Thin (200 Angstrom) layers of SiO2 were deposited by plasma enhanced chemic
al vapor deposition onto GaN and InGaP patterned with transmission line mea
surement 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 sub
strate temperature during the SiO2 deposition, The sheet resistance ratio b
efore and after the deposition varied from 0.7 to 1.2, reflecting a competi
tion between mechanisms that decrease doping (hydrogen passivation, ion-ind
uced deep traps) and those that increase it (creation of shallow donor stat
es in n-type material through preferential ion of the group V elements, get
tering of hydrogen in p-type material). Under most conditions, SiO2 deposit
ion creates minimal changes to the electrical properties of GaN and InGaP.
(C) 2001 Published by Elsevier Science Ltd.