Determination of surface potential of GaN:Si

The surface potential of GaN:Si is determined for Si doping from 2.4 x 10(exp 17) cm-3 to 2.3 x 10(exp 19) cm-3 in layers grown by low pressure metal-organic vapor-phase epitaxy. We used the sheet resistance of the samples with different thickness measured by eddy current, a non-destructive, contactless method, to determine the depleted region. From the width of the depletion layer, which is dependent on the doping concentration, measured by secondary ion mass spectrometry, we obtained the GaN:Si surface potential on the basis of the depletion approximation. The surface potential decreases with increasing carrier concentration from about 1.6 eV down to 0.2 eV. Based on the behavior of the surface potential with doping we determined the surface state density.