Enhancement of the Breakdown Voltage of GaAs/AlxGa 1-xAs Heterostructures for GaAs Metal-Semiconductor Field Effect Transistors Grown by Metalorganic Chemical Vapor Deposition

Abstract

We have studied enhancement of the breakdown voltage (BV) of epitaxial structures for GaAs metal-semiconductor field effect transistors (MESFETs) using GaAs/Alx Ga1-x As heterostructures grown by metalorgnic chemical vapor deposition (MOCVD). The breakdown voltage (BV i) between FETs (lateral isolation) and the breakdown voltage (BV sub) of the epitaxial structure between FETs and substrates (vertical isolation) were mainly studied. The dependence of BV on the thickness (d), hole concentration (N A), AlAs mole fraction (x=0.3–1.0) of Alx Ga1-x As layers and the ambient temperature (T= RT–200° C) was investigated. BV is much higher in the range of x>0.6. BV i and BV sub are maximum at 86.5 V and 30 V at 200° C in the case of x=0.8, respectively. The enhancement of BV is attributed to a drastic decrease in N A with increasing x. The GaAs MESFETs were fabricated using an optimized epitaxial structure with an Al0.8Ga0.2As buffer layer. The drain current-drain voltage (I D–V D) characteristics at 200° C are superior to those at RT. Avalanche breakdown of I D did not occur at V D of less than 5 V.