Zh. Jin et al., HIGH-PERFORMANCE POLYCRYSTALLINE SIGE THIN-FILM TRANSISTORS USING AL2O3 GATE INSULATORS, IEEE electron device letters, 19(12), 1998, pp. 502-504
The use of aluminum oxide as the gate insulator for low temperature (6
00 degrees C) polycrystalline SiGe thin-film transistors (TFT's) has b
een studied. The aluminum oxide was sputtered from a pure aluminum tar
get using a reactive N2O plasma. The composition of the deposited alum
inum oxide was found to be almost stoichiometric (i.e., Al2O3), with a
very small fraction of nitrogen incorporation. Even without any hydro
gen passivation, good TFT performance was measured on devices with 50-
nm-thick Al2O3 gate dielectric layers. Typically, a field effect mobil
ity of 47 cm(2)/Vs, a threshold voltage of 3 V, a subthreshold slope o
f 0.44 V/decade, and an on/off ratio above 3 x 10(5) at a drain voltag
e of 0.1 V can be obtained, These results indicate that the direct int
erface between the Al2O3 and the SiGe channel layer is sufficiently pa
ssivated to make Al2O3 a better alternative to grown or deposited SiO2
for SiGe field effect devices.