The influence of the etched trenches on detection properties of strip GaAs detectors is described together with results obtained by transverse laser scan across the strips. The charge collection efficiency (CCE) shows an improvement in the case of trenches placed on the top (blocking) side of detector at lower bias voltages applied (<250 V), while noticeable worsen was observed in the case of bottom trenches. On the contrary, the energy resolution improved by the detectors with trenches either on the top or bottom side. Transverse scans across the top detector strips by pulsed red laser indicate different tendency of electric field development with bias voltage depending on the side of etching treatment.