The research focused on evaluating the feasibility into Microwave Monolithic Integrated Circuits (MMIC) fabrication capability, in the UK, using novel material type: all ternary In0.52Al0.48As/In0.53Ga0.47As lattice matched to InP substrate double heterojunction bipolar transistor (DHBT) technology; with the potential for providing high speed HBTs. The demonstration of a MMIC capability would follow with the development of a BiFET process that would satisfy SELEX Galileo circuit business needs. The research project complexity is divide into 5 phases: phase 1, the development of a high frequency In0.52Al0.48As / In0.53Ga0.47As lattice matched to InP substrate DHBT technology; phase 2, development of passive components; phase 3, the creation of two VBIC physical models; phase 4, the creation of a Process Development Kit (PDK) and phase 5, the design, simulation and fabrication of a divide-by-2 frequency divider using the technology developed in phase 1. Phase 1, concluded with a DHBT epitaxial design and fabrication that produced devices with a peak high frequency performance f_t = 140GHz and f_max = 95GHz at a current density Jc ≈ 1mA/µm2. This was achieved through the optimisation of the epitaxial design to reduce the base transit time τb through the introduction of a quasi electric field and thinning of base layer. To the best of the author’s knowledge, this is the highest f_t performance for a 1µm emitter width all ternary In0.52Al0.48As / In0.53Ga0.47As DHBT. The design, simulation and fabrication of a divide-by-2 frequency divider were only made possible by the successfully development of passive components (phase 2) and the VBIC model and PDK creation (phase 3 and 4). The divide-by-2 frequency divider design and simulation was done via the use of the PDK. The simulations resulted in a divide-by-2 frequency divider with a maximum operating frequency of 27GHz at a minimum input power of 2dBm. The fabrication of the MMIC resulted in a transistor component yield of 69%, which unfortunately resulted in a divide-by-2 frequency divider circuit yield of 0%. The fabrication of MMIC circuits is not possible with current state of the fabrication environment; however the only obstacle the University of Manchester (UoM) faces is low active component yield. To increase the active component yield to the 95% level required for high circuit yields, large capital investment into the fabrication equipment and human time into setting up the fabrication process to a repeatable and reliable standard is required.

In this thesis, a detailed study of the electrical and optical characterisations of Heterojuction Bipolar Transistors (HBTs) for optical detection is presented. By comparing both DC and optical characterisations between In0.49Ga0.51P/GaAs Single Heterojuction Bipolar Transistors (SHBTs) and Double Heterojuction Bipolar Transistors (DHBTs), the advantages of using the DHBT as a short wavelength detector are shown. Phenomena related to the base region energy band bending in the DHBT caused by a self-induced effective electric field is discussed and its effects on the performance of the device are elaborated. The use of an eye diagram has been employed to provide requisite information for performance qualification of SHBT/DHBT devices. These give a more detailed understanding compared to conventional S-parameters method. A detailed comparison of In0.49Ga0.51P/GaAs SHBT and DHBT performance using an eye diagram as a functional tool by adopting a modified T-shaped small signal equivalent circuit are given. By adopting this modified T-shaped small signal equivalent circuit, the use of In0.49Ga0.51P/GaAs Double Heterojuction Phototransistors (DHPT) as a short wavelength photodetector is analysed. It is therefore shown that an eye diagram can act as a powerful tool in HBTs/HPTs design optimisations, for the first time in this work. In order to predict the spectral response (SR) and optical characterisations of GaAs-based HPTs, a detailed theoretical absorption model is also presented. The layer dependence of an optical flux absorption profile, along with doping dependent absorption coefficients are taken into account for the optical characterisation prediction. With the aim of eliminating the limitation of current gain as a prerequisite, analytical modelling of SR has been developed by resolving the continuity equation and applying realistic boundary conditions. Then, related physical parameters and a layer structure profile are used to implement simulations. A good agreement with the measured results of the Al0.3Ga0.7As/GaAs HPT is shown validating the proposed theoretical model.

The proposed research is for a novel SiGe-based Ion-Sensitive Dual Hetero-junction Bipolar Transistor (IS-HBT) to be used in both trans-dermal biological sensing as well as Lab-on-Chip (LOC) applications. The end goals for the device designed are two: For one, the research done for this work will be used to substantiate the claims made by Zafar et al. [1] that an HBT-style structure is better suited for biosensing application rather than a conventional Field Effect Transistor (FET) based geometries. Secondly, it provides the final element to be integrated along with a selectivity membrane, as well as with a reverse-iontophoresis system to enact trans-dermal sensing of potassium ions in a wearer’s body. The novelty of the device stems from the proposed modified wedding-cake structure lending itself to be easily implemented in a wearable package, the fact that it will act as both a transduction device as well as provide preamplification of signals. If successful, future researchers and/or corporations will have at their disposal a label-free advanced biosensor design that is integration-ready with currently available standard SiGe-BiCMOS processes.