n‐Si/non‐liquid electrolyte interfaces have been realized in order to obtain electron accumulation layers of very high concentration at various temperatures. The interface has been characterized by using standard electrochemical measurements and the two‐dimensional electron gas has been studied by transconductance and infrared optical absorption measurements. These interfaces are found to exhibit densities as high as 4×1013electrons cm−2. These results are compared with available data on analogousn‐Si/organic‐solvent electrolyte interfaces.