DC- and IF-noise performance optimization of GaAs Schottky diodes for THz applications

Abstract

This paper presents results which originated from a long-term systematic optimization of surface processing prior to anode formation of THz Schottky-based components. Particularly, four most promising surface-processing approaches are carefully investigated separately and in combination in order to understand the chemical and physical processes occurring on a GaAs surface. A reliable technological approach for anode formation is identified, which exhibits optimal diode characteristics and production repeatability. A model is proposed for the influence of each process on the subsequent one in the fabrication process sequence. DC-and IF-noise measurements are performed using an automated measurement system providing statistically significant data. Very good dc-parameters such as a series resistance of R s = 15 , an ideality factor N = 1.168, a reverse current I s = 0.024 fA and an IF-noise temperature of 257 K at 1 mA current bias with a good uniformity are achieved for non-cooled Schottky diodes with an anode diameter of 1 µm. The best noise figure is measured to be as low as 220 K at 3.8 GHz and 1 mA current bias.

RF and Thermal Design of Compound Semiconductor Devices using MEMS Approach

“…The optimization of these parameters requires technology optimization as well as a THz capable device design as described in [12]. 5, is used as the basic approach for modeling of DC properties because it takes the influence of impurities and irregularities at the interface into account (Fermi-level pinning), which have been shown to be relevant for the applied technology [13][14][15].The entire model consists of the intrinsic model, which analytically models interface properties (i.e. Beyond the analytic description of the barrier, the intrinsic model includes the epi-layer resistance and a frequency dependent substrate resistance taking the skin effect into account (proposed by Dickens [16]).…”

A new structural approach for uniform sub-micrometer anode metallization of planar THz Schottky components

“…It is well known that surface defects and contamination hinder the formation of the desired barrier heights and crucially reduce the reliability of the device. An investigation of the etching parameters and of post-RIE (reactive ion etching) treatment methods was performed to reduce the excess noise due to the RIE process during anode opening [2,3]. Additional important conditions for the formation of a good Schottky contact are the selection of a suitable contact metal and its associated deposition method.…”

“…Metal deposition is controlled using different parameters such as the electrolyte concentration and temperature of the bath, pulse width, period and amplitude, sample size and impedance [12,13]. This method gives good repeatable results with respect to dc and RF performances of these devices [3,14].…”