Passivation of compound-semiconductor surfaces for low-noise terahertz devices

Abstract

Pt/n-GaAs Schottky varactor diode is an important nonlinear element for frequency multipliers in the submillimeter wavelengths. In the fabrication process, SiO 2-passivation is usually used to passivate the conductive active n-layer on the surface and reactive ion etching (RIE) technique is the standard technique to open Schottky contact area through the passivation. The main problem in the fabrication technique is to achieve the breakdown voltage as high as the avalanche breakdown theory predicts. Through optimization of the passivation and the RIE technique, we have successfully increased the breakdown voltage near the theoretical value and suppressed the excess noise resulted from the dry etching. Breakdown voltage of 18 and 9.5 V has been achieved with a doping level of 8×10 16 and 2.6×10 17 cm −3, respectively.