IEEE JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL.??, NO.??, MONTH YEAR 1 InP/InGaAs Single HBT Technology for Photoreceiver OEIC’s at 40 Gb/s and Beyond D. Huber, R. Bauknecht, C. Bergamaschi, M. Bitter, A. Huber, T. Morf, A. Neiger, M. Rohner, I. Schnyder, V. Schwarz, and H. J¨ ackel Abstract— We describe an advanced InP/InGaAs based technology for the monolithic integration of pin-photodiodes and SHBT-transistors. Both devices are processed using the same epitaxial grown layer structure. Employing this technology, we have designed and fabricated two pho- toreceivers achieving transimpedance gains of / and opti- cal/electrical bandwidths of / . To the best of our knowl- edge, this is the highest bandwidth of any HBT-based photoreceiver OEIC published to date. We even predict a bandwidth of for the same circuit topology by a simple reduction of the photodiode diameter and an adjustment of the feedback resistor value. Keywords—Transimpedance amplifier, Photoreceiver, OEIC,HBT, InP, Processing I. I NTRODUCTION Photoreceiver circuits are key-components in fibre optic transmission systems. The exponentially growing demand for higher data rates makes bandwidth to the most important fig- ure of merit for such OEIC, whereas sensitivity and gain have become a slightly lower priority due to the introduction of Er- bium doped fiber amplifiers (EDFA’s). Being the first ampli- fication stage in a chain, the noise figure of the optical am- plifier dominates the overall sensitivity of the system. In ad- dition, optical gains of and more achieved by EDFA’s relax the gain requirements for following electrical stages. Fig- ure 1 shows a comparison of published receiver performances in terms of optical/electrical bandwidth and conversion gain. Be- cause the conversion gain is the product of transimpedance gain and photodiode-responsivity, it characterizes the entire receiver OEIC and not only the preamplifier as the transimpedance gain does. HEMT’s and HBT’s are both promising candidates to push receiver bandwidths up to and beyond [1], [11] (Fig. 1). In general, the high frequency noise behaviour of HEMT’s is better enabling potentially higher sensitivities of such receivers. However, reported highest values are com- parable for both technologies: at for HBT-OEIC [8] and at for HEMT-OEIC [12], [17], re- spectively. Furthermore, the minimum dimensions of HEMT’s (gate width) are much smaller than the minimum emitter width of comparable HBT’s leading to more relaxed lithography re- quirements for the HBT fabrication. And the gate threshold volt- Manuscript received ???, revised ??? D. Huber, A. Huber, T. Morf, A. Neiger, M. Rohner, I. Schnyder, V. Schwarz and H. J¨ ackel are with the Electronics Laboratory, Swiss Federal Institute of Technology Z¨ urich (ETHZ), Gloriastr. 35, CH-8092 Z¨ urich, Switzerland M. Bitter is with the Institute of Quantum Electronics, Micro- and Optoelec- tronics Laboratory, CH-8093 Z¨ urich, Switzerland C. Bergamaschi is with the Fachgruppe f¨ ur angewandte Schaltungstechnik, FH Aargau, CH-5210 Windisch, Switzerland R. Bauknecht is with Opto Speed SA, Via cantonale CH-6805 Mezzovico, Switzerland 5 10 15 20 25 35 40 45 50 55 bandwidth f, GHz HEMT Receiver Multistage Receiver 30 NTT 98 [12] conversion gain, V/W 10 10 3 2 this work ETH 99 [2] ETH 98 [3] RIT 97 [5] RIT 97 [5] RIT 97 [5] ETH 99 [7] NTT 98 [13] HHI 99 [15] FHI 98 [14] ETH 96 [16] FHI 97 [19] NTT 96 [6] ETH 99 [4] HBT Receiver NTT 99 [11] Packaged Module UND 98 [17] [1] FHI 98 [18] Fig. 1. Comparison of published optical/electrical receiver performances age variation of HEMT’s is higher than the base-emitter voltage variation of bipolar junction transistors resulting in a more diffi- cult bias-point control of HEMT-based circuits. The InP/InGaAs material system in combination with a SHBT technology offers the option to use the base-collector ho- mojunction of the transistor also for the formation of the pho- todiode [9]. Two advantages are the consequence of this tech- nique: The layer structure of both devices can be grown in one step avoiding a regrowth process with its problems. In addi- tion, the diode fabrication process can be fully incorporated into the transistor fabrication. The drawback of fabrication simplic- ity is a speed limiting trade off (collector layer thickness) be- tween diode depletion layer capacitance and transistor transit time. However, it is the purpose of this work to show the poten- tial of this simple approach to reach data-rates up to . Whereas most HEMT-based receivers operating above are traveling wave amplifiers (TWA) [11], [12], [13], [14], [15], HBT-based amplifiers are mainly lumped circuits [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], because trav- eling wave designs are more difficult to realize with HBT’s due to the resistive small-signal behaviour of their base emit- ter junction. Although reported electrical bandwidths of TWA’s achieve frequencies above [20], best values for op- tical/electrical measured bandwidths are not only reached by monolithic HEMT/TWA designs [11], but also by monolithic, lumped HBT designs [1] (Fig. 1). Disadvantages of distributed circuits are their much higher chip area consumption and the fact that their reported transimpedance gains are currently around [11], [12], [13], [14], [15]. This is clearly lower than the corresponding gain of or even reported in [2] and in this work.