Thermally stable InGaP/GaAs Schottky contacts using low N content double layer WSiN

Abstract

This article describes thermally stable Schottky contacts using low N content double layered WSiN for InGaP/(In)GaAs metal–semiconductor field-effect transistors with self-aligned ion-implanted n+ layers. Transmission electron microscopy observations show that the microscopic interfacial reaction between WSiN and GaAs is completely suppressed when N content in the WSiN is 10% or less. As a result, a WSiN/GaAs-cap/InGaP Schottky contact shows high thermal stability after annealing at 800 °C for 100 min, even though the GaAs cap is as thin as 25 Å. Moreover, the double-layer WSiN structure suppresses reduction in the carrier concentration in the channel during activation annealing. The carrier concentration of the GaAs-cap (40 Å)/InGaP (100 Å)/ InGaAs-channel (100 Å) film, 6.5×1018 cm−3, decreases to less then 2×1018 cm−3 with low N content WSiN (N=10%, 4000 Å) after annealing at 900 °C for 0.1 s, but it remains 3.8×1018 cm−3 with the double layered WSiN (N=37%, 3800 Å/N=10%, 200 Å).