Development of ultra-low power quantum-effect VCO MMICs based on an InP-based RTD/HBT IC fabrication technology

Abstract

In this dissertation, several types of ultra-low power quantum-effect VCOs using resonant-tunneling diodes (RTDs) have been proposed and implemented based on an InP-based RTD/HBT MMIC technology. The proposed RTD-based VCOs include fundamental-frequency VCOs such as a single-mode RTD VCO and a differential-mode RTD VCO, and a second-harmonic frequency push-push RTD VCO. Particularly, a push-push RTD VCO with a symmetric inductor instead of typically used dual inductors has been also implemented to exploit its area-reduction property. Compared to the conventional-type VCOs, the proposed RTD VCOs have shown ultra-low dc-power consumption properties with excellent figures of merit (FOMs) due to both the inherent negative differential resistance (NDR) characteristics and low bias voltage of the high-speed InP-based RTD. For the developed InP-based RTD/HBT MMIC technology, representative characteristics of the fabricated active devices are as follows. The RTD showed a peak voltage and current of 0.29 V and $0.73 kA/cm^{2}$, respectively, with a PVCR of 13. The cutoff frequency of the RTD was 61.4 GHz. The HBT with an emitter area of $1.5 \times 4 \mu m^{2}$ showed a peak $f_T/f_{max}$ of 100/63 GHz, respectively, with a maximum dc current gain of 95. As for passive devices, varactor diodes with various junction areas have been implemented by using a base-collector junction of the HBT. The spiral inductors with various turns and inductances were formed by using a top interconnect metal layer. The interdigitated capacitor used as a bypass capacitor was fabricated instead of a MIM capacitor due to the simple implementation. For practical IC applications, linear analyses for stabiliry criteria and temperature-dependent characterization have been conducted. In particular, a submicron-emitter RTD, targeted in this works, satisfied the stability criteria well due to the suppression of undesired oscillation modes. The temperature-dependent characteristics of Ka-band push-pu...