Selective etching during the electrochemical C-V profiling of PM-HEMTs

In this study we investigate the appearance of etch pits rind their effect on the ECV doping profiles of PM-HEMT structures grown by MOCVD and MBE. In some samples, etch-pits were observed after the etching of only 20 nm of t he top layer, The observed pits had a circular pattern with diameter rangin g from 2 to 25 mum. Study of these patterns by atomic force microscopy (AFM ) showed that they are holes with a depth varying from 0.3 to mum. The cont ribution of this hole area in the capacitance measurement during the ECV pr ocess results in the reduction and broadening of the observed peaks and in non reproducible profiling across the wafer. The dependence of the density; and dimensions of the etch-pits on the etching depth are also presented. ( C) 2001 Elsevier Science B.V. All rights reserved.