868 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 11, NO. 7, JULY 1999 Millimeter-Wave Long-Wavelength Integrated Optical Receivers Grown on GaAs Yves Baeyens, Member, IEEE, Andreas Leven, Student Member, IEEE, Wolfgang Bronner, Volker Hurm, Ralf Reuter, Klaus K¨ ohler, Josef Rosenzweig, and Michael Schlechtweg, Member, IEEE Abstract— Compact monolithically integrated narrow-band photoreceivers with a high responsivity at millimeter-wave frequencies were realized. In these receivers, a 1.3–1.55- m wavelength In Ga As p-i-n photodiode, grown lattice relaxed on GaAs, is conjugately matched to a two-stage narrow-band amplifier based on 0.15- m GaAs based dual-gate PHEMT’s. A first receiver, designed for operation around 42 GHz, obtains an optical responsivity of 7 A/W. This is a 38-dB increase in comparison with the measured responsivity of a terminated p-i-n photodiode. For a second receiver, operating at 58 GHz, a responsivity of 2.5 A/W is obtained. These receivers are, to our knowledge, the first high-gain millimeter-wave long-wavelength photoreceivers monolithically integrated on GaAs. Their high responsivity makes them attractive for use in various microwave and millimeter-wave-over-fiber applications. Index Terms—Integrated optoelectronics, millimeter-wave FET amplifiers, MIMIC’s, MODFET amplifiers, photodetectors. I. INTRODUCTION A NUMBER of wide-band networks combining both millimeter-wave (mm-wave) and optical techniques were recently proposed [1], [2]. By performing the upconversion of the baseband data to the mm-wave carrier frequency in the control station and by transporting the mm-wave modulated signal over optical fiber, no local oscillators or mm-wave modulators are required in the basestations. This allows to reduce the complexity and cost of basestations used in systems such as microwave video distribution at 42 GHz or wireless LAN’s operating up to 60 GHz [2]. The commercial insertion of such mm-wave-over-fiber systems requires high performance and cost-effective narrow-band photoreceivers. Monolithic optoelectronic integrated circuits (OEIC’s) are attractive because of their lack of bonding parasitics, com- pactness and potential cost reduction. A number of mono- lithic integrated photoreceivers were reported in the litera- ture. A monolithic GaAs-based high-electron mobility transis- tor (HEMT)/metal–semiconductor–metal (MSM) photodiode (PD) OEIC receiver was reported in [3]. This OEIC receiver shows an 18 dB improvement of the optical link gain at 48 GHz compared with that of the MSM itself. This detector Manuscript received March 10, 1999; revised March 26, 1999. Y. Baeyens was with Fraunhofer-Institute for Applied Solid-State Physics, D-79108 Freiburg, Germany. He is now with Lucent Technologies, Bell Laboratories, Murray Hill, NJ 07974 USA. A. Leven, W. Bonner, V. Hurm, R. Reuter, K. K¨ ohler, J. Rosenzweig, and M. Schlechtweg are with Fraunhofer-Institute for Applied Solid-State Physics, D-79108 Freiburg, Germany. Publisher Item Identifier S 1041-1135(99)05170-8. Fig. 1. Cross section of an InGaAs p-i-n PD integrated with a GaAs-based PHEMT. Fig. 2. Circuit diagram of the 42-GHz p-i-n–HEMT receiver. operates at 0.8- m wavelength, limiting its application mainly to short haul. Most long-wavelength photoreceivers need to be integrated on an InP substrate. Recently, two narrow-band photoreceivers combining an MSM PD with a three-stage InP- based HEMT MMIC amplifier and with a responsivity of 3.5 A/W at 38 GHz [4], and 0.9 A/W at 57 GHz [5] were reported. In this letter, we report two fully integrated GaAs-based mm-wave OEIC photoreceivers. A first receiver was de- signed for wireless broadcast applications at 42 GHz [6], a second receiver for wireless local area networks (LAN’s) operating at 60 GHz. Both receivers use a 1.3–1.55 m wavelength In Ga As p-i-n PD, grown lattice relaxed on GaAs, which is conjugately matched to a two-stage monolithic microwave integrated circuit (MMIC) amplifier based on 0.15- m GaAs based dual-gate PHEMT’s. II. TECHNOLOGY AND FABRICATION For the detection of light with a wavelength between 1.3–1.55- m InGaAs absorption layers, usually grown lattice matched on InP, are required. GaAs as a substrate 1041–1135/99$10.00  1999 IEEE