222 IEEE MICROWAVE AND GUIDED WAVE LETTERS, VOL. 7, NO. 8, AUGUST 1997 An InP HEMT W-Band Ampliﬁer with Monolithically Integrated HBT Bias Regulation K. W. Kobayashi, Member, IEEE, H. Wang, Senior Member, IEEE, R. Lai, L. T. Tran, T. R. Block, P. H. Liu, J. Cowles, Member, IEEE, Y. C. Chen, T.-W. Huang, A. K. Oki, Member, IEEE, H. C. Yen, and D. C. Streit, Senior Member, IEEE Abstract—This paper presents the results of the ﬁrst W-band InP-based high electron mobility transistor-heterojunction bipo- lar transistor (HEMT-HBT) monolithic microwave integrated circuit (MMIC). The InP-based HBT and HEMT devices are monolithically integrated using selective molecular beam epitaxy (MBE). The ampliﬁer demonstrates the highest frequency perfor- mance MMIC so far obtained with this technology. A single-stage HBT op-amp current regulator is integrated with a single-stage HEMT ampliﬁer in order to regulate and self-bias the HEMT device over process, temperature, and age variations. The HBT regulates the HEMT dc bias to within 3% of the bias current while consuming only a small fraction of the total dc power. The HEMT W-band ampliﬁer achieves a radio frequency (RF) gain of 8.25 and 5.9 dB at 77 and 94 GHz, respectively. A minimum noise ﬁgure of 4.2 dB was also recorded at 93.5 GHz. The RF performance achieved from the HEMT ampliﬁer using the InP- based HEMT-HBT integrated technology is comparable to that of InP-based single-technology HEMT performance. Index Terms— HBT, HEMT, monolithic integration, selective epitaxy. I. INTRODUCTION W HILE the application of monolithic microwave inte- grated circuits (MMIC’s) has generally resulted in a reduction in size, weight, and cost of the integrated microwave assembly by consolidating several circuit functions on a single semiconductor chip, there is a limit to the number of circuit functions which can be integrated with a single-device IC tech- nology and still maintain optimum performance. For example, the low-noise and high-frequency properties of HEMT’s make them ideal for low-noise and millimeter-wave ampliﬁers, but are typically not desirable for voltage-controlled oscillators (VCO’s) nor analog-digital circuit functions due to their high noise corner frequencies and signiﬁcantly varying dc threshold voltage characteristics. On the other hand, the high linearity and low noise corner frequency characteristics of HBT’s make them ideal for high-efﬁciency linear power ampliﬁers as well as low-phase noise VCO applications, while their excellent dc current gain ( ) and threshold characteristics make them well suited for analog and digital applications as well. However, the HBT’s will fall short of providing state-of-the-art low-noise-ﬁgure ampliﬁers at microwave and Manuscript received February 18, 1997. This work was supported by the U.S. Air Force Wright Laboratory, Wright-Patterson AFB, OH 45433-7522 USA under Contract F33615-94-C-1560. The authors are with TRW Electronics Systems and Technology Division, Redondo Beach, CA 90278 USA. Publisher Item Identiﬁer S 1051-8207(97)05421-4. millimeter-wave frequencies above 10 GHz where low-noise HEMT devices are better suited. By monolithically integrating both HEMT’s and HBT’s on the same chip using an enabling technique called selective molecular beam epitaxy (MBE), the best device technology and circuit combinations can be realized, resulting in optimum circuit performance which is comparable to, or better than, equivalent hybrid implemen- tations. GaAs-based HEMT-HBT integration using selective MBE has previously been reported [1] with numerous MMIC demonstrations [2]–[9]. InP-based HEMT-HBT integration has recently demonstrated excellent dc and RF device performance which is equivalent to conventionally processed devices [10], [11]. In this letter, we describe an InP-based HEMT-HBT MMIC result which demonstrates the highest frequency per- formance so far obtained with any HEMT-HBT integrated technology. One major application of HEMT-HBT monolithic integra- tion is bias regulation for the HEMT MMIC. This need stems from the widely varying nature of the dc threshold voltage of HEMT devices. HEMT MMIC’s therefore typically require off-chip silicon bipolar regulators in order to maintain RF performance over process, temperature, and aging. Bipolar technologies such as HBT’s are more suitable for regula- tor circuits because of their uniform dc threshold and beta characteristics, high dc transconductance, and low dc power consumption. These properties are required for the low dc power and high gain op-amp bias regulator design. In typical HEMT MMIC applications, the size of the off- chip regulators can consume over 25 times the area of the actual HEMT MMIC [12]. Moreover, much of the module cost will be due to the assembly of several discrete wirebonds, resistors, and capacitors which are integrated with the silicon regulator and HEMT MMIC chips. At W-band, monolithic bias regulation is even more desirable because of the restric- tions on the size of the integrated microwave assembly (IMA), which must be small in order to prevent cavity moding effects which can degrade the RF performance at these extremely high frequencies. By monolithically integrating HBT bias regulation on the HEMT MMIC, the size and assembly cost can be reduced, and the RF cavity moding effects minimized. Although HBT regulated HEMT LNA MMIC’s have already been demonstrated with GaAs-based selective MBE [5], [13], this letter presents the ﬁrst report of an InP-based W-band HEMT ampliﬁer MMIC which monolithically integrates HBT bias regulation. 1051–8207/97$10.00  1997 IEEE