Analysis of the active layer in SI GaAs Schottky diodes

The behavior of the active region width W of semi-insulating gallium arsenide Schottky diodes versus reverse biasing has been investigated by optical beam induced current and surface potential techniques. It has been found that at low applied voltages, W follows the square root law peculiar to a Schottky barrier while, for a bias higher than 20 V, the active layer increases linearly with the voltage applied. To go deeper into this matter, the spatial distribution of the electric field has been analyzed in a wide range of bias voltages and it has been observed that at high voltages a plateau occurs, followed by a linear decrease down to a quasi-zero value. In terms of space charge distribution this means that there is a box-shaped space charge region moving towards the ohmic contact at increasing bias.