Optically induced voltage and dc characteristics of the GaAs Dual-gate MESFET and the Permeable Base Transistor (PBT) with optical illumination at wavelength below 0.87 microns were obtained and compared with GaAs MESFET. It was observed that PBT can handle higher current density when illuminated

Bhasin, K. B.

Simons, R. N.

English

NASA Technical Reports Server

NASA Technical Memorandum 88823 
Optically Controlled GaAs 
Dual-gate MESFET and 
Permeable Base Transistors P 
N87-10232 I [NASA-T8-88823) OPTICALLY CCRTAOLLED G a A s  DUAL-GATE MESEEl A N D  PERMEBELE EASE 
I K A N S I S T C R S  [ K A S A )  7 p CSCL 09A 
Unclas 
63/33 44160 
R.N. Simons and K.B. Bhasin 
Lewis Research Center 
Cleveland, Ohio 
t 
&pared for the 
Conference on Lasers and ElectmOptks (CLEO) 
cosponsored by the Institute of Electrical and Electronics Engineers 
and the Optical Society of America 
San Francisco, California, June 9-13, 1986 
f 
, 
https://ntrs.nasa.gov/search.jsp?R=19870000799 2020-03-20T13:56:26+00:00Z
OPTICALLY CONTROLLED GaAs DUAL-GATE MESFET AND PERMEABLE BASE TRANSISTORS 
R.N. Simons* and K.B. Bhasin 
Nat iona l  Aeronautics and Space Admin is t ra t ion  
Lewis Research Center 
Cleveland, Ohio 44135 
SUMMARY 
J 
D i r e c t  o p t i c a l  c o n t r o l  o f  microwave/mi l l imeter wave devices can prov ide  
f a s t e r  swi tch ing,  ga in  and phase a d j u s t a b i l i t y  i n  a m p l i f i e r s ,  and frequency 
t u n i n g  o r  l o c k i n g  i n  o s c i l l a t o r s  ( r e f .  1). Furthermore, i t  can reduce the  
c complex i ty  o f  f i b e r  o p t i c  s igna l  d i s t r i b u t i o n  networks f o r  Gall ium-Arsenide 
(GaAs) Mono l i t h i c  Microwave In tegra ted  C i r c u i t  (MHIC) based phased-array 
antennas f o r  f u t u r e  space communication system. 
Several  authors have inves t i ga ted  t h e  pho tovo l ta i c  and photoconduct ive 
e f f e c t  of l i g h t  on the  dc c h a r a c t e r i s t i c s  and the  equ iva len t  c i r c u i t  parameters 
o f  GaAs s ing le-gate Metal  Semiconductor F i e l d  E f f e c t  Trans is to rs  (MESFETs) 
( r e f s .  1 and 2 ) .  However, t he  s ing le-gate MESFET has severa l  l i m i t a t i o n s .  
I 
cr) 
03 
m 
I w 
c 
This  paper presents computed r e s u l t s  on l i g h t  induced vol tage, V l i t ,  and 
I t s  e f f e c t  on the  dc c h a r a c t e r i s t i c s  o f  bo th  the  GaAs dual-gate MESFET and the  
GaAs Permeable Base T rans i s to r  (PBT). The dual-gate MESFET when compared w i t h  
t h e  s i n g l e  gate MESFET has found a wide v a r i e t y  o f  app l i ca t i ons .  T h i s  i s  so 
because o f  t he  presence o f  t w o  independent c o n t r o l  gates together  w i t h  excel-  
l e n t  i s o l a t i o n  c h a r a c t e r i s t i c s .  The PBT on the  o ther  hand has a much h igher  
f i g u r e  o f  m e r i t ,  t h a t  i s ,  the  maximum frequency o f  o s c i l l a t i o n .  Typ ica l l y ,  t h e  
f i g u r e  o f  m e r i t  o f  a PBT i s  150 GHz as compared t o  60 GHz f o r  GaAs MESFET. 
Hence, PBTs can operate a t  a much higher speed than MESFETs. 
l a s e r  t o  the  a c t i v e  reg ion,  o f  a dual-gate MESFET and o f  a PBT, through an 
i n t e g r a t e d  o p t i c a l  waveguide and an o p t i c a l  f i b e r  respec t i ve l y .  L i g h t  i s  
respons ib le  f o r  t h e  generat ion o f  excess e lec t ron-ho le  p a i r s  i n  the  a c t i v e  
