IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES,VOL. 49, NO. 10, OCTOBER 2001 1921 Ultrahigh-Speed InP/InGaAs DHPTs for OEMMICs Hideki Kamitsuna, Member, IEEE, Yutaka Matsuoka, Member, IEEE, Shoji Yamahata, Member, IEEE, and Naoteru Shigekawa Abstract—This paper presents an ultrahigh-speed InP/InGaAs double-heterostructure phototransistor (DHPT) with a record optical gain cutoff frequency of 82 GHz. This excellent perfor- mance originates from the double-heterostructure’s compatibility with high-performance double-heterostructure bipolar transistor (DHBT) and a new self-aligned process. To demonstrate the excellent performance of the DHPT, two kinds of optoelectronic MMICs (OEMMICs) were designed and fabricated. One is a 40-GHz-band DHPT/DHBT photoreceiver that shows the DHPT’s ability to be simultaneously integrated with a high-performance DHBT. The 40-GHz operation frequency is also the highest reported for monolithically integrated HPT/HBT photoreceivers. The other is a direct optical injection-locked oscillator that can extract an electrical clock signal from optical data streams. The OEMMICs are promising for compact and low-power-consump- tion optical receivers on an InP platform for millimeter-wave photonics and ultrahigh-speed optical communication systems. Index Terms—HPT, MMIC, OEIC, optical injection-locked os- cillator, photoreceiver. I. INTRODUCTION C OMPACT, high-speed, and cost-effective optical transponders that consume little power have become increasingly important for optical communication systems, including microwave photonics systems [1]. One of the most desirable pieces of hardware is an optical transceiver that con- sists of both optical and electronic devices on a semiconductor substrate, namely, an InP platform. In a microwave photonics system, an optical/microwave con- verter is required for radio base stations. One of the most de- sirable configurations is to use just a photodetector plus an- tenna. A UTC-PD [2] combined with an optical fiber pream- plifier makes it possible to eliminate an electrical postamplifier. However, a configuration of a photodetector plus an electrical amplifier without an optical preamplifier is still attractive, es- pecially for low-cost subscriber systems. Therefore, it is still important to develop an integrated microwave/millimeter-wave photoreceiver. In an IF transmission scheme with an LO oscil- lator in a radio base station [3], an optoelectronic mixer is a key device. A phototransistor is one of the most promising devices for this type of application. Manuscript received December 26, 2000; revised May 18, 2001. H. Kamitsuna and N. Shigekawa are with the NTT Photonics Laboratories, Atsugi, Kanagawa 243-0198, Japan (e-mail: kamituna@aecl.ntt.co.jp). Y. Matsuoka was with the NTT Photonics Laboratories, Atsugi, Kanagawa 243-0198, Japan. He is now with Anritsu Corporation, Atsugi, Kanagawa 243- 0855, Japan. S. Yamahata was with NTT Photonics Laboratories, Kanagawa 243-0198, Japan. He is now with the NTT Electronics Corporation, Machida, Tokyo 194- 0004, Japan. Publisher Item Identifier S 0018-9480(01)08700-2. In multigigabit-per-second optical transmission systems, a 3R (regenerating, reshaping, and retiming) optical receiver is utilized. In this receiver, a clock recovery circuit that can ex- tract a clock signal from transmitted data streams is a key com- ponent. The conventional fully electrical configuration usually exploits a phase-locked loop that consists of a voltage control oscillator, phase comparator, and low-pass filter. If an electrical oscillator with an optical input port, i.e., a direct optical injec- tion-locked oscillator [4] can be applied to a clock recovery cir- cuit, we can extremely simplify the configuration and reduce power consumption. For a direct optical injection-locked oscil- lator application, not only an excellent photodetection charac- teristic but also excellent microwave performance that can gen- erate an oscillation is required for a phototransistor. In this ap- plication, a phototransistor is one of the most promising devices. In both systems, ultrahigh-frequency analog circuits and/or ultrahigh-speed digital circuits are also required. Therefore, we must develop a high-performance phototransistor that is compatible with a high-performance transistor. A number of InP-based phototransistors [5]–[8] have been studied to date. Among these phototransistor structures, layer- and process-compatible heterojunction phototransistors (HPTs) based on heterojunction bipolar transistor (HBT) technology are the most promising for high-performance monolithically integrated photoreceivers [6]–[8]. Unfortunately, however, the measured and designed operation frequency of monolithically integrated HPT/HBT photoreceivers remains below 28 GHz [7], [8] and millimeter-wave (over 30 GHz) operation has never been reported to date. This is because high-speed HPTs for millimeter-wave application require both extremely high-speed base/collector photodiode operation and high maximum oscil- lation frequency ( ) of a transistor. This paper presents an InP/InGaAs double-heterostructure phototransistor (DHPT) with a record optical gain cutoff frequency of 82 GHz. This performance is suitable for mil- limeter-wave photodetector and optically injection-locked oscillator applications. Such excellent performance comes from: 1) the elimination of low-speed holes by using the double-heterostructure; 2) high unity current gain cutoff fre- quency ( ); and 3) high- through device size reduction by using a self-aligned process. To demonstrate the excellent per- formance of the DHPT, this paper also presents a 40-GHz-band optoelectronic millimeter-wave monolithic integrated circuit (OEMMIC) photoreceiver utilizing ultrahigh-speed DHPTs and double-heterostructure bipolar transistors (DHBTs). In addition, a direct optical injection-locked oscillator that can extract an electrical clock signal from optical data streams is presented. 0018–9480/01$10.00 © 2001 IEEE