A 10 Gbit/s monolithic integrated optoelectronic receiver has been fabricated with a metal-semiconductor-metal (MSM) photodiode and enhancement/depletion 0.5 &#956;m recessed-gate AlGaAs/GaAs HEMTs. A -3 dB bandwidth of 11.3 GHz has been achieved

Axmann, Albert

Benz, Willi

Berroth, Manfred

Hurm, Volker

Hülsmann, Axel

Kaufel, Gudrun

Köhler, Klaus

Ludwig, Manfred

Osorio, Ricardo

Raynor, Brian

Rosenzweig, Josef

Schneider, Joachim

Online Publikationen der Universität Stuttgart

Microelectronic Engineering 15 (1991) 275-278 275 
Elsevier 
10 Gbit/s Monolithic Integrated Optoelectronic Receiver using an MSM Photo-
diode and AIGaAs/GaAs HEMTs 
Y. Hurm, J. Rosenzweig, M. Ludwig, A. Axmann, W. Benz, M. Berroth, R. Osorio, 
A. Hillsmann, G. Kaufel, K. Kohler, B. Raynor, and Jo. Schneider 
Abstract 
Fraunhofer-Institut fUr Angewandte Festkorperphysik , 
Tullastr. 72, D-7800 Freiburg, Germany 
A 10 Gbit/s monolithic integrated optoelectronic receive r has been fabricated with a metal-
semiconductor-metal (MSM) pholodiode and enhancement/depletion 0.5 f.1.m recessed-gate AI-
GaAs/GaAs HEMTs. A -3 dB bandwidth of 11.3 GHz has been achieved. 
1. DESIGN AND FABRICATION 
Several research groups have reported on the technology of monolithic in tegration of MES-
FETs on GaAs with photodetectors for light of wavelength 0.85 ~m [1,2]. ln this paper we present 
the firs t pholoreceiver which is based on an MSM pholodiode and A1GaAs/GaAs HEMTs (3]. 
The photoreceiver was fabricated using our es tablished 0.5 ~lm recessed-ga te process for double 
delta-doped qua ntum well HEMTs [4,5]. Now Ihis standard process includes MSM photodiodes . 
E-FET O-FET N" 
GU~ 30 nm 3 , 1018 em-3 
AlGa.l a 3 ." I" GaA.~ 7 . 5 nm 1017 elll- J A.lGaAa 3 ." 
Isl IDl Isl liola I I I EtCh-Sto 
1m EtCh-Sto 
GaA.~ 6 ." 
A1GaA.s J . 3 nm 
10 12 em-2 GilA, 1 . 7 nlll . , Delta-Do In 
AlGIIAS 3 . 3 nm 
I I I 2-DEG Channe I I GaolS 15 nm 
AlGUs 5 ." 1012 ~m-2 GaolS 1. 7 tim 2.5 ~ Dlllta-Do In 
MSM-PO I .lIGII""'! 200 nm 
Su erlattle!! 
rMlrMl Buf fer GaA.s 300 nil' 
Substrllte Ga Aa 
Figure 1. Schematic cross section of an MSM pholodiode integrated with enhancement and 
depletion AIGaAs/GaAs HEMTs. 
0167·9317/91/$3.50 © 1991 - Elsevier Science Publishers BY All rights reserved. 
276 V Hunn et al. /10 Gbit/s monolithic integrated optoelectronic receiver 
" , 
1 I< Or. ... 
,"s ... -PO 
40 1-'"' 
q 
'''" 
500 On", 
J , 
T 
'0 ,. r 
1 k Oh... ~ 
~ 
-, , 
80 1-'"' 
~ 
80 I)"' 
Fieure 2. Circuit diagram of the pho-
tOreceiver. The receiver consists of 
an MSM photOdiode, a transimpe-
dance amplifier with fWe enhance-
ment transistors and three NiCr thin 
film resistors, and an output buffer 
with two deplet ion transistors. 
Fieure 3. Photograph of the 
fabricated pholoreceiver. The 
depicted chip area measures 
500x350 flm2. The MSM 
photodiode at the left side has 
an active area of 25x25 flm2. 
Figure 1 shows a cross-section of an MSM photodiode integrated with enhancement and de-
pletion type transistors. The vertical structure was grown on the semi-insulating GaAs substrate 
by molecular beam epitaxy [4]. The AlAs mole fraction of the A1GaAs layers was 0.3. By means 
of etch SlOps and a selective reactive ion etch process, exact control of the transistor threshold 
voltages was obtained [SJ. The site of the MSM photodiode was etched down to the undoped 
buffer layerby a wet etch prior to the fabrication of the photodiode fingers. The 1 lAm wide fingers 
with a 1.5 lAm separation were defined by electron beam lithography and subsequent evaporation 
and lifl-Qff of Ti/Pt/Au metal. 
As shown in Figures 2 and 3 the pholoreceiver consists of an MSM photodiode, a transimpe-
dance amplifier with a 500 Q feedback resistor, and an output buffer. Airbridges connect the pho· 
todiode to the electric circuit. The layout also includes blocking ca pacitors for the supply volta-
ges. 
2. DEVICE AND CIRCUIT PERFORMANCE 
Figure 4 shows the curren t-voltage characteristics of an MSM photodiode irradiated by light 
of various intensities at a wavelength of 0.84 ~m. The DC responsivities of the photodiode were 
~ 200 
~ 100 
• L 
'; 0 
u 
o 
~ - 100 
o 
~ 
• 
• < 
0 
0 
• 
• 
• 
• > 
-• 
-200 
>, 
>, 
0:; -9 
• 
-; 
.-< 0 
., 
L < L , 
, 
u~ 
-; 
· -~o 
., 
-> 
~ , 
~o 
ru 
V Hunn et al. /10 Gbit/s monolithic integrated opLOelectronic receiver 277 
-8 
, 
-4 0 
Voltage 
