A G-Band Monolithically Integrated Quasi-Optical Zero-Bias Detector Based on Heterostructure Backward Diodes Using Submicrometer Airbridges

Abstract

This paper presents the design, fabrication, and characterization of a zero-bias quasi-optical terahertz detector based on monolithically integrated heterostructure backward diodes (HBDs) for operation at G-band. The reported detectors consist of HBDs with $0.7 \times 0.7 ~\mu \text{m}^{2}$ active device area and submicrometer-scale airbridges, integrated with lens-coupled high-impedance planar folded dipole antennas. Measurements of the HBD detector show that a peak-measured detector sensitivity of approximately 2400 V/W and a minimum noise equivalent power (NEPmin) of 2.14 pW/ $\surd $ Hz have been obtained at 170 GHz. If an antireflection coating was used on the lens, a sensitivity of approximately 3500 V/W and NEPmin of 1.48 pW/ $\surd $ Hz is projected. The radiation patterns of the quasi-optical detector in both $E$ - and $H$ -planes have been measured, and good agreement has been achieved between simulation and measurement. The performance of this detector can be further improved by scaling the HBD device active area. The reported approach using monolithically integrated heterostructure backward tunneling diodes and submicrometer airbridges is promising for developing high performance and compact detectors and focal-plane arrays for millimeter-wave and terahertz sensing and imaging applications.