Effect of PECVD of SiO2 passivation layers on GaN and InGaP

Thin (200 Angstrom) layers of SiO2 were deposited by plasma enhanced chemical vapor deposition onto GaN and InGaP patterned with transmission line measurement contact pads. The sheet resistance of n-GaN and n- and p-InGaP was measured as a function of N2O/SiH4 ratio, rf chuck power, pressure and substrate temperature during the SiO2 deposition, The sheet resistance ratio before and after the deposition varied from 0.7 to 1.2, reflecting a competition between mechanisms that decrease doping (hydrogen passivation, ion-induced deep traps) and those that increase it (creation of shallow donor states in n-type material through preferential ion of the group V elements, gettering of hydrogen in p-type material). Under most conditions, SiO2 deposition creates minimal changes to the electrical properties of GaN and InGaP. (C) 2001 Published by Elsevier Science Ltd.