We have investigated the laser interference crystallization ͑LIC͒ of amorphous germanium films on ͑100͒-oriented GaAs substrates using nanosecond laser pulses. We demonstrate that LIC can produce periodic arrays of epitaxially crystallized Ge lines on GaAs with submicrometer widths. The gratings display a surface undulation with faceted surfaces, which depends on laser fluency. The undulation is attributed to the lateral solidification process induced by the temperature gradients created during the LIC process.