Improved shallow p+ diffusion into InGaAsP by a new spin-on diffusion source

Abstract

Shallow p+ diffusion into InGaAsP (λ=1.3 μm) has been improved by employing a new spin-on source based on Zn-doped alumina. Thereby the thermal expansion coefficients of diffusion source and semiconductor are better matched together than in case of the more common Zn-doped silica films. Consequently, besides an excellent mechanical stability of the spin-on films over a wide temperature range, the influence of mechanical stress on the diffusion process is effectively reduced. Applying diffusion temperatures around 600 °C surface hole concentrations above 6×1019 cm−3 and extremely low specific p-contact resistances of 2–3×10−6 Ω cm2 have been achieved.