Electron and hole impact ionization rates in bulk, superlattice, and sawtooth band structures consisting of an InAlGaAs system are determined from their photomultiplication characteristics. The impact ionization rate ratios are derived as 2.2, 3.0, and 3.6 for the bulk, superlattice and sawtooth structures, respectively, at an electric field of 470 kV/cm. The hole impact ionization rate in the InAlGaAs sawtooth structure is nearly equal to that of the InAlAs/InAlGaAs rectangular‐well superlattice. In contrast, the electron impact ionization rate in the sawtooth structure is larger than that in the superlattice. This difference is attributed to a lack of energy loss for electrons at the staircase band condition in the sawtooth structure. © 1994 American Institute of Physics.