In this letter we report the measurement result of intrinsic carrier capture time in deep-etched quantum-box (70 nm diameter) lasers at low temperature (2 and 77 K). In order to investigate intrinsic carrier capture and relaxation mechanism, we have to rule out the contribution of the geometry factor and derive the local quantum capture time. For this purpose, lasers with the same box size (70 nm) but different box densities, that are arranged as two-dimensional periodic arrays for distributed feedback operations are prepared and measured. We find that the quantum capture time of the box lasers determined at 2 and 77 K is only about 2.4 ps and is smaller than the corresponding value of the quantum-well lasers. This is a direct experimental indication of the existence of an efficient channel for carrier capture and relaxation in the quantum-box system investigated. ©1997 American Institute of Physics.