Quasi-vertical Schottky-structures for THZ-applications

Abstract

This paper presents the results of a systematical work on the improvement of high-frequency performance of quasi-vertical structures for THz-applications. Three versions of structure-design based on a quasi-vertical concept were successfully fabricated and characterized. The anti-parallel mixer-diode pair demonstrated a high performance at frequencies up to around 200 GHz. Measurements at frequencies about 600 GHz of a single diode structure mounted in a heterodyne mixer revealed a voltage responsivity of more than 1500 V/W and conversion loss (SSB) of bellow 10 dB. Microwave-noise measurements of such structure revealed typical values of the junction noise to be lower than 300 K at frequencies between 2.1 GHz and 4.8 GHz and at a bias current up to 3 mA. Low-frequency noise of these diodes is typically about 4 μV/Hz1/2 at 1 Hz. Achieved DC-characteristics are as follows: series resistance Rs < 7 Ω, ideality factor η < 1.2 and junction capacitance at 0 V C0j < 2.3 fF. The total capacitance of this structure is C0 < 7 fF. These data result in a calculated cut-off-frequency of well above 3 THz.