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

Pt/n-GaAs Schottky varactor diode is an important nonlinear element for fre quency multipliers in the submillimeter wavelengths. In the fabrication pro cess, SiO2-passivation is usually used to passivate the conductive active n -layer on the surface and reactive ion etching (RIE) technique is the stand ard technique to open Schottky contact area through the passivation. The ma in problem in the fabrication technique is to achieve the breakdown voltage as high as the avalanche breakdown theory predicts. Through optimization o f the passivation and the RIE technique, we have successfully increased the breakdown voltage near the theoretical value and suppressed the excess noi se resulted from the dry etching. Breakdown voltage of 18 and 9.5 V has bee n achieved with a doping level of 8 x 10(16) and 2.6 x 10(17) cm(-3), respe ctively. (C) 2000 Elsevier Science Ltd. All rights reserved.