The growing interest for 5G radios pushes technology development towards low-cost and high-performance solutions for operating at microwave and mm-wave. Downscaling CMOS technology has allowed the integration of high-speed transceivers on silicon chips, but high-power amplifiers rely on III-V technologies to deliver the power and efficiency levels required by modern radios.
In this work, we motivate the interest of non-Si technologies to meet 5G requirements, and we explore two routes to enable the fabrication of compound semiconductor devices on a large-scale manufacturable Si platform [1,2]. We provide insight on the potential of these new technologies for the design of advanced front-end modules, including modelling and reliability challenges.
In the first route (Figure 1(a)), we report on Al(Ga,In)N HEMTs, MISHEMTs and MOSFETs integrated on 200 mm Si wafers using Au-free processing in standard Si CMOS tools, and discuss the performance trade-offs, limitations and solutions. State-of-the-art contact resistance of 0.14 Ω.mm is demonstrated for a non-Au, low thermal budget (<600 oC) contact scheme, as well as a high vertical breakdown voltage (VBD) of >300 V. We show that MISHEMTs, which feature the highest field effect mobility (μFE), >2000 cm2/V.s, and the best 1/f noise performance, have the potential to outperform the other device types in terms of device scalability for high frequency operation. The GaN-on-Si substrate optimization for low RF losses and nonlinear distortion is further discussed.
The second route (Figure 1(b)) includes the formation of HBT on Si wafer by selective epitaxy. We demonstrate GaAs/InGaP HBTs grown on a 300 mm Si substrate. A DC current gain of ~112 and breakdown voltage, BVCBO, of 10 V is achieved. The emitter-base and base-collector diodes show an ideality factor of ~1.2 and ~1.4, respectively. This demonstration shows the potential for enabling a hybrid III-V CMOS/ technology for 5G and mm-wave applications, not limited to GaAs but which can also be extended to InGaAs on a 300 mm Si substrate.