Fabrication process of InGaAs-based nanodiode array using electron-beam lithography technique

Abstract

Self-switching diode (SSD) is a unipolar two-terminal planar device which has a typical channel in nanoscale dimension. It has shown outstanding properties as a microwave and submillimeter wave rectifier by exploiting its nonlinear current-voltage (I-V) characteristic and intrisically low parasitic capacitance. In detection systems, SSDs are often used with an antenna to form a rectifying antenna (rectenna). The large impedance mismatch between SSD and antenna, due to high resistance of a single SSD, has always hampered the rectenna to achieve good extrinsic rectification performance (e.g., voltage responsivity > 400 V/W). As such, a large array of SSDs connected in parallel is very much desired to reduce the device resistance, and hence minimizing the impedance mismatching issue. In this work, an interdigital structure which can accommodate approximately 2,000 SSDs in parallel has been utilized. The material used was InGaAs/InAlAs heterostructure grown onto an InP substrate. The fabrication of the SSD array has implemented an electron-beam lithography (EBL) technique and the use of polymethyl methacrylate (PMMA) as a masking layer. The fabricated SSD array has shown a typical diode-like I-V characteristic, indicating that EBL method is not only convenient to realize nanoscale electronic devices, but also very practical for large area operations.