CHARACTERIZATION OF ELECTRICAL DAMAGE-INDUCED BY CH4 H-2 REACTIVE IONETCHING OF MOLECULAR-BEAM EPITAXIAL INALAS/

In this article, we report investigations on the effects of methane/hy drogen (CH4/H-2) reactive ion etching (RTE) of InGaAs/InAlAs/InP heter ostructure materials for high electron mobility transistors, and espec ially on the electrical properties of the InAlAs layer after dry reces s etching of the InGaAs cap layer. The ion etching induced damages in the barrier layer InAlAs are evaluated by diode current-voltage and ca pacitance-voltage measurements and deep-level transient spectroscopy ( DLTS). The I-V data indicate that RTE lowers the Schottky barrier heig ht (phi(b)) and increases the ideality factor. Using low pressure (10 mTorr) RIE processes, with various self-bias voltages, shows that the use of low ion energy is necessary to get good Schottky contacts. Rapi d thermal annealing at 400 degrees C is shown to induce a limited decr ease of the dry etching induced defects. However, full recovery of the electrical properties is not achieved. A significant improvement of t he Schottky diode electrical characteristics and DLTS spectra is obser ved after wet etching a 60 Angstrom thick InAlAs layer before metal de position, indicating that the main damages are concentrated within a s hort distance from the surface. (C) 1996 American Vacuum Society.