ADVANCED InP/InGaAs ELECTRONIC/OPTOELECTRONIC INTEGRATED CIRCUITS FOR HIGH SPEED MMIC APPLICATIONS

Abstract

The foundation of this research relied on the development and improvement of two key InP-based technologies, namely the Resonant Tunnelling Diode (RTD) and the Heterojunction Bipolar Transistor (HBT). This was firstly consolidated by a detailed experimental investigation of Double Barrier Quantum Well (DBQW) InGaAs/AlAs RTDs designed to improve the diode’s DC and RF characteristics through a design of experiments utilizing five different device structures targeting high current densities and large Peak to Valley Current Ratios (PVCR) for use in oscillator and amplifier ICs respectively. The measured results of the RTDs showed a significant increase in the current density with thinner barriers and quantum well widths. An estimated high frequency operation limit of 2.7THz was deduced for a 2×2 μm2 mesa RTD (sample #327). This device had a high current density JP of 10.8mA/μm2 while still maintaining an excellent PVCR ~5, one of the highest ever reported for such a high current density making the diode suitable for low-cost mm-wave/THz regime applications. In addition, a much more prominent finding is that of a very high negative differential conductance, 𝐺𝑅𝑇𝐷 of 95mS/μm2, the highest ever reported and largely responsible for the 2.7THz cut off frequency. An electromagnetic modelling of a 9μm2 InGaAs/AlAs RTD (sample #230) integrated with a CPW resonator predicts a 100 GHz fundamental frequency oscillator with an output power of 100μW. Furthermore, a novel K-band reflection based amplifier module was designed exploiting the NDR feature of RTD sample #277 incorporated with a lumped element branch coupler provided a high gain of 32 dB at 25.3 GHz while maintaining a μW level DC power consumption of 256μW. This corresponds to a record figure of merit of 125dB/mW, validating the excellent performance of the amplifier. An extensive study of an InP/InGaAs PIN-PD and SHBT modules employing large-signal built-in AGILENTHBT model from Keysight-ADS and opto-electrical equivalent circuit models extractions were undertaken. Those devices were fabricated and tested at the University of Manchester facility. Due to the specific design of the InP/InGaAs epilayer structures and considering the trade-off between high performance PIN and HBT to fulfil optimum 10 to 20Gb/s OEICs, a 10×10μm2 emitter mesa size transistor demonstrated an 𝑓𝑇 and 𝑓𝑚𝑎𝑥 of 54 and 57GHz respectively. The room temperature measurement for the PIN photodiode I-V characteristics with an optical window size of 20μm showed a low dark current of ~1.5nA under fully-depleted conditions. The measured photo-current was 41.5μA at -11dBm input optical power with a laser wavelength of λ=1.55μm, corresponding to a 0.5 A/W and 0.45 DC responsivity and quantum efficiency respectively without the use of antireflection coatings. The experimental data also revealed that the extracted high-frequency limit of 𝑅𝐶 time constant and carrier transit time were ~17.7 and 36GHz respectively. This is theoretically adequate for up to 25Gb/s operation and offering an outstanding feasibility for low cost OEICs for forthcoming generations 10Gb/s EPON (Ethernet Passive Optical Network) optical communication systems. An OEIC with single and multiple feedback loop topologies was modeled. The single feedback transimpedance amplifier, SFB-TIA exhibited a 32dBΩ transimpedance gain with a bandwidth of 14GHz and a series peaking inductor technique was used to further extend the -3dB bandwidth, contributing to widening the bandwidth to 18GHz. Since the conventional SFB-TIA has low optical overload response, a multiple feedback transimpedance amplifier, MFB-TIA circuit was therefore used which provided a gain of 45dBΩ with an electrical bandwidth exceeding 18GHz. This was achieved without the need for integrating a passive peaking element alongside producing deviation in the group delay of 11.7psec up to 20GHz. On-Off keying (OOK) NRZ 215-1 pseudo-random bit strea

Date of Award	1 Aug 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Mohamed Missous (Supervisor) & Max Migliorato (Supervisor)