Pulse duration dependence of single-shot pulsed laser ablation of gallium based III-V compound semiconductors

We experimentally study single-shot laser ablation of GaSb, GaAs, GaP and GaN, for laser pulse durations ranging from 200 fs to 20 ps. We find that the laser ablation threshold fluence of GaSb is almost independent of pulse duration, whereas the ablation threshold for GaN depends strongly on pulse duration. More generally we find that the larger the bandgap, the stronger the dependence of pulse duration. This is expected, as intrinsic laser absorption is mainly linear when the bandgap is small compared to the photon energy, whereas a larger bandgap requires strong field ionization. Thus a larger bandgap leads to a stronger influence of the peak intensity of the pulse and therefore a stronger dependence on the pulse duration, when compared to smaller bandgaps.