Self-aligned technology for tungsten-contacted InP-based etched mesa laser devices

Abstract

The characteristics of W metallization for use as self-aligned ohmic contacts and selective area etching and regrowth masks on InP-based laser structures are reported. rf-sputtered W films under either compressive or tensile stress were examined. Mesas for epitaxial regrowth were obtained by CF4/O2 dry etching of the previously deposited W film, followed either by HBr/H2O2/H2O wet chemical etching or CH4/H2/Ar electron cyclotron resonance plasma etching of ∼4 μm of InP. The W film preserved its inert metallurgical nature while heated under PH3/H2 ambient at 700 °C for 20 min, simulating the standard regrowth conditions. The W contacts on n-InP (n=5×1018 cm−3) substrates yielded stable, low contact resistivity (0.2 Ω cm) after rapid thermal processing at 600–700 °C.