reg ion;  which i n  t u r n  increases the  m i n o r i t y  c a r r i e r  concentrat ion,  t h a t  i s ,  
holes i n  a n-type channel. An expression f o r  t h e  l i g h t  induced vo l tage V l i t  
as a f u n c t i o n  o f  t he  m i n o r i t y  c a r r i e r  concent ra t ion  and o ther  phys i ca l  proper-  
t i e s  o f  GaAs i s  g iven  i n  re ference 3. 
Figure  1 i s  a schematic diagram i l l u s t r a t i n g  the  coup l ing  o f  l i g h t  f rom a 
An expression r e l a t i n g  d r a i n  cur ren t ,  Ids,  t o  the  app l i ed  gate te rmina l  
vol tages, Vgsl 
mina t ing  e i t h e r  o f  t he  two gates o f  a dual-gate MESFET i s  equ iva len t  t o  forward 
b i a s i n g  t h a t  gate by a vo l tage source equal t o  V l i t .  The n e t  vo l tage a t  
t h a t  ga te  i s  t he re fo re  a superposi t ion o f  t h e  ga te  te rm ina l  vo l tage and V l i t .  
An expression r e l a t i n g  d r a i n  cu r ren t  dens i t y  t o  t h e  app l i ed  ga te  b i a s  
V S ,  and vds 
T j e  n e t  vo l tage a t  t he  gate i s  a superpos i t ion  of Vgs and V l i t .  
and V 2, and the d ra in  t o  source vo l tage,  Vds, f o r  a 
depletion-mode (normal 9 y-ON) dual-gate MESFET i s  g iven i n  re ference 4. I l l u -  
3 
f o r  a permeable-base t r a n s i s t o r  1 s  g iven  i n  re fe rence 5. 
*NRC-NASA Research Associate. 
The dual-gate MESFET a c t i v e  l a y e r  th ickness,  t h e  PBT a c t i v e  l a y e r  t h i c k -  
ness and t h e i r  respec t ive  doping d e n s i t i e s  a re  i n d i c a t e d  i n  f i g u r e  1. 
i n t r i n s i c  c a r r i e r  concent ra t ion  and the  m i n o r i t y  c a r r i e r  l i f e  t ime are  
1 .79~106 cm3 and 10-8 sec respec t i ve l y .  
11 h t  and the  o p t i c a l  absorp t ion  c o e f f i c i e n t  i n  GaAs a re  normal ly  0.87 pm and 
The 
The wavelength o f  t h e  i n c i d e n t  
IO 4 cm-1 respec t ive ly .  
Using these equations l i g h t  induced vo l tages a r e  computed f o r  t he  dual -  
ga te  MESFET and the PBT as a f u n c t i o n  of t he  i n c i d e n t  o p t i c a l  power dens i ty .  
Th ls  i s  shown i n  the  i n s e t  i n  f i g u r e  2. The l i g h t  induced vo l tage i s  observed 
y w i t h  the  i n c i d e n t  o p t i c a l  power dens i ty .  Besides, t h e  two 
equa l ly  s e n s i t i v e  t o  l i g h t .  
t o  increase l i n e a r  
devices a re  almost 
The computed 
gate 2 o p t i c a l l y  i 
by 16 mA w i t h  gate 
and 
Vd c 
I d s  o f  t he  dual-gate MESFET as a f u n c t i o n  o f  vds, w i t h  
luminated, i s  shown i n  f i g u r e  2. Fur ther ,  I d s  increases 
1 o p t i c a l l y  i l l u m i n a t e d  (1 pW/cm2) and V s1 = -1.5 V 
Vg2 = OV.  The computed d r a i n  cu r ren t  dens i t y  3 as a ?unct ion o f  
f o r  a PBT when the  gate g r a t i n g  i s  i l l u m i n a t e d  i s  shown i n  f i g u r e  3. 
The dual  gate MESFET provides a d d i t i o n a l  c o n t r o l  due t o  t h e  presence o f  two 
independent c o n t r o l  gates w h i l e  the  PBT can handle a much h igher  c u r r e n t  
dens1 t y  . 
REFERENCES 
1. R.G. Hunsperger, "Opt ica l  Contro l  o f  Microwave Devices," i n  In ter r ra ted 
Op t i ca l  C i r c u i t  Engineer ing 11, SPIE, Vol. 578, S. Sriram, ed., Bell ingham: 
SPIE, 1985, pp. 40-45. 
2. A.A.A. DeSalles, "Opt ica l  Contro l  o f  GaAs MESFET's," I E E E  Trans. Microwave 
Theory Tech., vo l .  HTT-31,pp. 812-820, Oct. 1983. 
3. 6.3. Chaturvedi, R.K. Puroh i t  and B.L. Sharma, l lOptical E f f e c t  on GaAs 
