Study and application of reactive ion etching on GaInP/InGaAs/GaInP quantum-well HEMTs

The gate recessing of a GaInP/InGaAs/GaInP quantum-weil HEMT (QHEMT) using pure BCl3 plasma is found improved by the addition of an appropriate amount of Ar to the gas flow. The influence of BCl3/Ar gas flow ratio on GaAs to GaInP etch selectivity, surface roughness and surface damage was determined. These results indicate that the conditions for minimum surface roughness, as determined by atomic force microscopy, corresponded with the conditions for minimum plasma damage. as determine by Raman spectroscopy. The best BCl3/Ar gas flow ratio for minimum surface damage and roughness was found to be 6:4 at a pressure of 60 mTorr with a 100 W RF power at this study. Two BCl3:Ar flow rate ratios, 6:4 and 10:0 (pure BCl3) were used to etch the gate recess in GaInP/InGaAs/GaInP QHEMT. From C-T measurements, it is found that the plasma-induced damage of the sample S-6:4 dry-etch with 6:4 BCl3/Ar is less than that of the sample S-10:0 dry-etched with pure BCl3. The d.c. characteristics of S-6:4 device was found to be superior to those of the wet-etched sample S-wet and S-10:0. In addition, the threshold voltage uniformity of sample SG:4 was found to be better than that of sample S-wet and sample S-10:0. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.