It is a key challenge for membrane photonic devices to have ohmic contacts with both low optical loss and low contact resistance. In this paper, we present novel n-type ohmic contacts to InP-based membranes based on AgGe, showing low absorption loss and good thermal stability. By using heavily doped InGaAs(P) as contact layers, annealing-free ohmic contacts with specific contact resistances in the level of 10-7 Ω cm2 are obtained. Furthermore, strong bandfilling effects in these contact layers result in low optical absorption. Compared to conventional AuGeNi contacts, this new solution gives an order of magnitude reduction in the propagation loss measured in membrane waveguides.