Surface passivation of GaAs MESFET's

The metal semiconductor field effect transistor (MESFET) represents a more realistic test for ''passivation'' efficacy than conventional capacitor test structures due to its prototypical fabrication process. This paper evaluates Gallium-Arsenide (GaAs) surface passivation films utilizing the MESFET as a test vehicle, For this study, gate-to-drain leakage current, gate-to-drain breakdown voltage, complex impedance versus frequency, and low-frequency noise measurements are performed on MESFET's with various passivation films. The results indicate that a hydrogen plasma used to ''pre-clean'' the GaAs surface in conjunction with an in situ plasma-enhanced chemical vapor deposition (PECVD) Si3N4 passivation film yields the best performance. In contrast, atomic-layer-epitaxial ZnSe demonstrated inferior performance (even in comparison to PECVD Si3N4 passivation films that did not receive a hydrogen ''pre-clean'').