Integration and fabrication of high-performance Sb-based heterostructure backward diodes with submicron-scale airbridges for terahertz detection

In this work, the authors report integration and fabrication of high-performance Sb-based heterostructure backward diodes (HBDs) with planar folded dipole antennas (FDAs) using submicron-scale airbridges for terahertz (THz) detection. By integrating HBDs into FDAs, high detector responsivity of 20 000 V/W at 200 GHz and 9500 V/W at 585 GHz could be potentially achieved due to the optimized impedance matching between the antenna and HBD detector. In order to minimize interconnect parasitics, the HBD integration is accomplished using submicron-scale airbridges. Electromagnetic simulations coupled to device models show that by introducing submicron-scale airbridges and optimizing the device layout, parasitic capacitance and spreading resistance can be significantly reduced. This allows performance nearly equal to the intrinsic device performance to be obtained. To achieve this level of performance, a novel fabrication and integration process has been developed. The process includes mix-and-match electron beam and optical lithography to span the size scales required for both the FDA and small-area HBDs, and offers high accuracy and reproducibility while requiring fewer critical fabrication steps compared to conventional hybrid integration techniques. Devices fabricated using this process have obtained a record-high device curvature coefficient of -58V(-1), indicating the quality of the devices that can be achieved. The process is scalable-in terms of device size, frequency range, and array size-enabling the development of THz focal plane arrays in a wide frequency range (100 GHz to beyond 1 THz). (C) 2016 American Vacuum Society.