Heterogeneous Integration [From the Guest Editors' Desk

Abstract

Today, there is ever-increasing interest in employing unused electromagnetic spectra and taking advantage of millimeter-wave (mmW) and submillimeter-wave (submmW) or terahertz (THz) frequencies. Current, rapid advances in semiconductor and packaging technologies along with the commercial availability of test equipment up to 1 THz have enabled many important developments at these high-frequency bands. As a result, next-generation broadband and ultrahigh-speed wireless communication systems, high-resolution imagers and sensors, and automotive radars will operate at mmW and sub-mmW regions, which will demand increasingly complex functionalities with better performance, compactness, efficiency, and reliability at a low cost. For semiconductor technologies, silicon (Si) is the dominant material in terms of circuit functionality, complex integration, maturity and yield, and cost. Further, recently integrated Si RF technologies—complementary–metal-oxide semiconductor (CMOS) and bipolar junction transistor/CMOS (BiCMOS)—have made tremendous progress in power, while frequencies have been extended to around 100 GHz. However, there are still applications that can be fulfilled only by compound semiconductor (CS) technology, such as indium phosphide (InP), which provides transistors with fmax of 1 THz, high gain and power, and mixed signal circuits with ultrahigh speed, and gallium nitride (GaN), which enables devices with wide bandwidth, high breakdown voltage, and output power up to 100 GHz. Therefore, integration of dissimilar semiconductors.