Improving InP DHBT linearity for subTHz broadband operation

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The sub-mm-wave and THz frequency range is gaining interest for wide ranging applications in wireless communication, material sensing, nondestructive testing, biology and agriculture, as well as near-surface medical imaging. Electronic systems are widely seen as a key to widespread adoption of mm-wave and THz applications, offering cw operation, low size and weight, high robustness, and low power consumption. For wireless communications, a vast amount of spectrum in the atmospheric windows around 140 GHz and 300 GHz exists and is being made available for commercial use through standardization bodies. There are many other industrially relevant uses for linear wideband circuits at mm-wave and THz frequencies, e.g. instrumentation, which have a large industrial base in Europe. Advancement in this area therefore directly benefits the national and European technological sovereignty. To take advantage of the available spectrum, wireless transmitters with sufficient RF output power to overcome the high losses at those frequencies are needed. Increased transistor linearity enables a reduction of amplifier back-off and thus translates into higher system power efficiency and/or increased useable transmitted power and therefore increased transmission distance in future communication systems. A better and more fundamental understanding of THz transistor linearity is paramount to finding technological answers to the requirements of 300 GHz wireless systems. The Indium Phosphide Double-Heterostructure Bipolar Transistor (InP DHBT) is - in comparison to other available transistor technologies - very well suited for RF power amplifiers, mixers and other wideband circuits. InP exhibits a breakdown field similar to silicon, whilst a higher electron velocity in InP enables a relatively thick collector design and thus high breakdown voltage. However, the base-collector heterojunction and high collector current densities impede the linearity performance of the devices. For amplification and mixing functions in future wideband 6G transceivers operating at 300 GHz, optimized InP HBT structures are needed, in conjunction with accurate physical simulation and compact device modeling for circuit design. This project aims to not only improve the linearity of InP DHBT devices through optimization of the composition of the base-collector junction, but also at comprehensive analysis and understanding of the underlying physical mechanisms. Based on the insights gained within the project, highly linear InP DHBTs shall be demonstrated and the respective compact model enabling circuit desing shall be derived.