Enhancement of the Breakdown Voltage of GaAs/Al_xGa_<1-x>As Heterostructures for GaAs Metal-Semiconductor Field Effect Transistors Grown by Metalorganic Chemical Vapor Deposition

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We have studied enhancement of the breakdown voltage (BV) of epitaxial structures for GaAs metal-semiconductor field effect transistors (MESFETs) using GaAs/Al_xGa_<1-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 Al_xGa_<1-x>As layers and the ambient temperature (T=RT-200℃) was investigated. BV is much higher in the range of x>0.6. BV_i and BV_<sub> are maximum at 86.5V and 30V at 200℃ 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 Al_<0.8>Ga_<0.2>As buffer layer. The drain current-drain voltage (I_D-V_D) characteristics at 200℃ are superior to those at RT. Avalanche breakdown of I_D did not occur at V_D of less than 5 V.
社団法人応用物理学会の論文
1997-04-15