Tiny amounts of cesium adsorbed on cleaved InSb(110) surfaces result in a strong downward band bending (BB) and creates a two-dimensional (2D) electron channel in the sub-surface region. For the first time, electron emission arising from this channel was observed for this material. We compare it to the similar situation mit previously with InAs(110). in this last case, new high-resolution measurements allow to determine the dispersions of the quantized energy levels, and to derive the average effective mass of the carriers in the channel. For both systems, self-consistent calculations and model-function curve fittings support the experimental results.