Why choose InGaAs over Germanium?
The choice of detector is affected by several parameters: beam size, power and wavelength. In general a photodiode will give best results when used at wavelengths below the wavelength of peak sensitivity. Although the head may operate at higher wavelengths, the sensitivity of the photodiode will be strongly temperature dependant. Thus, for wavelengths beyond 1550nm, InGaAs will be the material of choice.
Also, at wavelengths below 800nm, our visible enhance InGaAs exhibits markedly higher responsivity than Germanium.
On the downside, large area InGaAs detectors are prohibitively expensive. Thus, this material is generally limited to ø3mm sensitive area.