MESFET's," I n f r a r e d  Phys., vo l .  23, pp. 65-68, 1983. 
4. R.A. Minasian, "Model l ing DC Charac te r i s t i cs  o f  Dual-Gate GaAs MESFET's," 
IEE Proc. Pa r t  I: So l id -s ta te  E lec t ron  Devices, vo l .  130, pp. 182-186, 
Aug. 1983. 
5. W.R.Frensley, "An Ana ly t i c  Model f o r  t he  Bar r i e r -L im i ted  Mode o f  Operat ion 
o f  t he  Permeable Base Trans is tor , '  I E E E  Trans. E lec t ron  Devices, vo l .  Ed-30, 
pp. 1624-1628, Dec. 1983. 
2 
, 
,- TO GaAs LASER 
OPTICAL WAVEGUIDE ,’ OR OPTICAL FIBER 
CARRYING LIGHT I 
ILLUMINATING 
T = 0 5 5  pm 
LSEMl INSULATING 
GaAs SUBSTRATE 
~ = l p r n  I 
W = 300 prn 
GATE CONTACT 7, 
,- OPTICAL FIBER 
/I GATE FROM TOP 1 ILLUMINATING SCHOTTKY 
GATE FROM SIDE 
SOURCE 
CONTACT 
CD-86-18370 
Figure 1. - Schematic diagram i l lus t ra t ing (a) a n  optical waveguide i l l u m i n a t i n g  a dual-gate 
MESRT. (bl a n  optical f iber i l l umina t ing  a permeable base t rans is to r  at two possible locations. 
DUAL-GATE GaAs MESFET 
VGSl = -1.5 v 
vG2 = -1.0 v 
/ \ WITH 0.87 rrn ILLUMINATION ON GATE 2 ,  P, W/cm2 GaAs 
10-3 
GaAs MESFET 
I/ 
ff 
WITHOUT ILLUMINATION 
LIGHT 
INDUCED , 
voL-'-- 
0- 
10-12 10-9 10-6 10-3 
PER UNIT AREA, P, W/crn2 
OPTICAL POWER INPUT 
1 2 3 
DRAIN VOLTAGE, VDS, V - 4 
Figure 2 - Drain current versus drain to source voltage with gate 2 illuminated for a dual- 
gate MESAT. Also shown in inset i s  the light induced voltage as a function of the in- 
cident optical power. 
loo Oo0 F 
GaAs PERMEABLE BASE TRANSISTOR 
WITH 0.87 am ILLUMINATION, P ( W k d )  
10-6 
0 .5 1 1.5 2 2.5 .01 
DRAIN VOLTAGE, VDS, V - 
Figure 3. - Drain current density versus drain to source voltage 
with gate il lumination for a permeable base transistor. 
1. Report No. 12. Government Accession No. 
17. Key Words (Suggested by Author@)) 
NASA TM-88823 
4. Title and Subtitle 
18. Distribution Statement 
Optically Controlled GaAs Dual-gate MESFET and 
Permeable Base Transistors 
19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of pages 
Uncl ass1 f i ed Unclassified 
7. Author@) 
R.N. Simons and K.B. Bhasin 
22. Price' 
9. Performing Organization Name and Address 
National Aeronautics and Space Administration 
Lewis Research Center 
Cleveland, Ohio 44135 
National Aeronautics and Space Administration 
Washington, D.C. 20546 
12. Sponsoring Agency Name and Address 
15. Supplementary Notes 
3. Recipient's Catalog No. 
5. Report Date 
6. Performing Organization Code 
506-44-21 
8. Performing Organization Report No. 
E-31 83-1 
IO. Work Unit No. 
11. Contract or Grant No. 
13. Type of Report and Period Covered 
Technical Memorandum 
14. Sponsoring Agency Code 
Prepared for the Conference on Lasers and Electro-Optics (CLEO) cosponsored by 
the Institute of Electrical and Electronics Engineers and the Optical Society of 
America, San Francisco, California, June 9-13, 1986. 
16. Abstract 
Optically induced voltage and dc characteristics of the GaAs Dual-gate MESFET and 
the Permeable Base Transistor (PBT) wlth optical illumination at wavelength below 
0.87 pm were obtained and compared with GaAs MESFET. 
can handle higher current density when illuminated. 
It was observed that PBT 
Microwave devices 
Optical .control 
GaAs Dual-gate MESFET 
GaAs permeable base transistor 
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Optically controlled GaAs dual-gate MESFET and permeable base transistors

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