, 
RG32-68 2582 
4 
[V ) 
8 
710 
520 
330 
1'0 
(\JWI 
OptIcal 
Power 
RG31-I05 2SBI-3001N5 
, , 
" 
Figure 4. Current- voltage charac-
teristics of an MSM photod iode 
for different intensity of the laser 
diode irradiation . 
Fi gure 5. Measured frequency re-
sponse of the photorece ive r. The 
measured - 3 dB bandwidth lies at 
8.2 GHz. 
F'reQlIenq lGHZJ 
RG31-105 2581-30DIN5 
( 50 DS/div] 
Fi2ure 6. Eye diagrams of 
the laser d iode current and 
the pholorece iver output 
voltage for a 10 Gbit/s NRZ 
pseudora ndom da ta stream 
(same photo receiver as that 
in Fig. 5). 
0.25 NW for 4 V and 0.27 NW for 10 V bias. The da rk current at 4 V was 2 nA for an active area 
of25x2S f1 m2. The following mean values for the enhancement and depletion HEMT parame-
ters, respectively, have been Obtained: threshold voltage::: 0.1 and -0.5 V, tra nsconductance = 
500 and 390 mS/mm, source resistance = 0.7 and 0.6 Qmm, transit frequency::: 35 and 30 GHz. 
AJI high frequency measu rements of the receiver were performed on-wafer using CASCA-
DE probes . The photodiode was irradiated by 0.84 f1m light from a highspeed ORTEL laser diode 
via a single mode fiber. The current driving the laser diode was modulated to obtain up to 0.8 m W 
peak-ta-peak modula ted optical signa!s. The relative response versus frequency, measured al 
278 V Hu.m~ et al. f 10 Gbitfs monolithic illtegrated optoelectronic receiver 
0; 
" 
, 
• 
• < ) 0 
0 
• 
• < 
• 
0 , 
-• 
• 
-) 
< 
-, 
0 
RG32-6B 2SBI-30D IN5 
_ 0 0 _ ' --"-o~y~~ 
-- 0 0 " 0", 
2 • , , 
Fr eque nc y \GHz l " 
Fiiure 7. Measured frequency re-
sponse of a photoreceiver from a 
different wafer (RG32--68). The 
measured -3 dB bandwidth lies at 
11.3 GHz. 
the output of a photoreceiver (wafer RG31-1 05), is shown in Figure 5. The -3 dB bandwidth o f 
the pholoreceiver for sinuso idal modu lated incident light lies at 8.2 GHz. The frequency respon-
se of the ORTEL laser diode itself was determined using a calibrated GEe photodiode. The cir-
cuit response to pulse-modulated non-relum-to-zero (NRZ) optical signals was tes ted at data 
ra les up to 10 GBitls by means of an ANR ITSU pulse pattern genera tor. The eye diagrams of the 
laser diode current and the photo receiver outpu t voltage demonstrate (Figure 6) that the optoelec-
tron ic receiver operates successfully for a 10 Gbills NRZ pseudorandom data stream of length 
27_1 bits. Eye diagrams of the same quality were observed for the data stream length 231_1 bits. 
Figure 7 shows the relative response versus frequency of a photoreceiver from a different wa-
fer (RG 32--68) from that in Figures 5 and 6. For this wafer the threshold vo ltages are 0 and -0.7 V 
fo r the enhancement and depletion HEMTs, respec tively. Due 10 the different opera ting point of 
the transimpedance amplifier the effective transimpedance of the photoreceiver was 330 Q in-
stead of 440 n, i.e. the output voltage was 25 % lowe r. Furthermore, the frequency response is not 
as flat as that of the firs t photoreceiver, however, the - 3 dB bandwidth lies a t 11.3 GH z. 
ACKNOWLEDGEMENT 
The financial support of the Bundesministerium flir Forschung und Technologie through the 
CAE-project NT2778A is gratefully acknowledged. Spec ial thanks go to H.S. Rupprecht for hi s 
continuous encouragement. 
REFERENCES 
[1] C.S. Harder, B. Van Zeghbroeck, H. Meier, W. Patrick, and P. Vetliger, 
IEEE Electron Device Let!. , vol. EDL-9, pp. 171 - 173, 1988. 
[2] H. Hamaguchi, M. Makiuc hi , T. Kumai, and O. Wada, 
IEEE Electron Device Let!. , vo l. EDL--8, pp. 39-41, 1987. 
[3] V. Hurm, J. Rosenzweig, M. Ludwig, W. Benz, M. Berroth, A. Hulsmann, 
G. Kaufel , K. Kohler, B. Raynor, and J. Schneider, 
Electron. Leu., vol. 27, pp. 734-735,1991. 
[4] K. Kohler, P. Ganser, K. H. Bachem, M. Maier, J . Hornung, and A. Hulsmann, 
Proc. lnt. Symp. CaAs and Related Compounds , Jersey, 1990, Ins!. Phys. Conf. Ser. , 
vol. 112, pp. 521 - 526, 1990. 
[5] A. Hlilsmann, G. Kaufel , K. Koh ler, B. Raynor, 1. Sc hne ider, and T. lakobus, 
lpn. l . Appl. Phys. , vol. 29, pp. 23 17-2320,1990. 


10 Gbit/s monolithic integrated optoelectronic receiver using an MSM photodiode and AlGaAs/GaAs HEMTs

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10 Gbit/s monolithic integrated optoelectronic receiver using an MSM photodiode and AlGaAs/GaAs HEMTs

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