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

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 6×10^{1 9}cm^-3 and extremely low specific p-contact resistances of 2-3×10^-6 Ωcm² have been achieved.