This paper discusses crystal-growth and device-design issues associated with the development of high-performance InP/InGaAs heretostructure bipolar transistors (HBTs). It is shown that a highly Si-doped n+-subcollector in the HBT structure causes anomalous Zn redistribution during metalorganic vapor phase epitaxial (MOVPE) growth. A thermodynamical model of and a useful solution to this big problem are presented. A novel hybrid structure consisting of an abrupt emitter-base heterojunction and a compositionally-graded base is shown to enhance nonequilibrium base transport and thereby increase current gain and cutoff frequency fT. A double-heterostructure bipolar transistor (DHBT) with a step-graded InGaAsP collector can improve collector breakdown behavior without any speed penalty. We also elucidate the effect of emitter size shrinkage on high-frequency performance. Maximum oscillation frequency fmax in excess of 250 GHz is reported.

A wideband, low-power preamplifier and a high-speed, low-power monolithically integrated regenerative receiver are designed and fabricated using small-scale InP/InGaAs DHBTs. The preamplifier has a gain-bandwidth product of 192 GHz with a power dissipation of 51 mW. The regenerative receiver is successfully operated at 20 Gbit/s with a power dissipation of 0.6 W and an input dynamic range of 13 dB. This IC offers the lowest energy ever reported for regenerative receivers. In addition, a 20-Gbit/s optical modulator driver with a driving voltage of 2 V is successfully fabricated. These results demonstrate the feasibility of InP/InGaAs DHBTs for high-speed, low-power lightwave communication ICs.

Self-aligned InP/InGaAs heterojunction bipolar transistors (HBTs) were fabricated with emitter electrodes of 12, 22, 25, and 220 µm2 on the same wafer to investigate the influence of lateral scaling on device performance. DC characterization of these devices showed that InP/InGaAs HBTs are less subject to the emitter-size effect than GaAs-based HBTs. Common-emitter current gain β of the smallest 12-µm2 transistor was approximately 60 which is high enough for practical use. High-frequency characteristics of the transistors were almost the same in spite of the large difference in device size. Unity current-gain cutoff frequency fT of the smallest 12-µm2 transistor was as high as 163 GHz at a collector current of 2.3 mA, which ranks with the fT176 GHz achieved by the largest 220-µm2 transistor at a collector current of 45 mA. The smallest device also showed an excellent high-speed performance of fT100 GHz at submilliampere collector currents of Ic0.6 mA. The results indicate that small-lateral-dimension InP/InGaAs HBTs are applicable to high-speed ICs with low power dissipation.

A single-stage dual-frequency matching network that can simultaneously transform a transistor reflection coefficient to zero at two separate frequencies (a lower frequency fL and a higher frequency fH) is proposed. The network is made by adding a shorted stub, the length of which is a quarter-wavelength at fH, to a conventional L-section matching network composed of a series transmission line and an open stub. The concept of dual-frequency matching is based on the fact that the synthesized shunt admittance of the open and shorted stubs changes from capacitive at fH to inductive at fL. By means of the single-stage matching network, broad-band amplifier performance, the bandwidth of which is given as (fH-fL), can be easily obtained with almost the same design procedures and circuit area used for conventional narrow-band amplifiers. In this paper, the function of the dual-frequency matching network is analyzed in detail and an application of the matching technique to a two-stage amplifier is described. A broad-band performance of |S21|>7.4 dB at 27.0-62.5 GHz has been achieved with a GaAs P-HEMT two-stage MMIC amplifier.