
Figure 11. 
Substrate heater, 
powder-sending 
system of the flash 
evaporation system 
v i b r a t i o n  of t h e  mechanical feedthrough w i l l  r e s u l t  i n  a 
BI 
f a i r l y  smooth sending r a t e  f o r  t h e  compound semiconductor 
powder. A s h u t t e r  i s  connected t o  t h e  mechanical feed-  
through.  The mechanical feedthrough f u r n i s h e s  double a c t i o n ,  
on t h e  s h u t t e r  and on t h e  f eed ing  of t h e  powder. 
A s u b s t r a t e  h e a t e r  i s  p u t  on t h e  t o p  of  t h e  g l a s s  sub- 
s t r a t e  a s  shown i n  F igure  11. The temperature  of  t h e  sub- 
s t r a t e  h e a t e r  can be measured by t h e  i ron-cons tan tan  thermo- 
couple which i s  connected t o  t h e  h e a t e r  through t h e  i n s t r u -  
ment feedthrough.  
Tes t ing  of t h i s  f l a s h  evapora t ion  equipment when w e  
had completed t h e  des ign  and i n s t a l l m e n t  showed good r e s u l t s  
i n  t h e  compound semiconductor t h i n  f i l m  we ob ta ined .  
Ha l l  E f f e c t  on InSb Thin Films 
Using t h e  f l a s h  evapora t ion  equipment which we designed 
and made, a f a i r l y  good InSb t h i n  f i l m  has  been ob ta ined .  
0 
The m o b i l i t y  of  o u r  sample w i th  2000 A t h i c k n e s s  reaches  
1 0 0 0  cmL/v-sec. However, t h i s  t h i n  f i l m  can be used as t h e  
f i e l d  e f f e c t  t r a n s i s t o r  ( 8 )  b u t  i s  n o t  good f o r  magnetores is-  
t ance  dev ices .  J .  A . C a r r o l l  and J. F .  Spivak ( 9 )  showed t h a t  
t h e  t h i c k e r  t h e  InSb f i l m  w i t h  proper  annea l ing ,  t h e  h i g h e r  
t h e  m o b i l i t y  ob ta ined .  When t h e  t h i ckness  of  InSb f i l m  
reaches  4 microns,  t h e  m o b i l i t y  t ends  t o  s a t u r a t e .  The mo- 
b i l i t y  of our  sample a t  t h i s  t h i c k n e s s  i s  good by c a r r o l l ' s  
s t anda rd ,  
W e  would l i k e  t o  g e t  t h i c k e r  f i l m  (abou t  5 mic rons )  w i t h  
p ro pe r  annea l i ng  and s u b s t r a t e  t empera tu re  ( 3 5 0 ° C ) .  Hope fu l l y ,  
w e  may have ve ry  h igh  m o b i l i t y  on InSb f i l m  which i s  s u i t a b l e  
f o r  t h e  magne to r e s i s t ance  d e v i c e s .  I n  t h e  f u t u r e ,  we w i l l  t r y  
t h e  MOS s t r u c t u r e  e l e c t r i c  f i e l d  enhanced magne to r e s i s t ance  
d e v i c e s  which a r e  d e s c r i b e d  i n  t h e  l a s t  r e p o r t  (1). F i g u r e  
12 shows t h e  H a l l  v o l t a g e  w i t h  r e s p e c t  t o  t h e  magnet ic  f i e l d  
w i t h  d i f f e r e n t  b i a s  c u r r e n t s .  The d imensions  of  t h e  sample 
and t h e  measuring c i r c u i t  a r e  shown i n  F igu re  13 .  
Figure 12. hall voltage of thin InSb film with different 
bias currents. 
Figure 13. The InSb thin film sample with measuring circuit. 
REFERENCES 
Kim, T. W., Yu, He Y., and Grannemann, W. W e ,  "Magneto- 
resistance Devices," Report No. 290, University of New 
Mexico, July 1969. 
Smith, R. A., Semiconductors, Cambridge Press, 1961. 
Madelung, Otfried, Physics of 111-V Compounds, John Wiley 
& Sons, 1964. 
Wieder, H. H., "Anomalous Transverse Magnetoresistance of 
InSb Films," Journal of Applied Physics, Vol. 10, 80. 8, 
1969, p. 3320. 
Bechtel, R., Grannemann, We W., and Harper, B. J., "DC 
to AC Conversion Using Magneto-pesistance," Solid State 
Electronics, Vol. 7, 1964, p. 357. 
Wieder, H. H., and Collins, D. A., "InSb Film Raster 
Pattern Magnetoresistors," Solid State Electronics, Vol.11, 
1968, p. 1093. 
Lippmann and Kuhrt, "Der Geometrieeinfluss auf den trans- 
versalen maqnetischen Widerstandseffekt bei rechteckformigen 
~albleiter~iattern, " Zeitschrift fur Naturforschung, Vol. 
13a, 1958, p. 462. 
Lile, D. and Anderson, J. C., "The Application of Poly- 
crystalline Layers of InSb and PbTe to a Field Effect 
Transistor," Solid State Electronics, Vol. 12, 1969, p. 735. 
Carroll, J. A. and Spivak, J. F., "Preparation of High 
Mobility InSb Thin Films," Solid State Electronics, Vol. 9, 
1966, p. 383. 


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