Abstract Electronic structures in heterojunctions are determined by a semi-empirical method starting from samples in which both ground and first-excited subbands are occupied by electrons. The characteristics of the GaInAs/InP system are investigated and compared with those in the GaAs/AlGaAs system. Differences in material parameters such as band gaps, band discontinuities and electron effective masses affect the two-dimensional subband structure. As a result, electron confinement in the former system becomes weaker that that in the latter and the first-excited subband is easily occupied by electrons.